The Enzyme Database

Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB)

Proposed Changes to the Enzyme List

The entries below are proposed additions and amendments to the Enzyme Nomenclature list. They were prepared for the NC-IUBMB by Kristian Axelsen, Richard Cammack, Ron Caspi, Masaaki Kotera, Andrew McDonald, Gerry Moss, Dietmar Schomburg, Ida Schomburg and Keith Tipton. Comments and suggestions on these draft entries should be sent to Dr Andrew McDonald (Department of Biochemistry, Trinity College Dublin, Dublin 2, Ireland). The date on which an enzyme will be made official is appended after the EC number. To prevent confusion please do not quote new EC numbers until they are incorporated into the main list.

An asterisk before 'EC' indicates that this is an amendment to an existing enzyme rather than a new enzyme entry.


Contents

EC 1.1.1.292 1,5-anhydro-D-fructose reductase (1,5-anhydro-D-mannitol-forming)
EC 2.1.1.158 7-methylxanthosine synthase
EC 2.1.1.159 theobromine synthase
EC 2.1.1.160 caffeine synthase
EC 2.4.1.112 deleted
EC 2.4.1.186 glycogenin glucosyltransferase
*EC 2.4.1.186 glycogenin glucosyltransferase
EC 2.5.1.67 chrysanthemyl diphosphate synthase
EC 2.5.1.68 (2Z,6E)-farnesyl diphosphate synthase
EC 2.5.1.69 lavandulyl diphosphate synthase
EC 2.8.1.6 biotin synthase
EC 3.2.2.25 N-methyl nucleosidase
*EC 4.2.1.79 2-methylcitrate dehydratase
EC 4.2.1.112 acetylene hydratase
EC 4.2.3.27 isoprene synthase


EC 1.1.1.292
Accepted name: 1,5-anhydro-D-fructose reductase (1,5-anhydro-D-mannitol-forming)
Reaction: 1,5-anhydro-D-mannitol + NADP+ = 1,5-anhydro-D-fructose + NADPH + H+
Other name(s): 1,5-anhydro-D-fructose reductase (ambiguous); AFR
Systematic name: 1,5-anhydro-D-mannitol:NADP+ oxidoreductase
Comments: This enzyme is present in some but not all Rhizobium species and belongs in the GFO/IDH/MocA protein family [2]. This enzyme differs from hepatic 1,5-anhydro-D-fructose reductase, which yields 1,5-anhydro-D-glucitol as the product (see EC 1.1.1.263). In Sinorhizobium morelense, the product of the reaction, 1,5-anhydro-D-mannitol, can be further metabolized to D-mannose [1]. The enzyme also reduces 1,5-anhydro-D-erythro-hexo-2,3-diulose and 2-ketoaldoses (called osones), such as D-glucosone (D-arabino-hexos-2-ulose) and 6-deoxy-D-glucosone. It does not reduce common aldoses and ketoses, or non-sugar aldehydes and ketones [1].
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG, UM-BBD
References:
1.  Kühn, A., Yu, S. and Giffhorn, F. Catabolism of 1,5-anhydro-D-fructose in Sinorhizobium morelense S-30.7.5: discovery, characterization, and overexpression of a new 1,5-anhydro-D-fructose reductase and its application in sugar analysis and rare sugar synthesis. Appl. Environ. Microbiol. 72 (2006) 1248–1257. [PMID: 16461673]
2.  Dambe, T.R., Kühn, A.M., Brossette, T., Giffhorn, F. and Scheidig, A.J. Crystal structure of NADP(H)-dependent 1,5-anhydro-D-fructose reductase from Sinorhizobium morelense at 2.2 Å resolution: construction of a NADH-accepting mutant and its application in rare sugar synthesis. Biochemistry 45 (2006) 10030–10042. [PMID: 16906761]
[EC 1.1.1.292 created 2007]
 
