The Enzyme Database

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EC 1.1.1.84     
Accepted name: dimethylmalate dehydrogenase
Reaction: (R)-3,3-dimethylmalate + NAD+ = 3-methyl-2-oxobutanoate + CO2 + NADH
For diagram of pantothenate catabolism, click here
Other name(s): β,β-dimethylmalate dehydrogenase
Systematic name: (R)-3,3-dimethylmalate:NAD+ oxidoreductase (decarboxylating)
Comments: Requires K+ or NH4+ and Mn2+ or Co2+; also acts on (R)-malate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37250-21-8
References:
1.  Magee, P.T. and Snell, E.E. The bacterial degradation of pantothenic acid. IV. Enzymatic conversion of aldopantoate to α-ketoisovalerate. Biochemistry 5 (1966) 409–416. [PMID: 4287371]
[EC 1.1.1.84 created 1972]
 
 
EC 1.1.1.345     
Accepted name: D-2-hydroxyacid dehydrogenase (NAD+)
Reaction: an (R)-2-hydroxycarboxylate + NAD+ = a 2-oxocarboxylate + NADH + H+
Other name(s): LdhA; HdhD; D-2-hydroxyisocaproate dehydrogenase; R-HicDH; D-HicDH; (R)-2-hydroxy-4-methylpentanoate:NAD+ oxidoreductase; (R)-2-hydroxyisocaproate dehydrogenase; D-mandelate dehydrogenase (ambiguous)
Systematic name: (R)-2-hydroxycarboxylate:NAD+ oxidoreductase
Comments: The enzymes, characterized from bacteria (Peptoclostridium difficile, Enterococcus faecalis and from lactic acid bacteria) prefer substrates with a main chain of 5 carbons (such as 4-methyl-2-oxopentanoate) to those with a shorter chain. It also utilizes phenylpyruvate. The enzyme from the halophilic archaeon Haloferax mediterranei prefers substrates with a main chain of 3-4 carbons (pyruvate and 2-oxobutanoate). cf. EC 1.1.1.272, (D)-2-hydroxyacid dehydrogenase (NADP+).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Dengler, U., Niefind, K., Kiess, M. and Schomburg, D. Crystal structure of a ternary complex of D-2-hydroxyisocaproate dehydrogenase from Lactobacillus casei, NAD+ and 2-oxoisocaproate at 1.9 Å resolution. J. Mol. Biol. 267 (1997) 640–660. [DOI] [PMID: 9126843]
2.  Bonete, M.J., Ferrer, J., Pire, C., Penades, M. and Ruiz, J.L. 2-Hydroxyacid dehydrogenase from Haloferax mediterranei, a D-isomer-specific member of the 2-hydroxyacid dehydrogenase family. Biochimie 82 (2000) 1143–1150. [DOI] [PMID: 11120357]
3.  Kim, J., Darley, D., Selmer, T. and Buckel, W. Characterization of (R)-2-hydroxyisocaproate dehydrogenase and a family III coenzyme A transferase involved in reduction of L-leucine to isocaproate by Clostridium difficile. Appl. Environ. Microbiol. 72 (2006) 6062–6069. [DOI] [PMID: 16957230]
4.  Wada, Y., Iwai, S., Tamura, Y., Ando, T., Shinoda, T., Arai, K. and Taguchi, H. A new family of D-2-hydroxyacid dehydrogenases that comprises D-mandelate dehydrogenases and 2-ketopantoate reductases. Biosci. Biotechnol. Biochem. 72 (2008) 1087–1094. [DOI] [PMID: 18391442]
5.  Chambellon, E., Rijnen, L., Lorquet, F., Gitton, C., van Hylckama Vlieg, J.E., Wouters, J.A. and Yvon, M. The D-2-hydroxyacid dehydrogenase incorrectly annotated PanE is the sole reduction system for branched-chain 2-keto acids in Lactococcus lactis. J. Bacteriol. 191 (2009) 873–881. [DOI] [PMID: 19047348]
6.  Miyanaga, A., Fujisawa, S., Furukawa, N., Arai, K., Nakajima, M. and Taguchi, H. The crystal structure of D-mandelate dehydrogenase reveals its distinct substrate and coenzyme recognition mechanisms from those of 2-ketopantoate reductase. Biochem. Biophys. Res. Commun. 439 (2013) 109–114. [DOI] [PMID: 23954635]
[EC 1.1.1.345 created 2013]
 
 
EC 1.1.1.397     
Accepted name: β-methylindole-3-pyruvate reductase
Reaction: (2S,3R)-2-hydroxy-3-(indol-3-yl)butanoate + NAD+ = (R)-3-(indol-3-yl)-2-oxobutanoate + NADH + H+
Glossary: (R)-3-(indol-3-yl)-2-oxobutanoate = (R)-β-methylindole-3-pyruvate
(2S,3R)-2-hydroxy-3-(indol-3-yl)butanoate = indolmycenate
Other name(s): ind2 (gene name)
Systematic name: (2S,3R)-2-hydroxy-3-(indol-3-yl)butanoate:NAD+ oxidoreductase
Comments: The enzyme, characterized from the bacterium Streptomyces griseus, participates in the biosynthesis of indolmycin, an antibacterial drug that inhibits the bacterial tryptophan—tRNA ligase (EC 6.1.1.2).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Du, Y.L., Alkhalaf, L.M. and Ryan, K.S. In vitro reconstitution of indolmycin biosynthesis reveals the molecular basis of oxazolinone assembly. Proc. Natl. Acad. Sci. USA 112 (2015) 2717–2722. [DOI] [PMID: 25730866]
[EC 1.1.1.397 created 2016]
 
 
EC 1.1.1.410     
Accepted name: D-erythronate 2-dehydrogenase
Reaction: D-erythronate + NAD+ = 2-dehydro-D-erythronate + NADH + H+
For diagram of erythronate and threonate catabolism, click here
Glossary: D-erythronate = (2R,3R)-2,3,4-trihydroxybutanoate
2-dehydro-D-erythronate = (3R)-3,4-dihydroxy-2-oxobutanoate
Other name(s): denD (gene name)
Systematic name: D-erythronate:NAD+ 2-oxidoreductase
Comments: The enzyme, characterized from bacteria, is involved in D-erythronate catabolism.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Zhang, X., Carter, M.S., Vetting, M.W., San Francisco, B., Zhao, S., Al-Obaidi, N.F., Solbiati, J.O., Thiaville, J.J., de Crecy-Lagard, V., Jacobson, M.P., Almo, S.C. and Gerlt, J.A. Assignment of function to a domain of unknown function: DUF1537 is a new kinase family in catabolic pathways for acid sugars. Proc. Natl. Acad. Sci. USA 113 (2016) E4161–E4169. [DOI] [PMID: 27402745]
[EC 1.1.1.410 created 2017]
 
 
EC 1.1.1.411     
Accepted name: L-threonate 2-dehydrogenase
Reaction: L-threonate + NAD+ = 2-dehydro-L-erythronate + NADH + H+
For diagram of erythronate and threonate catabolism, click here
Glossary: L-threonate = (2R,3S)-2,3,4-trihydroxybutanoate
2-dehydro-L-erythronate = (3R)-3,4-dihydroxy-2-oxobutanoate
Other name(s): ltnD (gene name)
Systematic name: L-threonate:NAD+ 2-oxidoreductase
Comments: The enzyme, characterized from bacteria, is involved in L-threonate catabolism.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Zhang, X., Carter, M.S., Vetting, M.W., San Francisco, B., Zhao, S., Al-Obaidi, N.F., Solbiati, J.O., Thiaville, J.J., de Crecy-Lagard, V., Jacobson, M.P., Almo, S.C. and Gerlt, J.A. Assignment of function to a domain of unknown function: DUF1537 is a new kinase family in catabolic pathways for acid sugars. Proc. Natl. Acad. Sci. USA 113 (2016) E4161–E4169. [DOI] [PMID: 27402745]
[EC 1.1.1.411 created 2017]
 
 
EC 1.1.1.428     
Accepted name: 4-methylthio 2-oxobutanoate reductase (NADH)
Reaction: (2R)-2-hydroxy-4-(methylsulfanyl)butanoate + NAD+ = 4-(methylsulfanyl)-2-oxobutanoate + NADH + H+
Other name(s): CTBP1 (gene name); C-terminal-binding protein 1; MTOB reductase; 4-methylthio 2-oxobutyrate reductase; 4-methylthio 2-oxobutyric acid reductase
Systematic name: (2R)-2-hydroxy-4-(methylsulfanyl)butanoate:NAD+ 2-oxidoreductase
Comments: The substrate of this enzyme is formed as an intermediate during L-methionine salvage from S-methyl-5′-thioadenosine, which is formed during the biosynthesis of polyamines. The human enzyme also functions as a transcriptional co-regulator that downregulates the expression of many tumor-suppressor genes, thus providing a link between gene repression and the methionine salvage pathway. A similar, but NADP-specific, enzyme is involved in dimethylsulfoniopropanoate biosynthesis in algae and phytoplankton.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Kumar, V., Carlson, J.E., Ohgi, K.A., Edwards, T.A., Rose, D.W., Escalante, C.R., Rosenfeld, M.G. and Aggarwal, A.K. Transcription corepressor CtBP is an NAD+-regulated dehydrogenase. Mol. Cell 10 (2002) 857–869. [DOI] [PMID: 12419229]
2.  Achouri, Y., Noel, G. and Van Schaftingen, E. 2-Keto-4-methylthiobutyrate, an intermediate in the methionine salvage pathway, is a good substrate for CtBP1. Biochem. Biophys. Res. Commun. 352 (2007) 903–906. [DOI] [PMID: 17157814]
3.  Hilbert, B.J., Grossman, S.R., Schiffer, C.A. and Royer, W.E., Jr. Crystal structures of human CtBP in complex with substrate MTOB reveal active site features useful for inhibitor design. FEBS Lett. 588 (2014) 1743–1748. [DOI] [PMID: 24657618]
4.  Korwar, S., Morris, B.L., Parikh, H.I., Coover, R.A., Doughty, T.W., Love, I.M., Hilbert, B.J., Royer, W.E., Jr., Kellogg, G.E., Grossman, S.R. and Ellis, K.C. Design, synthesis, and biological evaluation of substrate-competitive inhibitors of C-terminal Binding Protein (CtBP). Bioorg. Med. Chem. 24 (2016) 2707–2715. [DOI] [PMID: 27156192]
[EC 1.1.1.428 created 2022]
 
