The Enzyme Database

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EC 1.14.14.42     
Accepted name: homomethionine N-monooxygenase
Reaction: an L-polyhomomethionine + 2 [reduced NADPH—hemoprotein reductase] + 2 O2 = an (E)-ω-(methylsulfanyl)alkanal oxime + 2 [oxidized NADPH—hemoprotein reductase] + CO2 + 3 H2O (overall reaction)
(1a) an L-polyhomomethionine + [reduced NADPH—hemoprotein reductase] + O2 = an L-N-hydroxypolyhomomethionine + [oxidized NADPH—hemoprotein reductase] + H2O
(1b) an L-N-hydroxypolyhomomethionine + [reduced NADPH—hemoprotein reductase] + O2 = an L-N,N-dihydroxypolyhomomethionine + [oxidized NADPH—hemoprotein reductase] + H2O
(1c) an L-N,N-dihydroxypolyhomomethionine = an (E)-ω-(methylsulfanyl)alkanal oxime + CO2 + H2O
Glossary: homomethionine = (2S)-2-amino-5-(methylsulfanyl)pentanoate
an L-polyhomomethionine = analogs of L-methionine that contain additional methylene groups in the side chain prior to the sulfur atom.
Other name(s): CYP79F1 (gene name); CYP79F2 (gene name)
Systematic name: L-polyhomomethionine,[NADPH—hemoprotein reductase]:oxygen oxidoreductase
Comments: This plant cytochrome P-450 (heme thiolate) enzyme is involved in methionine-derived aliphatic glucosinolates biosynthesis. It catalyses two successive N-hydroxylations, which are followed by dehydration and decarboxylation. CYP79F1 from Arabidopsis thaliana can metabolize mono-, di-, tri-, tetra-, penta-, and hexahomomethionine to their corresponding aldoximes, while CYP79F2 from the same plant can only metabolize penta- and hexahomomethionine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Hansen, C.H., Wittstock, U., Olsen, C.E., Hick, A.J., Pickett, J.A. and Halkier, B.A. Cytochrome p450 CYP79F1 from arabidopsis catalyzes the conversion of dihomomethionine and trihomomethionine to the corresponding aldoximes in the biosynthesis of aliphatic glucosinolates. J. Biol. Chem. 276 (2001) 11078–11085. [DOI] [PMID: 11133994]
2.  Chen, S., Glawischnig, E., Jørgensen, K., Naur, P., Jorgensen, B., Olsen, C.E., Hansen, C.H., Rasmussen, H., Pickett, J.A. and Halkier, B.A. CYP79F1 and CYP79F2 have distinct functions in the biosynthesis of aliphatic glucosinolates in Arabidopsis. Plant J. 33 (2003) 923–937. [DOI] [PMID: 12609033]
[EC 1.14.14.42 created 2017]
 
 
EC 2.3.3.17     
Accepted name: methylthioalkylmalate synthase
Reaction: an ω-(methylsulfanyl)-2-oxoalkanoate + acetyl-CoA + H2O = a 2-[ω-(methylsulfanyl)alkyl]malate + CoA
For diagram of L-Homomethionine biosynthesis, click here
Other name(s): MAM1 (gene name); MAM3 (gene name); acetyl-CoA:ω-(methylthio)-2-oxoalkanoate C-acetyltransferase
Systematic name: acetyl-CoA:ω-(methylsulfanyl)-2-oxoalkanoate C-acetyltransferase
Comments: The enzyme, characterized from the plant Arabidopsis thaliana, is involved in the L-methionine side-chain elongation pathway, forming substrates for the biosynthesis of aliphatic glucosinolates. Two forms are known - MAM1 catalyses only only the first two rounds of methionine chain elongation, while MAM3 catalyses all six cycles, up to formation of L-hexahomomethionine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Textor, S., Bartram, S., Kroymann, J., Falk, K.L., Hick, A., Pickett, J.A. and Gershenzon, J. Biosynthesis of methionine-derived glucosinolates in Arabidopsis thaliana: recombinant expression and characterization of methylthioalkylmalate synthase, the condensing enzyme of the chain-elongation cycle. Planta 218 (2004) 1026–1035. [DOI] [PMID: 14740211]
2.  Textor, S., de Kraker, J.W., Hause, B., Gershenzon, J. and Tokuhisa, J.G. MAM3 catalyzes the formation of all aliphatic glucosinolate chain lengths in Arabidopsis. Plant Physiol. 144 (2007) 60–71. [DOI] [PMID: 17369439]
[EC 2.3.3.17 created 2016]
 
 
EC 4.2.1.170     
Accepted name: 2-(ω-methylthio)alkylmalate dehydratase
Reaction: (1) a 2-[(ω-methylsulfanyl)alkyl]malate = a 2-[(ω-methylsulfanyl)alkyl]maleate + H2O
(2) a 3-[(ω-methylsulfanyl)alkyl]malate = a 2-[(ω-methylsulfanyl)alkyl]maleate + H2O
For diagram of L-Homomethionine biosynthesis, click here
Other name(s): IPMI (gene name); 2-[(ω-methylthio)alkyl]malate hydro-lyase (2-[(ω-methylthio)alkyl]maleate-forming)
Systematic name: 2-[(ω-methylsulfanyl)alkyl]malate hydro-lyase (2-[(ω-methylsulfanyl)alkyl]maleate-forming)
Comments: The enzyme, characterized from the plant Arabidopsis thaliana, is involved in the L-methionine side-chain elongation pathway, forming substrates for the biosynthesis of aliphatic glucosinolates. By catalysing a dehydration of a 2-[(ω-methylsulfanyl)alkyl]maleate, followed by a hydration at a different position, the enzyme achieves the isomerization of its substrates. The enzyme is a heterodimer comprising a large and a small subunits. The large subunit can also bind to an alternative small subunit, forming EC 4.2.1.33, 3-isopropylmalate dehydratase, which participates in L-leucine biosynthesis.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Knill, T., Reichelt, M., Paetz, C., Gershenzon, J. and Binder, S. Arabidopsis thaliana encodes a bacterial-type heterodimeric isopropylmalate isomerase involved in both Leu biosynthesis and the Met chain elongation pathway of glucosinolate formation. Plant Mol. Biol. 71 (2009) 227–239. [DOI] [PMID: 19597944]
[EC 4.2.1.170 created 2016]
 
 


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