 
EC 2.1.1.158
Accepted name: 7-methylxanthosine synthase
Reaction: S-adenosyl-L-methionine + xanthosine = S-adenosyl-L-homocysteine + 7-methylxanthosine
For diagram of caffeine biosynthesis, click here
Other name(s): xanthosine methyltransferase; XMT; xanthosine:S-adenosyl-L-methionine methyltransferase; CtCS1; CmXRS1; CaXMT1; S-adenosyl-L-methionine:xanthosine 7-N-methyltransferase
Systematic name: S-adenosyl-L-methionine:xanthosine N7-methyltransferase
Comments: The enzyme is specific for xanthosine, as XMP and xanthine cannot act as substrates [2,4]. The enzyme does not have N1- or N3- methylation activity [2]. This is the first methylation step in the production of caffeine.
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG
References:
1.  Negishi, O., Ozawa, T. and Imagawa, H. The role of xanthosine in the biosynthesis of caffeine in coffee plants. Agric. Biol. Chem. 49 (1985) 2221–2222.
2.  Mizuno, K., Kato, M., Irino, F., Yoneyama, N., Fujimura, T. and Ashihara, H. The first committed step reaction of caffeine biosynthesis: 7-methylxanthosine synthase is closely homologous to caffeine synthases in coffee (Coffea arabica L.). FEBS Lett. 547 (2003) 56–60. [PMID: 12860386]
3.  Uefuji, H., Ogita, S., Yamaguchi, Y., Koizumi, N. and Sano, H. Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants. Plant Physiol. 132 (2003) 372–380. [PMID: 12746542]
4.  Yoneyama, N., Morimoto, H., Ye, C.X., Ashihara, H., Mizuno, K. and Kato, M. Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme. Mol. Genet. Genomics 275 (2006) 125–135. [PMID: 16333668]
[EC 2.1.1.158 created 2007]
 
 
EC 2.1.1.159
Accepted name: theobromine synthase
Reaction: S-adenosyl-L-methionine + 7-methylxanthine = S-adenosyl-L-homocysteine + 3,7-dimethylxanthine
For diagram of caffeine biosynthesis, click here
Glossary: theobromine = 3,7-dimethylxanthine
paraxanthine = 1,7-dimethylxanthine
Other name(s): monomethylxanthine methyltransferase; MXMT; CTS1; CTS2; S-adenosyl-L-methionine:7-methylxanthine 3-N-methyltransferase
Systematic name: S-adenosyl-L-methionine:7-methylxanthine N3-methyltransferase
Comments: This is the third enzyme in the caffeine-biosynthesis pathway. This enzyme can also catalyse the conversion of paraxanthine into caffeine, although the paraxanthine pathway is considered to be a minor pathway for caffeine biosynthesis [2,3].
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG
References:
1.  Ogawa, M., Herai, Y., Koizumi, N., Kusano, T. and Sano, H. 7-Methylxanthine methyltransferase of coffee plants. Gene isolation and enzymatic properties. J. Biol. Chem. 276 (2001) 8213–8218. [PMID: 11108716]
2.  Uefuji, H., Ogita, S., Yamaguchi, Y., Koizumi, N. and Sano, H. Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants. Plant Physiol. 132 (2003) 372–380. [PMID: 12746542]
3.  Yoneyama, N., Morimoto, H., Ye, C.X., Ashihara, H., Mizuno, K. and Kato, M. Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme. Mol. Genet. Genomics 275 (2006) 125–135. [PMID: 16333668]
[EC 2.1.1.159 created 2007]
 