 
EC 1.2.1.25     
Accepted name: branched-chain α-keto acid dehydrogenase system
Reaction: 3-methyl-2-oxobutanoate + CoA + NAD+ = 2-methylpropanoyl-CoA + CO2 + NADH
Other name(s): branched-chain α-keto acid dehydrogenase complex; 2-oxoisovalerate dehydrogenase; α-ketoisovalerate dehydrogenase; 2-oxoisovalerate dehydrogenase (acylating)
Systematic name: 3-methyl-2-oxobutanoate:NAD+ 2-oxidoreductase (CoA-methylpropanoylating)
Comments: This enzyme system catalyses the oxidative decarboxylation of branched-chain α-keto acids derived from L-leucine, L-isoleucine, and L-valine to branched-chain acyl-CoAs. It belongs to the 2-oxoacid dehydrogenase system family, which also includes EC 1.2.1.104, pyruvate dehydrogenase system, EC 1.2.1.105, 2-oxoglutarate dehydrogenase system, EC 1.4.1.27, glycine cleavage system, and EC 2.3.1.190, acetoin dehydrogenase system. With the exception of the glycine cleavage system, which contains 4 components, the 2-oxoacid dehydrogenase systems share a common structure, consisting of three main components, namely a 2-oxoacid dehydrogenase (E1), a dihydrolipoamide acyltransferase (E2), and dihydrolipoamide dehydrogenase (E3). The reaction catalysed by this system is the sum of three activities: EC 1.2.4.4, 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring), EC 2.3.1.168, dihydrolipoyllysine-residue (2-methylpropanoyl)transferase, and EC 1.8.1.4, dihydrolipoyl dehydrogenase. The system also acts on (S)-3-methyl-2-oxopentanoate and 4-methyl-2-oxopentanoate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37211-61-3
References:
1.  Namba, Y., Yoshizawa, K., Ejima, A., Hayashi, T. and Kaneda, T. Coenzyme A- and nicotinamide adenine dinucleotide-dependent branched chain α-keto acid dehydrogenase. I. Purification and properties of the enzyme from Bacillus subtilis. J. Biol. Chem. 244 (1969) 4437–4447. [PMID: 4308861]
2.  Pettit, F.H., Yeaman, S.J. and Reed, L.J. Purification and characterization of branched chain α-keto acid dehydrogenase complex of bovine kidney. Proc. Natl. Acad. Sci. USA 75 (1978) 4881–4885. [DOI] [PMID: 283398]
3.  Harris, R.A., Hawes, J.W., Popov, K.M., Zhao, Y., Shimomura, Y., Sato, J., Jaskiewicz, J. and Hurley, T.D. Studies on the regulation of the mitochondrial α-ketoacid dehydrogenase complexes and their kinases. Adv. Enzyme Regul. 37 (1997) 271–293. [DOI] [PMID: 9381974]
4.  Evarsson, A., Chuang, J.L., Wynn, R.M., Turley, S., Chuang, D.T. and Hol, W.G. Crystal structure of human branched-chain α-ketoacid dehydrogenase and the molecular basis of multienzyme complex deficiency in maple syrup urine disease. Structure 8 (2000) 277–291. [PMID: 10745006]
5.  Reed, L.J. A trail of research from lipoic acid to α-keto acid dehydrogenase complexes. J. Biol. Chem. 276 (2001) 38329–38336. [DOI] [PMID: 11477096]
[EC 1.2.1.25 created 1972, modified 2019, modified 2020]
 
 
EC 1.2.4.3      
Deleted entry:  2-oxoisocaproate dehydrogenase. Now included with EC 1.2.4.4, 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring)
[EC 1.2.4.3 created 1972, deleted 1978]
 
 
EC 1.2.4.4     
Accepted name: 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring)
Reaction: 3-methyl-2-oxobutanoate + [dihydrolipoyllysine-residue (2-methylpropanoyl)transferase] lipoyllysine = [dihydrolipoyllysine-residue (2-methylpropanoyl)transferase] S-(2-methylpropanoyl)dihydrolipoyllysine + CO2
For diagram of oxo-acid-dehydrogenase complexes, click here
Glossary: dihydrolipoyl group
thiamine diphosphate = 3-[(4-amino-2-methylpyrimidin-5-yl)methyl]-5-(2-diphosphoethyl)-4-methyl-1,3-thiazolium
Other name(s): 2-oxoisocaproate dehydrogenase; 2-oxoisovalerate (lipoate) dehydrogenase; 3-methyl-2-oxobutanoate dehydrogenase (lipoamide); 3-methyl-2-oxobutanoate:lipoamide oxidoreductase (decarboxylating and acceptor-2-methylpropanoylating); α-keto-α-methylvalerate dehydrogenase; α-ketoisocaproate dehydrogenase; α-ketoisocaproic dehydrogenase; α-ketoisocaproic-α-keto-α-methylvaleric dehydrogenase; α-ketoisovalerate dehydrogenase; α-oxoisocaproate dehydrogenase; BCKDH (ambiguous); BCOAD; branched chain keto acid dehydrogenase; branched-chain (-2-oxoacid) dehydrogenase (BCD); branched-chain 2-keto acid dehydrogenase; branched-chain 2-oxo acid dehydrogenase; branched-chain α-keto acid dehydrogenase; branched-chain α-oxo acid dehydrogenase; branched-chain keto acid dehydrogenase; branched-chain ketoacid dehydrogenase; dehydrogenase, 2-oxoisovalerate (lipoate); dehydrogenase, branched chain α-keto acid
Systematic name: 3-methyl-2-oxobutanoate:[dihydrolipoyllysine-residue (2-methylpropanoyl)transferase]-lipoyllysine 2-oxidoreductase (decarboxylating, acceptor-2-methylpropanoylating)
Comments: Contains thiamine diphosphate. It acts not only on 3-methyl-2-oxobutanaoate, but also on 4-methyl-2-oxopentanoate and (S)-3-methyl-2-oxopentanoate, so that it acts on the 2-oxo acids that derive from the action of transaminases on valine, leucine and isoleucine. It is a component of the multienzyme 3-methyl-2-oxobutanoate dehydrogenase complex in which multiple copies of it are bound to a core of molecules of EC 2.3.1.168, dihydrolipoyllysine-residue (2-methylpropanoyl)transferase, which also binds multiple copies of EC 1.8.1.4, dihydrolipoyl dehydrogenase. It does not act on free lipoamide or lipoyllysine, but only on the lipoyllysine residue in EC 2.3.1.168.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9082-72-8
References:
1.  Bowden, J.A. and Connelly, J.L. Branched chain α-keto acid metabolism. II. Evidence for the common identity of α-ketoisocaproic acid and α-keto-β-methyl-valeric acid dehydrogenases. J. Biol. Chem. 243 (1968) 3526–3531. [PMID: 5656388]
2.  Connelly, J.L., Danner, D.J. and Bowden, J.A. Branched chain α-keto acid metabolism. I. Isolation, purification, and partial characterization of bovine liver α-ketoisocaproic:α-keto-β-methylvaleric acid dehydrogenase. J. Biol. Chem. 243 (1968) 1198–1203. [PMID: 5689906]
3.  Danner, D.J., Lemmon, S.K., Beharse, J.C. and Elsas, L.J., II Purification and characterization of branched chain α-ketoacid dehydrogenase from bovine liver mitochondria. J. Biol. Chem. 254 (1979) 5522–5526. [PMID: 447664]
4.  Pettit, F.H., Yeaman, S.J. and Reed, L.J. Purification and characterization of branched chain α-keto acid dehydrogenase complex of bovine kidney. Proc. Natl. Acad. Sci. USA 75 (1978) 4881–4885. [DOI] [PMID: 283398]
5.  Perham, R.N. Swinging arms and swinging domains in multifunctional enzymes: catalytic machines for multistep reactions. Annu. Rev. Biochem. 69 (2000) 961–1004. [DOI] [PMID: 10966480]
[EC 1.2.4.4 created 1972 (EC 1.2.4.3 created 1972, incorporated 1978), modified 2003]
 
 
EC 1.2.7.1     
Accepted name: pyruvate synthase
Reaction: pyruvate + CoA + 2 oxidized ferredoxin = acetyl-CoA + CO2 + 2 reduced ferredoxin + 2 H+
For diagram of the 3-hydroxypropanoate/4-hydroxybutanoate cycle and dicarboxylate/4-hydroxybutanoate cycle in archaea, click here
Other name(s): pyruvate oxidoreductase; pyruvate synthetase; pyruvate:ferredoxin oxidoreductase; pyruvic-ferredoxin oxidoreductase; 2-oxobutyrate synthase; α-ketobutyrate-ferredoxin oxidoreductase; 2-ketobutyrate synthase; α-ketobutyrate synthase; 2-oxobutyrate-ferredoxin oxidoreductase; 2-oxobutanoate:ferredoxin 2-oxidoreductase (CoA-propionylating); 2-oxobutanoate:ferredoxin 2-oxidoreductase (CoA-propanoylating)
Systematic name: pyruvate:ferredoxin 2-oxidoreductase (CoA-acetylating)
Comments: Contains thiamine diphosphate and [4Fe-4S] clusters. The enzyme also decarboxylates 2-oxobutyrate with lower efficiency, but shows no activity with 2-oxoglutarate. This enzyme is a member of the 2-oxoacid oxidoreductases, a family of enzymes that oxidatively decarboxylate different 2-oxoacids to form their CoA derivatives, and are differentiated based on their substrate specificity. For examples of other members of this family, see EC 1.2.7.3, 2-oxoglutarate synthase and EC 1.2.7.7, 3-methyl-2-oxobutanoate dehydrogenase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9082-51-3
References:
1.  Evans, M.C.W. and Buchanan, B.B. Photoreduction of ferredoxin and its use in carbon dioxide fixation by a subcellular system from a photosynthetic bacterium. Proc. Natl. Acad. Sci. USA 53 (1965) 1420–1425. [DOI] [PMID: 5217644]
2.  Gehring, U. and Arnon, D.I. Purification and properties of α-ketoglutarate synthase from a photosynthetic bacterium. J. Biol. Chem. 247 (1972) 6963–6969. [PMID: 4628267]
3.  Uyeda, K. and Rabinowitz, J.C. Pyruvate-ferredoxin oxidoreductase. 3. Purification and properties of the enzyme. J. Biol. Chem. 246 (1971) 3111–3119. [PMID: 5574389]
4.  Uyeda, K. and Rabinowitz, J.C. Pyruvate-ferredoxin oxidoreductase. IV. Studies on the reaction mechanism. J. Biol. Chem. 246 (1971) 3120–3125. [PMID: 4324891]
5.  Charon, M.-H., Volbeda, A., Chabriere, E., Pieulle, L. and Fontecilla-Camps, J.C. Structure and electron transfer mechanism of pyruvate:ferredoxin oxidoreductase. Curr. Opin. Struct. Biol. 9 (1999) 663–669. [DOI] [PMID: 10607667]
[EC 1.2.7.1 created 1972, modified 2003, modified 2013]
 
 
EC 1.2.7.2      
Deleted entry: 2-oxobutyrate synthase. Now included with EC 1.2.7.1, pyruvate synthase.
[EC 1.2.7.2 created 1972, deleted 2013]
 