 
EC 2.1.1.160
Accepted name: caffeine synthase
Reaction: (1) S-adenosyl-L-methionine + 3,7-dimethylxanthine = S-adenosyl-L-homocysteine + 1,3,7-trimethylxanthine
(2) S-adenosyl-L-methionine + 1,7-dimethylxanthine = S-adenosyl-L-homocysteine + 1,3,7-trimethylxanthine
(3) S-adenosyl-L-methionine + 7-methylxanthine = S-adenosyl-L-homocysteine + 3,7-dimethylxanthine
For diagram of caffeine biosynthesis, click here
Glossary: theobromine = 3,7-dimethylxanthine
paraxanthine = 1,7-dimethylxanthine
caffeine = 1,3,7-trimethylxanthine
Other name(s): dimethylxanthine methyltransferase; 3N-methyltransferase; DXMT; CCS1; S-adenosyl-L-methionine:3,7-dimethylxanthine 1-N-methyltransferase
Systematic name: S-adenosyl-L-methionine:3,7-dimethylxanthine N1-methyltransferase
Comments: Paraxanthine is the best substrate for this enzyme but the paraxanthine pathway is considered to be a minor pathway for caffeine biosynthesis [2,3].
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG
References:
1.  Kato, M., Mizuno, K., Fujimura, T., Iwama, M., Irie, M., Crozier, A. and Ashihara, H. Purification and characterization of caffeine synthase from tea leaves. Plant Physiol. 120 (1999) 579–586. [PMID: 10364410]
2.  Mizuno, K., Okuda, A., Kato, M., Yoneyama, N., Tanaka, H., Ashihara, H. and Fujimura, T. Isolation of a new dual-functional caffeine synthase gene encoding an enzyme for the conversion of 7-methylxanthine to caffeine from coffee (Coffea arabica L.). FEBS Lett. 534 (2003) 75–81. [PMID: 12527364]
3.  Uefuji, H., Ogita, S., Yamaguchi, Y., Koizumi, N. and Sano, H. Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants. Plant Physiol. 132 (2003) 372–380. [PMID: 12746542]
4.  Kato, M., Mizuno, K., Crozier, A., Fujimura, T. and Ashihara, H. Caffeine synthase gene from tea leaves. Nature 406 (2000) 956–957. [PMID: 10984041]
[EC 2.1.1.160 created 2007]
 
 
EC 2.4.1.112
Deleted entry: α-1,4-glucan-protein synthase (UDP-forming). The protein referred to in this entry is now known to be glycogenin so the entry has been incorporated into EC 2.4.1.186, glycogenin glucosyltransferase
[EC 2.4.1.112 created 1984, deleted 2007]
 
 
*EC 2.4.1.186
Accepted name: glycogenin glucosyltransferase
Reaction: UDP-α-D-glucose + glycogenin = UDP + α-D-glucosylglycogenin
Other name(s): glycogenin; priming glucosyltransferase; UDP-glucose:glycogenin glucosyltransferase
Systematic name: UDP-α-D-glucose:glycogenin α-D-glucosyltransferase
Comments: The first reaction of this enzyme is to catalyse its own glucosylation, normally at Tyr-194 of the protein if this group is free. When Tyr-194 is replaced by Thr or Phe, the enzyme’s Mn2+-dependent self-glucosylation activity is lost but its intermolecular transglucosylation ability remains [7]. It continues to glucosylate an existing glucosyl group until a length of about 5–13 residues has been formed. Further lengthening of the glycogen chain is then carried out by EC 2.4.1.11, glycogen (starch) synthase. The enzyme is not highly specific for the donor, using UDP-xylose in addition to UDP-glucose (although not glucosylating or xylosylating a xylosyl group so added). It can also use CDP-glucose and TDP-glucose, but not ADP-glucose or GDP-glucose. Similarly it is not highly specific for the acceptor, using water (i.e. hydrolysing UDP-glucose) among others. Various forms of the enzyme exist, and different forms predominate in different organs. Thus primate liver contains glycogenin-2, of molecular mass 66 kDa, whereas the more widespread form is glycogenin-1, with a molecular mass of 38 kDa.
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG, PDB, CAS registry number: 117590-73-5
References:
1.  Krisman, C.R. and Barengo, R. A precursor of glycogen biosynthesis: α-1,4-glucan-protein. Eur. J. Biochem. 52 (1975) 117–123. [PMID: 809265]
2.  Pitcher, J., Smythe, C., Campbell, D.G. and Cohen, P. Identification of the 38-kDa subunit of rabbit skeletal muscle glycogen synthase as glycogenin. Eur. J. Biochem. 169 (1987) 497–502. [PMID: 3121316]
3.  Pitcher, J., Smythe, C. and Cohen, P. Glycogenin is the priming glucosyltransferase required for the initiation of glycogen biogenesis in rabbit skeletal muscle. Eur. J. Biochem. 176 (1988) 391–395. [PMID: 2970965]
4.  Kennedy, L.D., Kirkman, B.R., Lomako, J., Rodriguez, I.R. and Whelan, W.J. The biogenesis of rabbit-muscle glycogen. In: Berman, M.C. and Opie, L.A. (Eds), Membranes and Muscle, ICSU Press/IRL Press, Oxford, 1985, pp. 65–84.
5.  Rodriguez, I.R. and Whelan, W.J. A novel glycosyl-amino acid linkage: rabbit-muscle glycogen is covalently linked to a protein via tyrosine. Biochem. Biophys. Res. Commun. 132 (1985) 829–836. [PMID: 4062948]
6.  Lomako, J., Lomako, W.M. and Whelan, W.J. A self-glucosylating protein is the primer for rabbit muscle glycogen biosynthesis. FASEB J. 2 (1988) 3097–3103. [PMID: 2973423]
7.  Alonso, M.D., Lomako, J., Lomako, W.M. and Whelan, W.J. Catalytic activities of glycogenin additional to autocatalytic self-glucosylation. J. Biol. Chem. 270 (1995) 15315–15319. [PMID: 7797519]
8.  Alonso, M.D., Lomako, J., Lomako, W.M. and Whelan, W.J. A new look at the biogenesis of glycogen. FASEB J. 9 (1995) 1126–1137. [PMID: 7672505]
9.  Mu, J. and Roach, P.J. Characterization of human glycogenin-2, a self-glucosylating initiator of liver glycogen metabolism. J. Biol. Chem. 273 (1998) 34850–34856. [PMID: 9857012]
10.  Gibbons, B.J., Roach, P.J. and Hurley, T.D. Crystal structure of the autocatalytic initiator of glycogen biosynthesis, glycogenin. J. Mol. Biol. 319 (2002) 463. [PMID: 12051921]
[EC 2.4.1.186 created 1992 (EC 2.4.1.112 created 1984, incorporated 2007)]
 
 
EC 2.5.1.67
Accepted name: chrysanthemyl diphosphate synthase
Reaction: 2 dimethylallyl diphosphate = diphosphate + chrysanthemyl diphosphate
For diagram of reaction, click here
Other name(s): CPPase
Systematic name: dimethylallyl-diphosphate:dimethylallyl-diphosphate dimethylallyltransferase (chrysanthemyl-diphosphate-forming)
Comments: Requires a divalent metal ion for activity, with Mg2+ being better than Mn2+ [1]. Chrysanthemyl diphosphate is a monoterpene with a non-head-to-tail linkage. It is unlike most monoterpenoids, which are derived from geranyl diphosphate and have isoprene units that are linked head-to-tail. The mechanism of its formation is similar to that of the early steps of squalene and phytoene biosynthesis. Chrysanthemyl diphosphate is the precursor of chrysanthemic acid, the acid half of the pyrethroid insecticides found in chrysanthemums.
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG
References:
1.  Rivera, S.B., Swedlund, B.D., King, G.J., Bell, R.N., Hussey, C.E., Jr., Shattuck-Eidens, D.M., Wrobel, W.M., Peiser, G.D. and Poulter, C.D. Chrysanthemyl diphosphate synthase: isolation of the gene and characterization of the recombinant non-head-to-tail monoterpene synthase from Chrysanthemum cinerariaefolium. Proc. Natl. Acad. Sci. USA 98 (2001) 4373–4378. [PMID: 11287653]
2.  Erickson, H.K. and Poulter, C.D. Chrysanthemyl diphosphate synthase. The relationship among chain elongation, branching, and cyclopropanation reactions in the isoprenoid biosynthetic pathway. J. Am. Chem. Soc. 125 (2003) 6886–6888. [PMID: 12783539]
[EC 2.5.1.67 created 2007]
 