 
EC 1.2.7.3     
Accepted name: 2-oxoglutarate synthase
Reaction: 2-oxoglutarate + CoA + 2 oxidized ferredoxin = succinyl-CoA + CO2 + 2 reduced ferredoxin + 2 H+
Other name(s): 2-ketoglutarate ferredoxin oxidoreductase; 2-oxoglutarate:ferredoxin oxidoreductase; KGOR; 2-oxoglutarate ferredoxin oxidoreductase; 2-oxoglutarate:ferredoxin 2-oxidoreductase (CoA-succinylating)
Systematic name: 2-oxoglutarate:ferredoxin oxidoreductase (decarboxylating)
Comments: The enzyme contains thiamine diphosphate and two [4Fe-4S] clusters. Highly specific for 2-oxoglutarate. This enzyme is a member of the 2-oxoacid oxidoreductases, a family of enzymes that oxidatively decarboxylate different 2-oxoacids to form their CoA derivatives, and are differentiated based on their substrate specificity. For examples of other members of this family, see EC 1.2.7.1, pyruvate synthase and EC 1.2.7.7, 3-methyl-2-oxobutanoate dehydrogenase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37251-05-1
References:
1.  Buchanan, B.B. and Evans, M.C.W. The synthesis of α-ketoglutarate from succinate and carbon dioxide by a subcellular preparation of a photosynthetic bacterium. Proc. Natl. Acad. Sci. USA 54 (1965) 1212–1218. [DOI] [PMID: 4286833]
2.  Gehring, U. and Arnon, D.I. Purification and properties of α-ketoglutarate synthase from a photosynthetic bacterium. J. Biol. Chem. 247 (1972) 6963–6969. [PMID: 4628267]
3.  Dorner, E. and Boll, M. Properties of 2-oxoglutarate:ferredoxin oxidoreductase from Thauera aromatica and its role in enzymatic reduction of the aromatic ring. J. Bacteriol. 184 (2002) 3975–3983. [DOI] [PMID: 12081970]
4.  Mai, X. and Adams, M.W. Characterization of a fourth type of 2-keto acid-oxidizing enzyme from a hyperthermophilic archaeon: 2-ketoglutarate ferredoxin oxidoreductase from Thermococcus litoralis. J. Bacteriol. 178 (1996) 5890–5896. [DOI] [PMID: 8830683]
5.  Schut, G.J., Menon, A.L. and Adams, M.W.W. 2-Keto acid oxidoreductases from Pyrococcus furiosus and Thermococcus litoralis. Methods Enzymol. 331 (2001) 144–158. [DOI] [PMID: 11265457]
[EC 1.2.7.3 created 1972, modified 2005]
 
 
EC 1.2.7.7     
Accepted name: 3-methyl-2-oxobutanoate dehydrogenase (ferredoxin)
Reaction: 3-methyl-2-oxobutanoate + CoA + 2 oxidized ferredoxin = S-(2-methylpropanoyl)-CoA + CO2 + 2 reduced ferredoxin + H+
Other name(s): 2-ketoisovalerate ferredoxin reductase; 3-methyl-2-oxobutanoate synthase (ferredoxin); VOR; branched-chain ketoacid ferredoxin reductase; branched-chain oxo acid ferredoxin reductase; keto-valine-ferredoxin oxidoreductase; ketoisovalerate ferredoxin reductase; 2-oxoisovalerate ferredoxin reductase
Systematic name: 3-methyl-2-oxobutanoate:ferredoxin oxidoreductase (decarboxylating; CoA-2-methylpropanoylating)
Comments: The enzyme is CoA-dependent and contains thiamine diphosphate and iron-sulfur clusters. Preferentially utilizes 2-oxo-acid derivatives of branched chain amino acids, e.g. 3-methyl-2-oxopentanoate, 4-methyl-2-oxo-pentanoate, and 2-oxobutanoate. This enzyme is a member of the 2-oxoacid oxidoreductases, a family of enzymes that reversibly catalyse the oxidative decarboxylation of different 2-oxoacids to form their CoA derivatives, and are differentiated based on their substrate specificity. For examples of other members of this family, see EC 1.2.7.1, pyruvate synthase, and EC 1.2.7.3, 2-oxoglutarate synthase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Buchanan, B.B. Role of ferredoxin in the synthesis of α-ketobutyrate from propionyl coenzyme A and carbon dioxide by enzymes from photosynthetic and nonphotosynthetic bacteria. J. Biol. Chem. 244 (1969) 4218–4223. [PMID: 5800441]
2.  Heider, J., Mai, X.H. and Adams, M.W.W. Characterization of 2-ketoisovalerate ferredoxin oxidoreductase, a new and reversible coenzyme A-dependent enzyme involved in peptide fermentation by hyperthermophilic archaea. J. Bacteriol. 178 (1996) 780–787. [DOI] [PMID: 8550513]
3.  Tersteegen, A., Linder, D., Thauer, R.K. and Hedderich, R. Structures and functions of four anabolic 2-oxoacid oxidoreductases in Methanobacterium thermoautotrophicum. Eur. J. Biochem. 244 (1997) 862–868. [DOI] [PMID: 9108258]
4.  Schut, G.J., Menon, A.L. and Adams, M.W.W. 2-Keto acid oxidoreductases from Pyrococcus furiosus and Thermococcus litoralis. Methods Enzymol. 331 (2001) 144–158. [DOI] [PMID: 11265457]
[EC 1.2.7.7 created 2003]
 
 
EC 1.2.7.8     
Accepted name: indolepyruvate ferredoxin oxidoreductase
Reaction: (indol-3-yl)pyruvate + CoA + 2 oxidized ferredoxin = S-2-(indol-3-yl)acetyl-CoA + CO2 + 2 reduced ferredoxin + H+
Other name(s): 3-(indol-3-yl)pyruvate synthase (ferredoxin); IOR
Systematic name: 3-(indol-3-yl)pyruvate:ferredoxin oxidoreductase (decarboxylating, CoA-indole-acetylating)
Comments: Contains thiamine diphosphate and [4Fe-4S] clusters. Preferentially utilizes the transaminated forms of aromatic amino acids and can use phenylpyruvate and p-hydroxyphenylpyruvate as substrates. This enzyme, which is found in archaea, is a member of the 2-oxoacid oxidoreductases, a family of enzymes that oxidatively decarboxylate different 2-oxoacids to form their CoA derivatives, and are differentiated based on their substrate specificity. For examples of other members of this family, see EC 1.2.7.3, 2-oxoglutarate synthase and EC 1.2.7.7, 3-methyl-2-oxobutanoate dehydrogenase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 158886-06-7
References:
1.  Mai, X.H. and Adams, M.W.W. Indolepyruvate ferredoxin oxidoreductase from the hyperthermophilic archaeon Pyrococcus furiosus - a new enzyme involved in peptide fermentation. J. Biol. Chem. 269 (1994) 16726–16732. [PMID: 8206994]
2.  Siddiqui, M.A., Fujiwara, S. and Imanaka, T. Indolepyruvate ferredoxin oxidoreductase from Pyrococcus sp. K0d1 possesses a mosaic: Structure showing features of various oxidoreductases. Mol. Gen. Genet. 254 (1997) 433–439. [PMID: 9180697]
3.  Tersteegen, A., Linder, D., Thauer, R.K. and Hedderich, R. Structures and functions of four anabolic 2-oxoacid oxidoreductases in Methanobacterium thermoautotrophicum. Eur. J. Biochem. 244 (1997) 862–868. [DOI] [PMID: 9108258]
4.  Schut, G.J., Menon, A.L. and Adams, M.W.W. 2-Keto acid oxidoreductases from Pyrococcus furiosus and Thermococcus litoralis. Methods Enzymol. 331 (2001) 144–158. [DOI] [PMID: 11265457]
[EC 1.2.7.8 created 2003]
 
 
EC 1.2.7.11     
Accepted name: 2-oxoacid oxidoreductase (ferredoxin)
Reaction: a 2-oxocarboxylate + CoA + 2 oxidized ferredoxin = an acyl-CoA + CO2 + 2 reduced ferredoxin + 2 H+
Other name(s): OFOR
Systematic name: 2-oxocarboxylate:ferredoxin 2-oxidoreductase (decarboxylating, CoA-acylating)
Comments: Contains thiamine diphosphate and [4Fe-4S] clusters [2]. This enzyme is a member of the 2-oxoacid oxidoreductases, a family of enzymes that oxidatively decarboxylate different 2-oxoacids to form their CoA derivatives, and are differentiated based on their substrate specificity. For example, see EC 1.2.7.3, 2-oxoglutarate synthase and EC 1.2.7.7, 3-methyl-2-oxobutanoate dehydrogenase (ferredoxin).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Kerscher, L. and Oesterhelt, D. Purification and properties of two 2-oxoacid:ferredoxin oxidoreductases from Halobacterium halobium. Eur. J. Biochem. 116 (1981) 587–594. [DOI] [PMID: 6266826]
2.  Zhang, Q., Iwasaki, T., Wakagi, T. and Oshima, T. 2-oxoacid:ferredoxin oxidoreductase from the thermoacidophilic archaeon, Sulfolobus sp. strain 7. J. Biochem. 120 (1996) 587–599. [PMID: 8902625]
3.  Fukuda, E., Kino, H., Matsuzawa, H. and Wakagi, T. Role of a highly conserved YPITP motif in 2-oxoacid:ferredoxin oxidoreductase: heterologous expression of the gene from Sulfolobus sp.strain 7, and characterization of the recombinant and variant enzymes. Eur. J. Biochem. 268 (2001) 5639–5646. [DOI] [PMID: 11683888]
4.  Fukuda, E. and Wakagi, T. Substrate recognition by 2-oxoacid:ferredoxin oxidoreductase from Sulfolobus sp. strain 7. Biochim. Biophys. Acta 1597 (2002) 74–80. [DOI] [PMID: 12009405]
5.  Nishizawa, Y., Yabuki, T., Fukuda, E. and Wakagi, T. Gene expression and characterization of two 2-oxoacid:ferredoxin oxidoreductases from Aeropyrum pernix K1. FEBS Lett. 579 (2005) 2319–2322. [DOI] [PMID: 15848165]
6.  Park, Y.J., Yoo, C.B., Choi, S.Y. and Lee, H.B. Purifications and characterizations of a ferredoxin and its related 2-oxoacid:ferredoxin oxidoreductase from the hyperthermophilic archaeon, Sulfolobus solfataricus P1. J. Biochem. Mol. Biol. 39 (2006) 46–54. [PMID: 16466637]
[EC 1.2.7.11 created 2013]
 
 
EC 1.4.1.8     
Accepted name: valine dehydrogenase (NADP+)
Reaction: L-valine + H2O + NADP+ = 3-methyl-2-oxobutanoate + NH3 + NADPH + H+
Other name(s): valine dehydrogenase (nicotinanide adenine dinucleotide phosphate); valine dehydrogenase (NADP)
Systematic name: L-valine:NADP+ oxidoreductase (deaminating)
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37255-39-3
References:
1.  Kagan, Z.S., Kretovich, V.L. and Polyakov, V.A. Biosynthesis of valine by reductive amination of its keto analogue in plants. Enzymologia 30 (1966) 343–366. [PMID: 6005410]
2.  Kagan, Z.S., Polyakov, V.A. and Kretovich, V.L. Soluble valine dehydrogenase from roots of plant seedings. Biochemistry (Mosc.) 33 (1968) 74–84. [PMID: 4385962]
3.  Kagan, Z.S., Polyakov, V.A. and Kretovich, V.L. Purification and properties of valine dehydrogenase. Biochemistry (Mosc.) 34 (1969) 47–51. [PMID: 4389825]
[EC 1.4.1.8 created 1972]
 
 
EC 1.4.1.23     
Accepted name: valine dehydrogenase (NAD+)
Reaction: L-valine + H2O + NAD+ = 3-methyl-2-oxobutanoate + NH3 + NADH + H+
Systematic name: L-valine:NAD+ oxidoreductase (deaminating)
Comments: The enzyme from Streptomyces spp. has no activity with NADP+ [cf. EC 1.4.1.8, valine dehydrogenase (NADP+)].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Vancurová, I., Vancura, A., Volc, J., Neuzil, J., Flieger, M., Basarová, G. and Behal, V. Isolation and characterization of valine dehydrogenase from Streptomyces aureofaciens. J. Bacteriol. 170 (1988) 5192–5196. [DOI] [PMID: 3182727]
2.  Navarrete, R.M., Vara, J.A. and Hutchinson, C.R. Purification of an inducible L-valine dehydrogenase of Streptomyces coelicolor A3(2). J. Gen. Microbiol. 136 (1990) 273–281. [DOI] [PMID: 2324704]
[EC 1.4.1.23 created 2012]
 