 
EC 2.5.1.68
Accepted name: (2Z,6E)-farnesyl diphosphate synthase
Reaction: geranyl diphosphate + isopentenyl diphosphate = diphosphate + (2Z,6E)-farnesyl diphosphate
For diagram of trans-polycis-polyprenol diphosphate biosynthesis, click here
Other name(s): (Z)-farnesyl diphosphate synthase; Z-farnesyl diphosphate synthase
Systematic name: geranyl-diphosphate:isopentenyl-diphosphate geranylcistransferase
Comments: Requires Mg2+ or Mn2+ for activity. The product of this reaction is an intermediate in the synthesis of decaprenyl phosphate, which plays a central role in the biosynthesis of most features of the mycobacterial cell wall, including peptidoglycan, linker unit galactan and arabinan. Neryl diphosphate can also act as substrate.
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG
References:
1.  Schulbach, M.C., Mahapatra, S., Macchia, M., Barontini, S., Papi, C., Minutolo, F., Bertini, S., Brennan, P.J. and Crick, D.C. Purification, enzymatic characterization, and inhibition of the Z-farnesyl diphosphate synthase from Mycobacterium tuberculosis. J. Biol. Chem. 276 (2001) 11624–11630. [PMID: 11152452]
[EC 2.5.1.68 created 2007, modified 2010]
 
 
EC 2.5.1.69
Accepted name: lavandulyl diphosphate synthase
Reaction: 2 dimethylallyl diphosphate = diphosphate + lavandulyl diphosphate
For diagram of reaction, click here
Other name(s): FDS-5
Systematic name: dimethylallyl-diphosphate:dimethylallyl-diphosphate dimethylallyltransferase (lavandulyl-diphosphate-forming)
Comments: Lavandulyl diphosphate is a monoterpene with a non-head-to-tail linkage. It is unlike most monoterpenoids, which are derived from geranyl diphosphate and have isoprene units that are linked head-to-tail. When this enzyme is incubated with dimethylallyl diphosphate and isopentenyl diphosphate, it also forms the regular monoterpene geranyl diphosphate [2]. The enzyme from Artemisia tridentata (big sagebrush) forms both lavandulyl diphosphate and chrysanthemyl diphosphate (see EC 2.5.1.67, chrysanthemyl diphosphate synthase) when dimethylally diphosphate is the sole substrate.
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG
References:
1.  Erickson, H.K. and Poulter, C.D. Chrysanthemyl diphosphate synthase. The relationship among chain elongation, branching, and cyclopropanation reactions in the isoprenoid biosynthetic pathway. J. Am. Chem. Soc. 125 (2003) 6886–6888. [PMID: 12783539]
2.  Hemmerlin, A., Rivera, S.B., Erickson, H.K. and Poulter, C.D. Enzymes encoded by the farnesyl diphosphate synthase gene family in the Big Sagebrush Artemisia tridentata ssp. spiciformis. J. Biol. Chem. 278 (2003) 32132–32140. [PMID: 12782626]
[EC 2.5.1.69 created 2007]
 