 
EC 1.5.1.16     
Accepted name: D-lysopine dehydrogenase
Reaction: N2-(D-1-carboxyethyl)-L-lysine + NADP+ + H2O = L-lysine + pyruvate + NADPH + H+
Other name(s): D-lysopine synthase; lysopine dehydrogenase; D(+)-lysopine dehydrogenase; 2-N-(D-1-carboxyethyl)-L-lysine:NADP+ oxidoreductase (L-lysine-forming)
Systematic name: N2-(D-1-carboxyethyl)-L-lysine:NADP+ oxidoreductase (L-lysine-forming)
Comments: In the reverse reaction, a number of L-amino acids can act instead of L-lysine, and 2-oxobutanoate and, to a lesser extent, glyoxylate can act instead of pyruvate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 65187-41-9
References:
1.  Otten, L.A.B.M., Vreugdenhil, D. and Schilperoort, R.A. Properties of D(+)-lysopine dehydrogenase from crown gall tumour tissue. Biochim. Biophys. Acta 485 (1977) 268–277. [DOI] [PMID: 21695]
[EC 1.5.1.16 created 1978]
 
 
EC 1.5.1.23     
Accepted name: tauropine dehydrogenase
Reaction: tauropine + NAD+ + H2O = taurine + pyruvate + NADH + H+
Glossary: tauropine = N2-(D-1-carboxyethyl)-2-aminoethanesulfonate
Other name(s): 2-N-(D-1-carboxyethyl)taurine:NAD+ oxidoreductase (taurine-forming)
Systematic name: N2-(D-1-carboxyethyl)taurine:NAD+ oxidoreductase (taurine-forming)
Comments: In the reverse reaction, alanine can act instead of taurine, but more slowly, and 2-oxobutanoate and 2-oxopentanoate can act instead of pyruvate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 104645-74-1
References:
1.  Gäde, G. Purification and properties of tauropine dehydrogenase from the shell adductor muscle of the ormer, Haliotis lamellosa. Eur. J. Biochem. 160 (1986) 311–318. [DOI] [PMID: 3769931]
[EC 1.5.1.23 created 1989]
 
 
EC 1.8.1.4     
Accepted name: dihydrolipoyl dehydrogenase
Reaction: protein N6-(dihydrolipoyl)lysine + NAD+ = protein N6-(lipoyl)lysine + NADH + H+
For diagram of glycine cleavage system, click here, for diagram of the citric acid cycle, click here and for diagram of oxo-acid dehydrogenase complexes, click here
Glossary: dihydrolipoyl = (6R)-6,8-disulfanyloctanoyl
For structure of dihydrolipoyl, click here
Other name(s): LDP-Glc; LDP-Val; dehydrolipoate dehydrogenase; diaphorase; dihydrolipoamide dehydrogenase; dihydrolipoamide:NAD+ oxidoreductase; dihydrolipoic dehydrogenase; dihydrothioctic dehydrogenase; lipoamide dehydrogenase (NADH); lipoamide oxidoreductase (NADH); lipoamide reductase; lipoamide reductase (NADH); lipoate dehydrogenase; lipoic acid dehydrogenase; lipoyl dehydrogenase; protein-6-N-(dihydrolipoyl)lysine:NAD+ oxidoreductase
Systematic name: protein-N6-(dihydrolipoyl)lysine:NAD+ oxidoreductase
Comments: A flavoprotein (FAD). A component of the multienzyme 2-oxo-acid dehydrogenase complexes. In the pyruvate dehydrogenase complex, it binds to the core of EC 2.3.1.12, dihydrolipoyllysine-residue acetyltransferase, and catalyses oxidation of its dihydrolipoyl groups. It plays a similar role in the oxoglutarate and 3-methyl-2-oxobutanoate dehydrogenase complexes. Another substrate is the dihydrolipoyl group in the H-protein of the glycine-cleavage system (click here for diagram), in which it acts, together with EC 1.4.4.2, glycine dehydrogenase (decarboxylating), and EC 2.1.2.10, aminomethyltransferase, to break down glycine. It can also use free dihydrolipoate, dihydrolipoamide or dihydrolipoyllysine as substrate. This enzyme was first shown to catalyse the oxidation of NADH by methylene blue; this activity was called diaphorase. The glycine cleavage system is composed of four components that only loosely associate: the P protein (EC 1.4.4.2), the T protein (EC 2.1.2.10), the L protein (EC 1.8.1.4) and the lipoyl-bearing H protein [6].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9001-18-7
References:
1.  Massey, V. Lipoyl dehydrogenase. In: Boyer, P.D., Lardy, H. and Myrbäck, K. (Ed.), The Enzymes, 2nd edn, vol. 7, Academic Press, New York, 1963, pp. 275–306.
2.  Massey, V., Gibson, Q.H. and Veeger, C. Intermediates in the catalytic action of lipoyl dehydrogenase (diaphorase). Biochem. J. 77 (1960) 341–351. [PMID: 13767908]
3.  Savage, N. Preparation and properties of highly purified diaphorase. Biochem. J. 67 (1957) 146–155. [PMID: 13471525]
4.  Straub, F.B. Isolation and properties of a flavoprotein from heart muscle tissue. Biochem. J. 33 (1939) 787–792. [PMID: 16746974]
5.  Perham, R.N. Swinging arms and swinging domains in multifunctional enzymes: catalytic machines for multistep reactions. Annu. Rev. Biochem. 69 (2000) 961–1004. [DOI] [PMID: 10966480]
6.  Nesbitt, N.M., Baleanu-Gogonea, C., Cicchillo, R.M., Goodson, K., Iwig, D.F., Broadwater, J.A., Haas, J.A., Fox, B.G. and Booker, S.J. Expression, purification, and physical characterization of Escherichia coli lipoyl(octanoyl)transferase. Protein Expr. Purif. 39 (2005) 269–282. [DOI] [PMID: 15642479]
[EC 1.8.1.4 created 1961 as EC 1.6.4.3, modified 1976, transferred 1983 to EC 1.8.1.4, modified 2003, modified 2006]
 
 
EC 1.13.11.54     
Accepted name: acireductone dioxygenase [iron(II)-requiring]
Reaction: 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + O2 = 4-(methylsulfanyl)-2-oxobutanoate + formate
For diagram of methionine salvage, click here and for diagram of reaction, click here
Glossary: acireductone = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one
Other name(s): ARD′; 2-hydroxy-3-keto-5-thiomethylpent-1-ene dioxygenase (ambiguous); acireductone dioxygenase (ambiguous); E-2′; E-3 dioxygenase; 1,2-dihydroxy-5-(methylthio)pent-1-en-3-one:oxygen oxidoreductase (formate-forming)
Systematic name: 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one:oxygen oxidoreductase (formate-forming)
Comments: Requires iron(II). If Ni2+ is bound instead of iron(II), the reaction catalysed by EC 1.13.11.53, acireductone dioxygenase (Ni2+-requiring), occurs instead. The enzyme from the bacterium Klebsiella oxytoca (formerly Klebsiella pneumoniae) ATCC strain 8724 is involved in the methionine salvage pathway.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Wray, J.W. and Abeles, R.H. A bacterial enzyme that catalyzes formation of carbon monoxide. J. Biol. Chem. 268 (1993) 21466–21469. [PMID: 8407993]
2.  Wray, J.W. and Abeles, R.H. The methionine salvage pathway in Klebsiella pneumoniae and rat liver. Identification and characterization of two novel dioxygenases. J. Biol. Chem. 270 (1995) 3147–3153. [DOI] [PMID: 7852397]
3.  Furfine, E.S. and Abeles, R.H. Intermediates in the conversion of 5′-S-methylthioadenosine to methionine in Klebsiella pneumoniae. J. Biol. Chem. 263 (1988) 9598–9606. [PMID: 2838472]
4.  Dai, Y., Wensink, P.C. and Abeles, R.H. One protein, two enzymes. J. Biol. Chem. 274 (1999) 1193–1195. [DOI] [PMID: 9880484]
5.  Mo, H., Dai, Y., Pochapsky, S.S. and Pochapsky, T.C. 1H, 13C and 15N NMR assignments for a carbon monoxide generating metalloenzyme from Klebsiella pneumoniae. J. Biomol. NMR 14 (1999) 287–288. [PMID: 10481280]
6.  Dai, Y., Pochapsky, T.C. and Abeles, R.H. Mechanistic studies of two dioxygenases in the methionine salvage pathway of Klebsiella pneumoniae. Biochemistry 40 (2001) 6379–6387. [DOI] [PMID: 11371200]
7.  Al-Mjeni, F., Ju, T., Pochapsky, T.C. and Maroney, M.J. XAS investigation of the structure and function of Ni in acireductone dioxygenase. Biochemistry 41 (2002) 6761–6769. [DOI] [PMID: 12022880]
8.  Pochapsky, T.C., Pochapsky, S.S., Ju, T., Mo, H., Al-Mjeni, F. and Maroney, M.J. Modeling and experiment yields the structure of acireductone dioxygenase from Klebsiella pneumoniae. Nat. Struct. Biol. 9 (2002) 966–972. [DOI] [PMID: 12402029]
[EC 1.13.11.54 created 2006]
 
 
EC 2.1.1.47     
Accepted name: indolepyruvate C-methyltransferase
Reaction: S-adenosyl-L-methionine + (indol-3-yl)pyruvate = S-adenosyl-L-homocysteine + (R)-3-(indol-3-yl)-2-oxobutanoate
Other name(s): ind1 (gene name); indolepyruvate methyltransferase; indolepyruvate 3-methyltransferase; indolepyruvic acid methyltransferase; S-adenosyl-L-methionine:indolepyruvate C-methyltransferase
Systematic name: S-adenosyl-L-methionine:(indol-3-yl)pyruvate C3-methyltransferase
Comments: The enzyme, characterized from the bacterium Streptomyces griseus, is involved in the biosynthesis of the antibacterial drug indolmycin.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 54576-88-4
References:
1.  Hornemann, U., Speedie, M.K., Hurley, L.H. and Floss, H.G. Demonstration of a C-methylating enzyme in cell free extracts of indolmycin-producing Streptomyces griseus. Biochem. Biophys. Res. Commun. 39 (1970) 594–599. [DOI] [PMID: 5490210]
2.  Hornemann, U., Hurley, L.H., Speedie, M.K. and Floss, H.G. The biosynthesis of indolmycin. J. Am. Chem. Soc. 93 (1971) 3028–3035. [PMID: 5095271]
3.  Speedie, M.K., Hornemann, U. and Floss, H.G. Isolation and characterization of tryptophan transaminase and indolepyruvate C-methyltransferase. Enzymes involved in indolmycin biosynthesis in Streptomyces griseus. J. Biol. Chem. 250 (1975) 7819–7825. [PMID: 809439]
4.  Du, Y.L., Alkhalaf, L.M. and Ryan, K.S. In vitro reconstitution of indolmycin biosynthesis reveals the molecular basis of oxazolinone assembly. Proc. Natl. Acad. Sci. USA 112 (2015) 2717–2722. [DOI] [PMID: 25730866]
[EC 2.1.1.47 created 1976, modified 2016]
 