 
EC 2.8.1.6
Accepted name: biotin synthase
Reaction: dethiobiotin + sulfur-(sulfur carrier) + 2 S-adenosyl-L-methionine + 2 reduced [2Fe-2S] ferredoxin = biotin + (sulfur carrier) + 2 L-methionine + 2 5′-deoxyadenosine + 2 oxidized [2Fe-2S] ferredoxin
Other name(s): dethiobiotin:sulfur sulfurtransferase
Systematic name: dethiobiotin:sulfur-(sulfur carrier) sulfurtransferase
Comments: The enzyme binds a [4Fe-4S] and a [2Fe-2S] cluster. In every reaction cycle, the enzyme consumes two molecules of AdoMet, each producing 5′-deoxyadenosine and a putative dethiobiotinyl carbon radical. Reaction with another equivalent of AdoMet results in abstraction of the C6 methylene pro-S hydrogen atom from 9-mercaptodethiobiotin, and the resulting carbon radical is quenched via formation of an intramolecular C-S bond, thus closing the biotin thiophane ring. The sulfur donor is believed to be the [2Fe-2S] cluster, which is sacrificed in the process, so that in vitro the reaction is a single turnover. In vivo, the [2Fe-2S] cluster can be reassembled by the Isc or Suf iron-sulfur cluster assembly systems, to allow further catalysis.
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG, PDB, CAS registry number: 80146-93-6
References:
1.  Trainor, D.A., Parry, R.J. and Gitterman, A. Biotin biosynthesis. 2. Stereochemistry of sulfur introduction at C-4 of dethiobiotin. J. Am. Chem. Soc. 102 (1980) 1467–1468.
2.  Shiuan, D. and Campbell, A. Transcriptional regulation and gene arrangement of Escherichia coli, Citrobacter freundii and Salmonella typhimurium biotin operons. Gene 67 (1988) 203–211. [PMID: 2971595]
3.  Zhang, S., Sanyal, I., Bulboaca, G.H., Rich, A. and Flint, D.H. The gene for biotin synthase from Saccharomyces cerevisiae: cloning, sequencing, and complementation of Escherichia coli strains lacking biotin synthase. Arch. Biochem. Biophys. 309 (1994) 29–35. [PMID: 8117110]
4.  Ugulava, N.B., Gibney, B.R. and Jarrett, J.T. Biotin synthase contains two distinct iron-sulfur cluster binding sites: chemical and spectroelectrochemical analysis of iron-sulfur cluster interconversions. Biochemistry 40 (2001) 8343–8351. [PMID: 11444981]
5.  Berkovitch, F., Nicolet, Y., Wan, J.T., Jarrett, J.T. and Drennan, C.L. Crystal structure of biotin synthase, an S-adenosylmethionine-dependent radical enzyme. Science 303 (2004) 76–79. [PMID: 14704425]
6.  Lotierzo, M., Tse Sum Bui, B., Florentin, D., Escalettes, F. and Marquet, A. Biotin synthase mechanism: an overview. Biochem. Soc. Trans. 33 (2005) 820–823. [PMID: 16042606]
7.  Taylor, A.M., Farrar, C.E. and Jarrett, J.T. 9-Mercaptodethiobiotin is formed as a competent catalytic intermediate by Escherichia coli biotin synthase. Biochemistry 47 (2008) 9309–9317. [PMID: 18690713]
8.  Reyda, M.R., Fugate, C.J. and Jarrett, J.T. A complex between biotin synthase and the iron-sulfur cluster assembly chaperone HscA that enhances in vivo cluster assembly. Biochemistry 48 (2009) 10782–10792. [PMID: 19821612]
[EC 2.8.1.6 created 1999, modified 2006, modified 2011, modified 2014]
 
 
EC 3.2.2.25
Accepted name: N-methyl nucleosidase
Reaction: 7-methylxanthosine + H2O = 7-methylxanthine + D-ribose
For diagram of caffeine biosynthesis, click here
Other name(s): 7-methylxanthosine nucleosidase; N-MeNase; N-methyl nucleoside hydrolase; methylpurine nucleosidase
Systematic name: 7-methylxanthosine ribohydrolase
Comments: The enzyme preferentially hydrolyses 3- and 7-methylpurine nucleosides, such as 3-methylxanthosine, 3-methyladenosine and 7-methylguanosine. Hydrolysis of 7-methylxanthosine to form 7-methylxanthine is the second step in the caffeine-biosynthesis pathway.
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG
References:
1.  Negishi, O., Ozawa, T. and Imagawa, H. N-Methyl nucleosidase from tea leaves. Agric. Biol. Chem. 52 (1988) 169–175.
[EC 3.2.2.25 created 2007]
 
 
*EC 4.2.1.79
Accepted name: 2-methylcitrate dehydratase
Reaction: (2S,3S)-2-hydroxybutane-1,2,3-tricarboxylate = (Z)-but-2-ene-1,2,3-tricarboxylate + H2O
Glossary: (2S,3S)-2-methylcitrate = (2S,3S)-2-hydroxybutane-1,2,3-tricarboxylate
cis-2-methylaconitate = (Z)-but-2-ene-1,2,3-tricarboxylate
Other name(s): 2-methylcitrate hydro-lyase; PrpD; 2-hydroxybutane-1,2,3-tricarboxylate hydro-lyase
Systematic name: (2S,3S)-2-hydroxybutane-1,2,3-tricarboxylate hydro-lyase [(Z)-but-2-ene-1,2,3-tricarboxylate-forming]
Comments: The enzyme is specific for (2S,3S)-methylcitrate, showing no activity with (2R,3S)-methylcitrate [2]. The enzyme can also use cis-aconitate as a substrate but more slowly [2]. Both this enzyme and EC 4.2.1.3, aconitate hydratase, are required to complete the isomerization of (2S,3S)-methylcitrate to (2R,3S)-2-methylisocitrate [2].
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG, PDB, CAS registry number: 80891-26-5
References:
1.  Aoki, H. and Tabuchi, T. Purification and properties of 2-methylcitrate dehydratase from Yarrowia lipolytica. Agric. Biol. Chem. 45 (1981) 2831–2837.
2.  Brock, M., Maerker, C., Schütz, A., Völker, U. and Buckel, W. Oxidation of propionate to pyruvate in Escherichia coli. Involvement of methylcitrate dehydratase and aconitase. Eur. J. Biochem. 269 (2002) 6184–6194. [PMID: 12473114]
[EC 4.2.1.79 created 1984]
 
 
EC 4.2.1.112
Accepted name: acetylene hydratase
Reaction: acetaldehyde = acetylene + H2O
Other name(s): AH; acetaldehyde hydro-lyase
Systematic name: acetaldehyde hydro-lyase (acetylene-forming)
Comments: This is a non-redox-active enzyme that contains two molybdopterin guanine dinucleotide (MGD) cofactors, a tungsten centre and a cubane type [4Fe-4S] cluster [2].The tungsten centre binds a water molecule that is activated by an adjacent aspartate residue, enabling it to attack acetylene bound in a distinct hydrophobic pocket [2]. Ethylene cannot act as a substrate [1].
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG, UM-BBD, CAS registry number: 75788-81-7
References:
1.  Rosner, B.M. and Schink, B. Purification and characterization of acetylene hydratase of Pelobacter acetylenicus, a tungsten iron-sulfur protein. J. Bacteriol. 177 (1995) 5767–5772. [PMID: 7592321]
2.  Seiffert, G.B., Ullmann, G.M., Messerschmidt, A., Schink, B., Kroneck, P.M. and Einsle, O. Structure of the non-redox-active tungsten/[4Fe:4S] enzyme acetylene hydratase. Proc. Natl. Acad. Sci. USA 104 (2007) 3073–3077. [PMID: 17360611]
[EC 4.2.1.112 created 2007]
 
 
EC 4.2.3.27
Accepted name: isoprene synthase
Reaction: dimethylallyl diphosphate = isoprene + diphosphate
For diagram of reaction, click here
Glossary: isoprene = 2-methylbuta-1,3-diene
Other name(s): ISPC; ISPS
Systematic name: dimethylallyl-diphosphate diphosphate-lyase (isoprene-forming)
Comments: Requires Mg2+ or Mn2+ for activity. This enzyme is located in the chloroplast of isoprene-emitting plants, such as poplar and aspen, and may be activitated by light-dependent changes in chloroplast pH and Mg2+ concentration [2,8].
Links to other databases: BRENDA, EXPASY, IUBMB, KEGG, CAS registry number: 139172-14-8
References:
1.  Silver, G.M. and Fall, R. Enzymatic synthesis of isoprene from dimethylallyl diphosphate in aspen leaf extracts. Plant Physiol. 97 (1991) 1588–1591. [PMID: 16668590]
2.  Silver, G.M. and Fall, R. Characterization of aspen isoprene synthase, an enzyme responsible for leaf isoprene emission to the atmosphere. J. Biol. Chem. 270 (1995) 13010–13016. [PMID: 7768893]
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[EC 4.2.3.27 created 2007]
 
 


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