 
EC 2.1.2.11     
Accepted name: 3-methyl-2-oxobutanoate hydroxymethyltransferase
Reaction: 5,10-methylenetetrahydrofolate + 3-methyl-2-oxobutanoate + H2O = tetrahydrofolate + 2-dehydropantoate
For diagram of the early stages of CoA biosynthesis, click here
Other name(s): α-ketoisovalerate hydroxymethyltransferase; dehydropantoate hydroxymethyltransferase; ketopantoate hydroxymethyltransferase; oxopantoate hydroxymethyltransferase; 5,10-methylene tetrahydrofolate:α-ketoisovalerate hydroxymethyltransferase
Systematic name: 5,10-methylenetetrahydrofolate:3-methyl-2-oxobutanoate hydroxymethyltransferase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 56093-17-5
References:
1.  Powers, S.G. and Snell, E.E. Ketopantoate hydroxymethyltransferase. II. Physical, catalytic, and regulatory properties. J. Biol. Chem. 251 (1976) 3786–3793. [PMID: 6463]
2.  Teller, J.H., Powers, S.G. and Snell, E.E. Ketopantoate hydroxymethyltransferase. I. Purification and role in pantothenate biosynthesis. J. Biol. Chem. 251 (1976) 3780–3785. [PMID: 776976]
[EC 2.1.2.11 created 1982]
 
 
EC 2.2.1.6     
Accepted name: acetolactate synthase
Reaction: 2 pyruvate = 2-acetolactate + CO2
For diagram of reaction mechanism, click here
Glossary: thiamine diphosphate = 3-[(4-amino-2-methylpyrimidin-5-yl)methyl]-5-(2-diphosphoethyl)-4-methyl-1,3-thiazolium
Other name(s): α-acetohydroxy acid synthetase; α-acetohydroxyacid synthase; α-acetolactate synthase; α-acetolactate synthetase; acetohydroxy acid synthetase; acetohydroxyacid synthase; acetolactate pyruvate-lyase (carboxylating); acetolactic synthetase
Systematic name: pyruvate:pyruvate acetaldehydetransferase (decarboxylating)
Comments: This enzyme requires thiamine diphosphate. The reaction shown is in the pathway of biosynthesis of valine; the enzyme can also transfer the acetaldehyde from pyruvate to 2-oxobutanoate, forming 2-ethyl-2-hydroxy-3-oxobutanoate, also known as 2-aceto-2-hydroxybutanoate, a reaction in the biosynthesis of isoleucine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9027-45-6
References:
1.  Bauerle, R.H., Freundlich, M., Størmer, F.C. and Umbarger, H.E. Control of isoleucine, valine and leucine biosynthesis. II. Endproduct inhibition by valine of acetohydroxy acid synthetase in Salmonella typhimurium. Biochim. Biophys. Acta 92 (1964) 142–149. [PMID: 14243762]
2.  Huseby, N.E., Christensen, T.B., Olsen, B.R. and Størmer, F.C. The pH 6 acetolactate-forming enzyme from Aerobacter aerogenes. Subunit structure. Eur. J. Biochem. 20 (1971) 209–214. [DOI] [PMID: 5560406]
3.  Størmer, F.C., Solberg, Y. and Hovig, T. The pH 6 acetolactate-forming enzyme from Aerobacter aerogenes. Molecular properties. Eur. J. Biochem. 10 (1969) 251–260. [DOI] [PMID: 5823101]
4.  Barak, Z., Chipman, D.M. and Gollop, N. Physiological implications of the specificity of acetohydroxy acid synthase isozymes of enteric bacteria. J. Bacteriol. 169 (1987) 3750–3756. [DOI] [PMID: 3301814]
[EC 2.2.1.6 created 1972 as EC 4.1.3.18, transferred 2002 to EC 2.2.1.6]
 
 
EC 2.3.1.168     
Accepted name: dihydrolipoyllysine-residue (2-methylpropanoyl)transferase
Reaction: 2-methylpropanoyl-CoA + enzyme N6-(dihydrolipoyl)lysine = CoA + enzyme N6-(S-[2-methylpropanoyl]dihydrolipoyl)lysine
For diagram of oxo-acid-dehydrogenase complexes, click here
Glossary: dihydrolipoyl group
Other name(s): dihydrolipoyl transacylase; enzyme-dihydrolipoyllysine:2-methylpropanoyl-CoA S-(2-methylpropanoyl)transferase; 2-methylpropanoyl-CoA:enzyme-6-N-(dihydrolipoyl)lysine S-(2-methylpropanoyl)transferase
Systematic name: 2-methylpropanoyl-CoA:enzyme-N6-(dihydrolipoyl)lysine S-(2-methylpropanoyl)transferase
Comments: A multimer (24-mer) of this enzyme forms the core of the multienzyme 3-methyl-2-oxobutanoate dehydrogenase complex, and binds tightly both EC 1.2.4.4, 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring) and EC 1.8.1.4, dihydrolipoyl dehydrogenase. The lipoyl group of this enzyme is reductively 2-methylpropanoylated by EC 1.2.4.4, and the only observed direction catalysed by EC 2.3.1.168 is that where this 2-methylpropanoyl is passed to coenzyme A. In addition to the 2-methylpropanoyl group, formed when EC 1.2.4.4 acts on the oxoacid that corresponds with valine, this enzyme also transfers the 3-methylbutanoyl and S-2-methylbutanoyl groups, donated to it when EC 1.2.4.4 acts on the oxo acids corresponding with leucine and isoleucine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 102784-26-9
References:
1.  Massey, L.K., Sokatch, J.R. and Conrad, R.S. Branched-chain amino acid catabolism in bacteria. Bacteriol. Rev. 40 (1976) 42–54. [PMID: 773366]
2.  Chuang, D.T., Hu, C.C., Ku, L.S., Niu, W.L., Myers, D.E. and Cox, R.P. Catalytic and structural properties of the dihydrolipoyl transacylase component of bovine branched-chain α-keto acid dehydrogenase. J. Biol. Chem. 259 (1984) 9277–9284. [PMID: 6746648]
3.  Wynn, R.M., Davie, J.R., Zhi, W., Cox, R.P. and Chuang, D.T. In vitro reconstitution of the 24-meric E2 inner core of bovine mitochondrial branched-chain α-keto acid dehydrogenase complex: requirement for chaperonins GroEL and GroES. Biochemistry 33 (1994) 8962–8968. [PMID: 7913832]
4.  Perham, R.N. Swinging arms and swinging domains in multifunctional enzymes: catalytic machines for multistep reactions. Annu. Rev. Biochem. 69 (2000) 961–1004. [DOI] [PMID: 10966480]
[EC 2.3.1.168 created 2003]
 
 
EC 2.3.1.182      
Transferred entry: (R)-citramalate synthase. Now classified as EC 2.3.3.21, (R)-citramalate synthase.
[EC 2.3.1.182 created 2007, deleted 2021]
 
 
EC 2.3.3.6     
Accepted name: 2-ethylmalate synthase
Reaction: acetyl-CoA + H2O + 2-oxobutanoate = (R)-2-ethylmalate + CoA
For diagram of reaction, click here
Other name(s): (R)-2-ethylmalate 2-oxobutanoyl-lyase (CoA-acetylating); 2-ethylmalate-3-hydroxybutanedioate synthase; propylmalate synthase; propylmalic synthase
Systematic name: acetyl-CoA:2-oxobutanoate C-acetyltransferase (thioester-hydrolysing, carboxymethyl-forming)
Comments: Also acts on (R)-2-(n-propyl)-malate. Formerly wrongly included with EC 2.3.3.7 3-ethylmalate synthase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9024-01-5
References:
1.  Strassman, M. and Ceci, L.N. A study of acetyl-CoA condensation with α-keto acids. Arch. Biochem. Biophys. 119 (1967) 420–428. [PMID: 6052435]
[EC 2.3.3.6 created 1983 as EC 4.1.3.33, transferred 2002 to EC 2.3.3.6]
 
 
EC 2.3.3.13     
Accepted name: 2-isopropylmalate synthase
Reaction: acetyl-CoA + 3-methyl-2-oxobutanoate + H2O = (2S)-2-isopropylmalate + CoA
For diagram of leucine-biosynthesis pathway, click here
Other name(s): 3-carboxy-3-hydroxy-4-methylpentanoate 3-methyl-2-oxobutanoate-lyase (CoA-acetylating); α-isopropylmalate synthetase; α-isopropylmalate synthase; α-isopropylmalic synthetase; isopropylmalate synthase; isopropylmalate synthetase
Systematic name: acetyl-CoA:3-methyl-2-oxobutanoate C-acetyltransferase (thioester-hydrolysing, carboxymethyl-forming)
Comments: Requires K+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9030-98-2
References:
1.  Kohlhaw, G., Leary, T.R. and Umbarger, H.E. α-Isopropylmalate synthase from Salmonella typhimurium. Purification and properties. J. Biol. Chem. 244 (1969) 2218–2225. [PMID: 4976555]
2.  Webster, R.E. and Gross, S.R. The α-isopropylmalate synthetase of Neurospora. I. The kinetics and end product control of α-isopropylmalate synthetase function. Biochemistry 4 (1965) 2309–2327.
3.  Cole, F.E., Kalyanpur, M. G. and Stevens, C. M. Absolute configuration of α-isopropylmalate and the mechanism of its conversion to β-isopropylmalate in the biosynthesis of leucine. Biochemistry 12 (1973) 3346–3350. [PMID: 4270046]
[EC 2.3.3.13 created 1972 as EC 4.1.3.12, transferred 2002 to EC 2.3.3.13]
 
 
EC 2.3.3.21     
Accepted name: (R)-citramalate synthase
Reaction: acetyl-CoA + pyruvate + H2O = CoA + (2R)-2-hydroxy-2-methylbutanedioate
Glossary: (2R)-2-hydroxy-2-methylbutanedioate = (2R)-2-methylmalate = (–)-citramalate
3-methyl-2-oxobutanoate = α-ketoisovalerate
2-oxobutanoate = α-ketobutyrate
4-methyl-2-oxopentanoate = α-ketoisocaproate
2-oxohexanoate = α-ketopimelate
2-oxoglutarate = α-ketoglutarate
Other name(s): CimA
Comments: One of the enzymes involved in a pyruvate-derived pathway for isoleucine biosynthesis that is found in some bacterial and archaeal species [1,2]. The enzyme can be inhibited by isoleucine, the end-product of the pathway, but not by leucine [2]. The enzyme is highly specific for pyruvate as substrate, as the 2-oxo acids 3-methyl-2-oxobutanoate, 2-oxobutanoate, 4-methyl-2-oxopentanoate, 2-oxohexanoate and 2-oxoglutarate cannot act as substrate [1,2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Howell, D.M., Xu, H. and White, R.H. (R)-citramalate synthase in methanogenic archaea. J. Bacteriol. 181 (1999) 331–333. [DOI] [PMID: 9864346]
2.  Xu, H., Zhang, Y., Guo, X., Ren, S., Staempfli, A.A., Chiao, J., Jiang, W. and Zhao, G. Isoleucine biosynthesis in Leptospira interrogans serotype 1ai strain 56601 proceeds via a threonine-independent pathway. J. Bacteriol. 186 (2004) 5400–5409. [DOI] [PMID: 15292141]
[EC 2.3.3.21 created 2007 as EC 2.3.1.182, transferred 2021 to EC 2.3.3.21]
 
 
EC 2.5.1.48     
Accepted name: cystathionine γ-synthase
Reaction: O4-succinyl-L-homoserine + L-cysteine = L-cystathionine + succinate
For diagram of reaction, click here
Other name(s): O-succinyl-L-homoserine succinate-lyase (adding cysteine); O-succinylhomoserine (thiol)-lyase; homoserine O-transsuccinylase (ambiguous); O-succinylhomoserine synthase; O-succinylhomoserine synthetase; cystathionine synthase; cystathionine synthetase; homoserine transsuccinylase (ambiguous); 4-O-succinyl-L-homoserine:L-cysteine S-(3-amino-3-carboxypropyl)transferase
Systematic name: O4-succinyl-L-homoserine:L-cysteine S-(3-amino-3-carboxypropyl)transferase
Comments: A pyridoxal-phosphate protein. Also reacts with hydrogen sulfide and methanethiol as replacing agents, producing homocysteine and methionine, respectively. In the absence of thiol, can also catalyse β,γ-elimination to form 2-oxobutanoate, succinate and ammonia.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9030-70-0
References:
1.  Flavin, M. and Slaughter, C. Enzymatic synthesis of homocysteine or methionine directly from O-succinyl-homoserine. Biochim. Biophys. Acta 132 (1967) 400–405. [DOI] [PMID: 5340123]
2.  Kaplan, M.M. and Flavin, M. Cystathionine γ-synthetase of Salmonella. Catalytic properties of a new enzyme in bacterial methionine biosynthesis. J. Biol. Chem. 241 (1966) 4463–4471. [PMID: 5922970]
3.  Wiebers, J.L. and Garner, H.R. Homocysteine and cysteine synthetases of Neurospora crassa. Purification, properties, and feedback control of activity. J. Biol. Chem. 242 (1967) 12–23. [PMID: 6016326]
4.  Wiebers, J.L. and Garner, H.R. Acyl derivatives of homoserine as substrates for homocysteine synthesis in Neurospora crassa, yeast, and Escherichia coli. J. Biol. Chem. 242 (1967) 5644–5649. [PMID: 12325384]
5.  Clausen, T., Huber, R., Prade, L., Wahl, M.C. and Messerschmidt, A. Crystal structure of Escherichia coli cystathionine γ-synthase at 1.5 Å resolution. EMBO J. 17 (1998) 6827–6838. [DOI] [PMID: 9843488]
6.  Ravanel, S., Gakiere, B., Job, D. and Douce, R. Cystathionine γ-synthase from Arabidopsis thaliana: purification and biochemical characterization of the recombinant enzyme overexpressed in Escherichia coli. Biochem. J. 331 (1998) 639–648. [PMID: 9531508]
[EC 2.5.1.48 created 1972 as EC 4.2.99.9, transferred 2002 to EC 2.5.1.48]
 
 
EC 2.6.1.32     
Accepted name: valine—3-methyl-2-oxovalerate transaminase
Reaction: L-valine + (S)-3-methyl-2-oxopentanoate = 3-methyl-2-oxobutanoate + L-isoleucine
For diagram of EC 2.6.1, click here
Other name(s): valine—isoleucine transaminase; valine-3-methyl-2-oxovalerate aminotransferase; alanine-valine transaminase; valine-2-keto-methylvalerate aminotransferase; valine-isoleucine aminotransferase
Systematic name: L-valine:(S)-3-methyl-2-oxopentanoate aminotransferase
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9023-14-7
References:
1.  Kagan, Z.S., Dronov, A.S. and Kretovich, V.L. [Some properties of valine-isoleucine- and valine-glutamate-aminotransferases of pea sprouts.] Dokl. Akad. Nauk S.S.S.R. 179 (1968) 1236–1239. (in Russian)
[EC 2.6.1.32 created 1972, modified 1976]
 
 
EC 2.6.1.41     
Accepted name: D-methionine—pyruvate transaminase
Reaction: D-methionine + pyruvate = 4-(methylsulfanyl)-2-oxobutanoate + L-alanine
Other name(s): D-methionine transaminase; D-methionine aminotransferase
Systematic name: D-methionine:pyruvate aminotransferase
Comments: Oxaloacetate can replace pyruvate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37277-93-3
References:
1.  Mapson, L.W., March, J.F. and Wardale, D.A. Biosynthesis of ethylene. 4-Methylmercapto-2-oxobutyric acid: an intermediate in the formation from methionine. Biochem. J. 115 (1969) 653–661. [PMID: 5357015]
[EC 2.6.1.41 created 1972, modified 1982]
 
 
EC 2.6.1.44     
Accepted name: alanine—glyoxylate transaminase
Reaction: L-alanine + glyoxylate = pyruvate + glycine
For diagram of reaction, click here and for mechanism, click here
Other name(s): AGT; alanine-glyoxylate aminotransferase; alanine-glyoxylic aminotransferase; L-alanine-glycine transaminase
Systematic name: L-alanine:glyoxylate aminotransferase
Comments: A pyridoxal-phosphate protein. With one component of the animal enzyme, 2-oxobutanoate can replace glyoxylate. A second component also catalyses the reaction of EC 2.6.1.51 serine—pyruvate transaminase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9015-67-2
References:
1.  Noguchi, T., Okuno, E., Takada, Y., Minatogawa, Y., Okai, K. and Kido, R. Characteristics of hepatic alanine-glyoxylate aminotransferase in different mammalian species. Biochem. J. 169 (1978) 113–122. [PMID: 629740]
2.  Okuno, E., Minatogawa, Y. and Kido, R. Co-purification of alanine-glyoxylate aminotransferase with 2-aminobutyrate aminotransferase in rat kidney. Biochim. Biophys. Acta 715 (1982) 97–104. [DOI] [PMID: 6803844]
3.  Thompson, J.S. and Richardson, K.E. Isolation and characterization of an L-alanine: glyoxylate aminotransferase from human liver. J. Biol. Chem. 242 (1967) 3614–3619. [PMID: 6038488]
[EC 2.6.1.44 created 1972, modified 1982]
 
 
EC 2.6.1.62     
Accepted name: adenosylmethionine—8-amino-7-oxononanoate transaminase
Reaction: S-adenosyl-L-methionine + 8-amino-7-oxononanoate = S-adenosyl-4-(methylsulfanyl)-2-oxobutanoate + 7,8-diaminononanoate
Other name(s): 7,8-diaminonanoate transaminase; 7,8-diaminononanoate transaminase; DAPA transaminase (ambiguous); 7,8-diaminopelargonic acid aminotransferase; DAPA aminotransferase (ambiguous); 7-keto-8-aminopelargonic acid; diaminopelargonate synthase; 7-keto-8-aminopelargonic acid aminotransferase
Systematic name: S-adenosyl-L-methionine:8-amino-7-oxononanoate aminotransferase
Comments: A pyridoxal 5′-phosphate enzyme. S-adenosylhomocysteine can also act as donor.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 37259-71-5
References:
1.  Izumi, Y., Sato, K., Tani, Y. and Ogata, K. Purification of 7-keto-8-aminopelargonic acid-7,8-diaminopelargonic acid aminotransferase, an enzyme involved in biotin synthesis, from Brevibacterium divaricatum. Agric. Biol. Chem. 37 (1973) 2683–2684.
2.  Izumi, Y., Sato, K., Tani, Y. and Ogata, K. 7,8-Diaminopelargonic acid aminotransferase, an enzyme involved in biotin synthesis by microorganisms. Agric. Biol. Chem. 39 (1975) 175–181.
3.  Stoner, G.L. and Eisenberg, M.A. Purification and properties of 7,8-diaminopelargonic acid aminotransferase. An enzyme in the biotin biosynthetic pathway. J. Biol. Chem. 250 (1973) 4029–4036. [PMID: 1092681]
[EC 2.6.1.62 created 1983]
 
 
EC 2.6.1.66     
Accepted name: valine—pyruvate transaminase
Reaction: L-valine + pyruvate = 3-methyl-2-oxobutanoate + L-alanine
For diagram of reaction, click here, of isoleucine and valine biosynthesis, click here and for diagram of mechanism, click here
Other name(s): transaminase C; valine-pyruvate aminotransferase; alanine-oxoisovalerate aminotransferase
Systematic name: L-valine:pyruvate aminotransferase
Comments: Different from EC 2.6.1.42, branched-chain-amino-acid-transaminase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 73379-50-7
References:
1.  Falkinham, J.O. , III Identification of a mutation affecting an alanine-α-ketoisovalerate transaminase activity in Escherichia coli K-12. Mol. Gen. Genet. 176 (1979) 147–149. [PMID: 396446]
2.  Rudman, D. and Meister, A. Transamination in Escherichia coli. J. Biol. Chem. 200 (1953) 591–604. [PMID: 13034817]
[EC 2.6.1.66 created 1984]
 
 
EC 2.6.1.73     
Accepted name: methionine—glyoxylate transaminase
Reaction: L-methionine + glyoxylate = 4-(methylsulfanyl)-2-oxobutanoate + glycine
For diagram of EC 2.6.1, click here
Other name(s): methionine-glyoxylate aminotransferase; MGAT
Systematic name: L-methionine:glyoxylate aminotransferase
Comments: L-Glutamate can also act as donor.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 116155-75-0
References:
1.  Glover, J.R., Chapple, C.C.S., Rothwell, S., Tober, I. and Ellis, B.E. Allylglucosinolate biosynthesis in Brassica carinata. Phytochemistry 27 (1988) 1345–1348.
[EC 2.6.1.73 created 1992]
 
 
EC 2.6.1.88     
Accepted name: methionine transaminase
Reaction: L-methionine + a 2-oxo carboxylate = 4-(methylsulfanyl)-2-oxobutanoate + an L-amino acid
Other name(s): methionine-oxo-acid transaminase
Systematic name: L-methionine:2-oxo-acid aminotransferase
Comments: The enzyme is most active with L-methionine. It participates in the L-methionine salvage pathway from S-methyl-5′-thioadenosine, a by-product of polyamine biosynthesis. The enzyme from the bacterium Klebsiella pneumoniae can use several different amino acids as amino donor, with aromatic amino acids being the most effective [1]. The enzyme from the plant Arabidopsis thaliana is also a part of the chain elongation pathway in the biosynthesis of methionine-derived glucosinolates [3].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Heilbronn, J., Wilson, J. and Berger, B.J. Tyrosine aminotransferase catalyzes the final step of methionine recycling in Klebsiella pneumoniae. J. Bacteriol. 181 (1999) 1739–1747. [PMID: 10074065]
2.  Dolzan, M., Johansson, K., Roig-Zamboni, V., Campanacci, V., Tegoni, M., Schneider, G. and Cambillau, C. Crystal structure and reactivity of YbdL from Escherichia coli identify a methionine aminotransferase function. FEBS Lett. 571 (2004) 141–146. [DOI] [PMID: 15280032]
3.  Schuster, J., Knill, T., Reichelt, M., Gershenzon, J. and Binder, S. Branched-chain aminotransferase4 is part of the chain elongation pathway in the biosynthesis of methionine-derived glucosinolates in Arabidopsis. Plant Cell 18 (2006) 2664–2679. [DOI] [PMID: 17056707]
[EC 2.6.1.88 created 2011]
 
 
EC 2.6.1.117     
Accepted name: L-glutamine—4-(methylsulfanyl)-2-oxobutanoate aminotransferase
Reaction: L-glutamine + 4-(methylsulfanyl)-2-oxobutanoate = 2-oxoglutaramate + L-methionine
Other name(s): mtnE (gene name); Solyc11g013170.1 (locus name)
Systematic name: L-glutamine:4-(methylsulfanyl)-2-oxobutanoate aminotransferase
Comments: A pyridoxal-phosphate protein. The enzyme, found in both prokaryotes and eukaryotes, catalyses the last reaction in a methionine salvage pathway. In mammals this activity is catalysed by the multifunctional glutamine transaminase K (cf. EC 2.6.1.64, glutamine—phenylpyruvate transaminase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Berger, B.J., English, S., Chan, G. and Knodel, M.H. Methionine regeneration and aminotransferases in Bacillus subtilis, Bacillus cereus, and Bacillus anthracis. J. Bacteriol. 185 (2003) 2418–2431. [PMID: 12670965]
2.  Ellens, K.W., Richardson, L.G., Frelin, O., Collins, J., Ribeiro, C.L., Hsieh, Y.F., Mullen, R.T. and Hanson, A.D. Evidence that glutamine transaminase and ω-amidase potentially act in tandem to close the methionine salvage cycle in bacteria and plants. Phytochemistry 113 (2015) 160–169. [PMID: 24837359]
[EC 2.6.1.117 created 2019]
 
 
EC 2.7.1.37      
Transferred entry: protein kinase. Now divided into EC 2.7.11.1 (non-specific serine/threonine protein kinase), EC 2.7.11.8 (Fas-activated serine/threonine kinase), EC 2.7.11.9 (Goodpasture-antigen-binding protein kinase), EC 2.7.11.10 (IκB kinase), EC 2.7.11.11 (cAMP-dependent protein kinase), EC 2.7.11.12 (cGMP-dependent protein kinase), EC 2.7.11.13 (protein kinase C), EC 2.7.11.21 (polo kinase), EC 2.7.11.22 (cyclin-dependent kinase), EC 2.7.11.24 (mitogen-activated protein kinase), EC 2.7.11.25 (mitogen-activated protein kinase kinase kinase), EC 2.7.11.30 (receptor protein serine/threonine kinase) and EC 2.7.12.1 (dual-specificity kinase)
[EC 2.7.1.37 created 1961 (EC 2.7.1.70 incorporated 2004), deleted 2005]
 
 
EC 2.7.1.115      
Transferred entry: [3-methyl-2-oxobutanoate dehydrogenase (lipoamide)] kinase. Now EC 2.7.11.4, [3-methyl-2-oxobutanoate dehydrogenase (acetyl-transferring)] kinase
[EC 2.7.1.115 created 1986, deleted 2005]
 
 
EC 2.7.11.4     
Accepted name: [3-methyl-2-oxobutanoate dehydrogenase (acetyl-transferring)] kinase
Reaction: ATP + [3-methyl-2-oxobutanoate dehydrogenase (acetyl-transferring)] = ADP + [3-methyl-2-oxobutanoate dehydrogenase (acetyl-transferring)] phosphate
Other name(s): BCK; BCKD kinase; BCODH kinase; branched-chain α-ketoacid dehydrogenase kinase; branched-chain 2-oxo acid dehydrogenase kinase; branched-chain keto acid dehydrogenase kinase; branched-chain oxo acid dehydrogenase kinase (phosphorylating); STK2
Systematic name: ATP:[3-methyl-2-oxobutanoate dehydrogenase (acetyl-transferring)] phosphotransferase
Comments: The enzyme has no activating compound but is specific for its substrate. It is a mitochondrial enzyme associated with the branched-chain 2-oxoacid dehydrogenase complex. Phosphorylation inactivates EC 1.2.4.4, 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 82391-38-6
References:
1.  Paxton, R. and Harris, R.A. Isolation of rabbit liver branched chain α-ketoacid dehydrogenase and regulation by phosphorylation. J. Biol. Chem. 257 (1982) 14433–14439. [PMID: 7142221]
2.  Wynn, R.M., Chuang, J.L., Cote, C.D. and Chuang, D.T. Tetrameric assembly and conservation in the ATP-binding domain of rat branched-chain α-ketoacid dehydrogenase kinase. J. Biol. Chem. 275 (2000) 30512–30519. [DOI] [PMID: 10903321]
3.  Chuang, J.L., Wynn, R.M. and Chuang, D.T. The C-terminal hinge region of lipoic acid-bearing domain of E2b is essential for domain interaction with branched-chain α-keto acid dehydrogenase kinase. J. Biol. Chem. 277 (2002) 36905–36908. [DOI] [PMID: 12189132]
4.  Popov, K.M., Hawes, J.W. and Harris, R.A. Mitochondrial α-ketoacid dehydrogenase kinases: a new family of protein kinases. Adv. Second Messenger Phosphoprotein Res. 31 (1997) 105–111. [PMID: 9344245]
[EC 2.7.11.4 created 1986 as EC 2.7.1.115, transferred 2005 to EC 2.7.11.4]
 
 
EC 3.1.3.52     
Accepted name: [3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring)]-phosphatase
Reaction: [3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring)] phosphate + H2O = [3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring)] + phosphate
Glossary: lipoyl group
Other name(s): branched-chain oxo-acid dehydrogenase phosphatase; branched-chain 2-keto acid dehydrogenase phosphatase; branched-chain α-keto acid dehydrogenase phosphatase; BCKDH (ambiguous); [3-methyl-2-oxobutanoate dehydrogenase (lipoamide)]-phosphatase; [3-methyl-2-oxobutanoate dehydrogenase (lipoamide)]-phosphate phosphohydrolase
Systematic name: [3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring)]-phosphate phosphohydrolase
Comments: A mitochondrial enzyme associated with the 3-methyl-2-oxobutanoate dehydrogenase complex. Simultaneously dephosphorylates and activates EC 1.2.4.4 3-methyl-2-oxobutanoate dehydrogenase (2-methylpropanoyl-transferring), that has been inactivated by phosphorylation.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 87244-20-0, 88086-29-7
References:
1.  Fatania, H.R., Patston, P.A. and Randle, P.J. Dephosphorylation and reactivation of phosphorylated purified ox-kidney branched-chain dehydrogenase complex by co-purified phosphatase. FEBS Lett. 158 (1983) 234–238. [DOI] [PMID: 6307746]
2.  Reed, L.J., Damuni, Z. and Merryfield, M.L. Regulation of mammalian pyruvate and branched-chain α-keto acid dehydrogenase complexes by phosphorylation-dephosphorylation. Curr. Top. Cell. Regul. 27 (1985) 41–49. [DOI] [PMID: 3004826]
[EC 3.1.3.52 created 1986]
 
 
EC 3.1.3.77     
Accepted name: acireductone synthase
Reaction: 5-(methylsulfanyl)-2,3-dioxopentyl phosphate + H2O = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + phosphate (overall reaction)
(1a) 5-(methylsulfanyl)-2,3-dioxopentyl phosphate = 2-hydroxy-5-(methylsulfanyl)-3-oxopent-1-enyl phosphate (probably spontaneous)
(1b) 2-hydroxy-5-(methylsulfanyl)-3-oxopent-1-enyl phosphate + H2O = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one + phosphate
For diagram of methionine salvage, click here
Glossary: acireductone = 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one
Other name(s): E1; E-1 enolase-phosphatase; 5-(methylthio)-2,3-dioxopentyl-phosphate phosphohydrolase (isomerizing)
Systematic name: 5-(methylsulfanyl)-2,3-dioxopentyl-phosphate phosphohydrolase (isomerizing)
Comments: This bifunctional enzyme first enolizes the substrate to form the intermediate 2-hydroxy-5-(methylsulfanyl)-3-oxopent-1-enyl phosphate, which is then dephosphorylated to form the acireductone 1,2-dihydroxy-5-(methylsulfanyl)pent-1-en-3-one [2]. The acireductone represents a branch point in the methione-salvage pathway as it is used in the formation of formate, CO and 3-(methylsulfanyl)propanoate by EC 1.13.11.53 [acireductone dioxygenase (Ni2+-requiring)] and of formate and 4-(methylsulfanyl)-2-oxobutanoate either by a spontaneous reaction under aerobic conditions or by EC 1.13.11.54 {acireductone dioxygenase [iron(II)-requiring]} [1,2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Myers, R.W., Wray, J.W., Fish, S. and Abeles, R.H. Purification and characterization of an enzyme involved in oxidative carbon-carbon bond cleavage reactions in the methionine salvage pathway of Klebsiella pneumoniae. J. Biol. Chem. 268 (1993) 24785–24791. [PMID: 8227039]
2.  Wray, J.W. and Abeles, R.H. The methionine salvage pathway in Klebsiella pneumoniae and rat liver. Identification and characterization of two novel dioxygenases. J. Biol. Chem. 270 (1995) 3147–3153. [DOI] [PMID: 7852397]
3.  Wang, H., Pang, H., Bartlam, M. and Rao, Z. Crystal structure of human E1 enzyme and its complex with a substrate analog reveals the mechanism of its phosphatase/enolase activity. J. Mol. Biol. 348 (2005) 917–926. [DOI] [PMID: 15843022]
[EC 3.1.3.77 created 2006]
 
 
EC 3.5.99.7     
Accepted name: 1-aminocyclopropane-1-carboxylate deaminase
Reaction: 1-aminocyclopropane-1-carboxylate + H2O = 2-oxobutanoate + NH3 (overall reaction)
(1a) 1-aminocyclopropane-1-carboxylate = 2-aminobut-2-enoate
(1b) 2-aminobut-2-enoate = 2-iminobutanoate (spontaneous)
(1c) 2-iminobutanoate + H2O = 2-oxobutanoate + NH3 (spontaneous)
Other name(s): 1-aminocyclopropane-1-carboxylate endolyase (deaminating); ACC deaminase; 1-aminocyclopropane carboxylic acid deaminase
Systematic name: 1-aminocyclopropane-1-carboxylate aminohydrolase (isomerizing)
Comments: A pyridoxal 5′-phosphate enzyme. The enzyme, found in certain soil bacteria and fungi, catalyses the ring opening of 1-aminocyclopropane-1-carboxylate, the immediate precursor to ethylene, an important plant hormone that regulates fruit ripening and other processes. The enzyme releases an unstable enamine product that tautomerizes to an imine form, which undergoes a hydrolytic deamination. The latter reaction, which can occur spontaneously, can also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase. The enzyme has been used to make fruit ripening dependent on externally added ethylene, as it removes the substrate for endogenous ethylene formation.
Links to other databases: BRENDA, EAWAG-BBD, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 69553-48-6
References:
1.  Honma, M. and Shimomura, T. Metabolism of 1-aminocyclopropane-1-carboxylic acid. Agric. Biol. Chem. 42 (1978) 1825–1831.
2.  Yao, M., Ose, T., Sugimoto, H., Horiuchi, A., Nakagawa, A., Wakatsuki, S., Yokoi, D., Murakami, T., Honma, M. and Tanaka, I. Crystal structure of 1-aminocyclopropane-1-carboxylate deaminase from Hansenula saturnus. J. Biol. Chem. 275 (2000) 34557–34565. [DOI] [PMID: 10938279]
3.  Thibodeaux, C.J. and Liu, H.W. Mechanistic studies of 1-aminocyclopropane-1-carboxylate deaminase: characterization of an unusual pyridoxal 5′-phosphate-dependent reaction. Biochemistry 50 (2011) 1950–1962. [DOI] [PMID: 21244019]
[EC 3.5.99.7 created 1981 as EC 4.1.99.4, transferred 2002 to EC 3.5.99.7, modified 2014]
 
 
EC 3.5.99.10     
Accepted name: 2-iminobutanoate/2-iminopropanoate deaminase
Reaction: (1) 2-iminobutanoate + H2O = 2-oxobutanoate + NH3
(2) 2-iminopropanoate + H2O = pyruvate + NH3
Other name(s): yjgF (gene name); ridA (gene name); enamine/imine deaminase (ambiguous)
Systematic name: 2-iminobutanoate aminohydrolase
Comments: This enzyme, which has been found in all species and tissues examined, catalyses the hydrolytic deamination of imine intermediates formed by several types of pyridoxal-5′-phosphate-dependent dehydratases, such as EC 4.3.1.19, threonine ammonia-lyase and EC 4.3.1.17, L-serine ammonia-lyase. The reactions, which can occur spontaneously, are accelerated to minimize the cellular damage that could be caused by these reactive intermediates.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Lambrecht, J.A., Flynn, J.M. and Downs, D.M. Conserved YjgF protein family deaminates reactive enamine/imine intermediates of pyridoxal 5′-phosphate (PLP)-dependent enzyme reactions. J. Biol. Chem. 287 (2012) 3454–3461. [DOI] [PMID: 22094463]
[EC 3.5.99.10 created 2014]
 
 
EC 4.1.2.12     
Accepted name: 2-dehydropantoate aldolase
Reaction: 2-dehydropantoate = 3-methyl-2-oxobutanoate + formaldehyde
Glossary: pantoate = 2,4-dihydroxy-3,3-dimethylbutanoate
Other name(s): ketopantoaldolase; 2-dehydropantoate formaldehyde-lyase
Systematic name: 2-dehydropantoate formaldehyde-lyase (3-methyl-2-oxobutanoate-forming)
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9024-51-5
References:
1.  McIntosh, E.N., Purko, M. and Wood, W.A. Ketopantoate formation by a hydroxymethylation enzyme from Escherichia coli. J. Biol. Chem. 228 (1957) 499–510. [PMID: 13475336]
[EC 4.1.2.12 created 1965, modified 2002]
 
 
EC 4.1.2.14     
Accepted name: 2-dehydro-3-deoxy-phosphogluconate aldolase
Reaction: 2-dehydro-3-deoxy-6-phospho-D-gluconate = pyruvate + D-glyceraldehyde 3-phosphate
For diagram of the Entner-Doudoroff pathway, click here
Other name(s): phospho-2-keto-3-deoxygluconate aldolase; KDPG aldolase; phospho-2-keto-3-deoxygluconic aldolase; 2-keto-3-deoxy-6-phosphogluconic aldolase; 2-keto-3-deoxy-6-phosphogluconate aldolase; 6-phospho-2-keto-3-deoxygluconate aldolase; ODPG aldolase; 2-oxo-3-deoxy-6-phosphogluconate aldolase; 2-keto-3-deoxygluconate-6-P-aldolase; 2-keto-3-deoxygluconate-6-phosphate aldolase; 2-dehydro-3-deoxy-D-gluconate-6-phosphate D-glyceraldehyde-3-phosphate-lyase; 2-dehydro-3-deoxy-D-gluconate-6-phosphate D-glyceraldehyde-3-phosphate-lyase (pyruvate-forming)
Systematic name: 2-dehydro-3-deoxy-6-phospho-D-gluconate D-glyceraldehyde-3-phosphate-lyase (pyruvate-forming)
Comments: The enzyme shows no activity with 2-dehydro-3-deoxy-6-phosphate-D-galactonate. cf. EC 4.1.2.55, 2-dehydro-3-deoxy-phosphogluconate/2-dehydro-3-deoxy-6-phosphogalactonate aldolase [2]. Also acts on 2-oxobutanoate [1].
Links to other databases: BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9024-53-7
References:
1.  Meloche, H.P. and Wood, W.A. Crystallization and characteristics of 2-keto-3-deoxy-6-phosphogluconic aldolase. J. Biol. Chem. 239 (1964) 3515–3518. [PMID: 14245411]
2.  Barran, L.R. and Wood, W.A. The mechanism of 2-keto-3-deoxy-6-phosphogluconate aldolase. 3. Nature of the inactivation by fluorodinitrobenzene. J. Biol. Chem. 246 (1971) 4028–4035. [PMID: 5561473]
[EC 4.1.2.14 created 1965, modified 1976, modified 2014]
 
 
EC 4.1.2.52     
Accepted name: 4-hydroxy-2-oxoheptanedioate aldolase
Reaction: 4-hydroxy-2-oxoheptanedioate = pyruvate + succinate semialdehyde
Other name(s): 2,4-dihydroxyhept-2-enedioate aldolase; HHED aldolase; 4-hydroxy-2-ketoheptanedioate aldolase; HKHD aldolase; HpcH; HpaI; 4-hydroxy-2-oxoheptanedioate succinate semialdehyde lyase (pyruvate-forming)
Systematic name: 4-hydroxy-2-oxoheptanedioate succinate-semialdehyde-lyase (pyruvate-forming)
Comments: Requires Co2+ or Mn2+ for activity. The enzyme is also able to catalyse the aldol cleavage of 4-hydroxy-2-oxopentanoate and 4-hydroxy-2-oxohexanoate, and can use 2-oxobutanoate as carbonyl donor, with lower efficiency. In the reverse direction, is able to condense a range of aldehyde acceptors with pyruvate. The enzyme from the bacterium Escherichia coli produces a racemic mixture of (4R)- and (4S)-hydroxy-2-oxoheptanedioate [4].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Wang, W. and Seah, S.Y. Purification and biochemical characterization of a pyruvate-specific class II aldolase, HpaI. Biochemistry 44 (2005) 9447–9455. [DOI] [PMID: 15996099]
2.  Rea, D., Fulop, V., Bugg, T.D. and Roper, D.I. Structure and mechanism of HpcH: a metal ion dependent class II aldolase from the homoprotocatechuate degradation pathway of Escherichia coli. J. Mol. Biol. 373 (2007) 866–876. [DOI] [PMID: 17881002]
3.  Wang, W. and Seah, S.Y. The role of a conserved histidine residue in a pyruvate-specific class II aldolase. FEBS Lett. 582 (2008) 3385–3388. [DOI] [PMID: 18775708]
4.  Wang, W., Baker, P. and Seah, S.Y.K. Comparison of two metal-dependent pyruvate aldolases related by convergent evolution: substrate specificity, kinetic mechanism, and substrate channeling. Biochemistry 49 (2010) 3774–3782. [DOI] [PMID: 20364820]
[EC 4.1.2.52 created 2013]
 
 
EC 4.2.1.9     
Accepted name: dihydroxy-acid dehydratase
Reaction: 2,3-dihydroxy-3-methylbutanoate = 3-methyl-2-oxobutanoate + H2O
For diagram of isoleucine and valine biosynthesis, click here
Other name(s): acetohydroxyacid dehydratase; α,β-dihydroxyacid dehydratase; 2,3-dihydroxyisovalerate dehydratase; α,β-dihydroxyisovalerate dehydratase; dihydroxy acid dehydrase; DHAD; 2,3-dihydroxy-acid hydro-lyase
Systematic name: 2,3-dihydroxy-3-methylbutanoate hydro-lyase (3-methyl-2-oxobutanoate-forming)
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9024-32-2
References:
1.  Kanamori, M. and Wixom, R.L. Studies in valine biosynthesis. V. Characteristics of the purified dihydroxyacid dehydratase from spinach leaves. J. Biol. Chem. 238 (1963) 998–1005. [PMID: 13962154]
2.  Myers, J.W. Dihydroxy acid dehydrase: an enzyme involved in the biosynthesis of isoleucine and valine. J. Biol. Chem. 236 (1961) 1414–1418. [PMID: 13727223]
[EC 4.2.1.9 created 1961]
 
 
EC 4.3.1.19     
Accepted name: threonine ammonia-lyase
Reaction: L-threonine = 2-oxobutanoate + NH3 (overall reaction)
(1a) L-threonine = 2-aminobut-2-enoate + H2O
(1b) 2-aminobut-2-enoate = 2-iminobutanoate (spontaneous)
(1c) 2-iminobutanoate + H2O = 2-oxobutanoate + NH3 (spontaneous)
For diagram of isoleucine and valine biosynthesis, click here
Other name(s): threonine deaminase; L-serine dehydratase; serine deaminase; L-threonine dehydratase; threonine dehydrase; L-threonine deaminase; threonine dehydratase; L-threonine hydro-lyase (deaminating); L-threonine ammonia-lyase
Systematic name: L-threonine ammonia-lyase (2-oxobutanoate-forming)
Comments: Most enzymes that catalyse this reaction are pyridoxal-phosphate-dependent, although some enzymes contain an iron-sulfur cluster instead. The reaction catalysed by both types of enzymes involves the initial elimination of water to form an enamine intermediate (hence the enzyme’s original classification as EC 4.2.1.16, threonine dehydratase), followed by tautomerization to an imine form and hydrolysis of the C-N bond [3,5]. The latter reaction, which can occur spontaneously, is also be catalysed by EC 3.5.99.10, 2-iminobutanoate/2-iminopropanoate deaminase [5]. The enzymes from a number of sources also act on L-serine, cf. EC 4.3.1.17, L-serine ammonia-lyase.
Links to other databases: BRENDA, EAWAG-BBD, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 774231-81-1
References:
1.  Cohn, M.S. and Phillips, A.T. Purification and characterization of a B6-independent threonine dehydratase from Pseudomonas putida. Biochemistry 13 (1974) 1208–1214. [PMID: 4814721]
2.  Nishimura, J.S. and Greenberg, D.M. Purification and properties of L-threonine dehydrase of sheep liver. J. Biol. Chem. 236 (1961) 2684–2691. [PMID: 14479973]
3.  Phillips, A.T. and Wood, W.A. The mechanism of action of 5′-adenylic acid-activated threonine dehydrase. J. Biol. Chem. 240 (1965) 4703–4709. [PMID: 5321308]
4.  Shizuta, Y., Nakazawa, A., Tokushige, M. and Hayaishi, O. Studies on the interaction between regulatory enzymes and effectors. 3. Crystallization and characterization of adenosine 5′-monophosphate-dependent threonine deaminase from Escherichia coli. J. Biol. Chem. 244 (1969) 1883–1889. [PMID: 4889010]
5.  Lambrecht, J.A., Flynn, J.M. and Downs, D.M. Conserved YjgF protein family deaminates reactive enamine/imine intermediates of pyridoxal 5′-phosphate (PLP)-dependent enzyme reactions. J. Biol. Chem. 287 (2012) 3454–3461. [DOI] [PMID: 22094463]
[EC 4.3.1.19 created 1961 as EC 4.2.1.16, transferred 2001 to EC 4.3.1.19, modified 2014]
 
 


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