The Enzyme Database

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EC 2.1.1.14     
Accepted name: 5-methyltetrahydropteroyltriglutamate—homocysteine S-methyltransferase
Reaction: 5-methyltetrahydropteroyltri-L-glutamate + L-homocysteine = tetrahydropteroyltri-L-glutamate + L-methionine
For diagram of L-Methionine biosynthesis, click here
Other name(s): tetrahydropteroyltriglutamate methyltransferase; homocysteine methylase; methyltransferase, tetrahydropteroylglutamate-homocysteine transmethylase; methyltetrahydropteroylpolyglutamate:homocysteine methyltransferase; cobalamin-independent methionine synthase; methionine synthase (cobalamin-independent); MetE
Systematic name: 5-methyltetrahydropteroyltri-L-glutamate:L-homocysteine S-methyltransferase
Comments: Requires phosphate and contains zinc. The enzyme from Escherichia coli also requires a reducing system. Unlike EC 2.1.1.13, methionine synthase, this enzyme does not contain cobalamin.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9068-29-5
References:
1.  Guest, J.R., Friedman, S., Foster, M.A., Tejerina, G. and Woods, D.D. Transfer of the methyl group from N5-methyltetrahydrofolates to homocysteine in Escherichia coli. Biochem. J. 92 (1964) 497–504. [PMID: 5319972]
2.  Whitfield, C.D., Steers, E.J., Jr. and Weissbach, H. Purification and properties of 5-methyltetrahydropteroyltriglutamate-homocysteine transmethylase. J. Biol. Chem. 245 (1970) 390–401. [PMID: 4904482]
3.  Eichel, J., Gonzalez, J.C., Hotze, M., Matthews, R.G. and Schroder, J. Vitamin B12-independent methionine synthase from a higher-plant (Catharanthus roseus) - molecular characterization, regulation, heterologous expression, and enzyme properties. Eur. J. Biochem. 230 (1995) 1053–1058. [DOI] [PMID: 7601135]
4.  Gonzalez, J.C., Peariso, K., PennerHahn, J.E. and Matthews, R.G. Cobalamin-independent methionine synthase from Escherichia coli: A zinc metalloenzyme. Biochemistry 35 (1996) 12228–12234. [DOI] [PMID: 8823155]
5.  Peariso, K., Goulding, C.W., Huang, S., Matthews, R.G. and Penner-Hahn, J.E. Characterization of the zinc binding site in methionine synthase enzymes of Escherichia coli: The role of zinc in the methylation of homocysteine. J. Am. Chem. Soc. 120 (1998) 8410–8416.
[EC 2.1.1.14 created 1972, modified 2003]
 
 
EC 2.1.1.140     
Accepted name: (S)-coclaurine-N-methyltransferase
Reaction: S-adenosyl-L-methionine + (S)-coclaurine = S-adenosyl-L-homocysteine + (S)-N-methylcoclaurine
For diagram of reticuline-biosynthesis pathway, click here
Systematic name: S-adenosyl-L-methionine:(S)-coclaurine-N-methyltransferase
Comments: The enzyme is specific for the (S)-isomer of coclaurine. Norcoclaurine can also act as an acceptor.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 167398-06-3
References:
1.  Loeffler, S., Deus-Neumann, B. and Zenk, M.H. S-Adenosyl-L-methionine: (S)-coclaurine-N-methyltransferase from Tinospora cordifolia. Phytochemistry 38 (1995) 1387–1395.
[EC 2.1.1.140 created 2001]
 
 
EC 2.1.1.141     
Accepted name: jasmonate O-methyltransferase
Reaction: S-adenosyl-L-methionine + jasmonate = S-adenosyl-L-homocysteine + methyl jasmonate
Glossary: jasmonic acid = {(1R,2R)-3-oxo-2-[(Z)pent-2-enyl]cyclopent-2-enyl}acetic acid
Other name(s): jasmonic acid carboxyl methyltransferase
Systematic name: S-adenosyl-L-methionine:jasmonate O-methyltransferase
Comments: 9,10-Dihydrojasmonic acid is a poor substrate for the enzyme. The enzyme does not convert 12-oxo-phytodienoic acid (a precursor of jasmonic acid), salicylic acid, benzoic acid, linolenic acid or cinnamic acid into their corresponding methyl esters. Enzyme activity is inhibited by the presence of divalent cations, e.g., Ca2+, Cu2+, Mg2+ and Zn2+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 346420-58-4
References:
1.  Seo, H.S., Song, J.T., Cheong, J.J., Lee, Y.H., Lee, Y.W., Hwang, I., Lee, J.S. and Choi, Y.D. Jasmonic acid carboxyl methyltransferase: A key enzyme for jasmonate-regulated plant responses. Proc. Natl. Acad. Sci. USA 98 (2001) 4788–4793. [DOI] [PMID: 11287667]
[EC 2.1.1.141 created 2001]
 
 
EC 2.1.1.142     
Accepted name: cycloartenol 24-C-methyltransferase
Reaction: S-adenosyl-L-methionine + cycloartenol = S-adenosyl-L-homocysteine + (24R)-24-methylcycloart-25-en-3β-ol
For diagram of sterol-sidechain modification, click here
Other name(s): sterol C-methyltransferase
Systematic name: S-adenosyl-L-methionine:cycloartenol 24-C-methyltransferase
Comments: S-Adenosyl-L-methionine methylates the Si face of the 24(25)-double bond with elimination of a hydrogen atom from the pro-Z methyl group at C-25.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 50936-46-4
References:
1.  Mangla, A.T. and Nes, W.D. Sterol C-methyl transferase from Prototheca wickerhamii mechanism, sterol specificity and inhibition. Bioorg. Med. Chem. 8 (2000) 925. [DOI] [PMID: 10882005]
[EC 2.1.1.142 created 2001]
 
 
EC 2.1.1.143     
Accepted name: 24-methylenesterol C-methyltransferase
Reaction: S-adenosyl-L-methionine + 24-methylenelophenol = S-adenosyl-L-homocysteine + (Z)-24-ethylidenelophenol
For diagram of sterol-sidechain modification, click here
Glossary: lophenol = 4α-methyl-5α-cholesta-7-en-3β-ol
Other name(s): SMT2; 24-methylenelophenol C-241-methyltransferase
Systematic name: S-adenosyl-L-methionine:24-methylenelophenol C-methyltransferase
Comments: This is the second methylation step of plant sterol biosynthesis (cf EC 2.1.1.142, cycloartenol 24-C-methyltransferase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 67165-89-3
References:
1.  Bouvier-Navé, P., Husselstein, T. and Benveniste, P. Two families of sterol methyltransferases are involved in the first and the second methylation steps of plant biosynthesis. Eur. J. Biochem. 256 (1998) 88–96. [DOI] [PMID: 9746350]
[EC 2.1.1.143 created 2001]
 
 
EC 2.1.1.144     
Accepted name: trans-aconitate 2-methyltransferase
Reaction: S-adenosyl-L-methionine + trans-aconitate = S-adenosyl-L-homocysteine + (E)-3-(methoxycarbonyl)pent-2-enedioate
For diagram of reaction, click here
Glossary: trans-aconitate = (E)-prop-1-ene-1,2,3-tricarboxylate
Systematic name: S-adenosyl-L-methionine:(E)-prop-1-ene-1,2,3-tricarboxylate 2′-O-methyltransferase
Comments: Also catalyses the formation of the methyl monoester of cis-aconitate, isocitrate and citrate, but more slowly. While the enzyme from Escherichia coli forms (E)-3-(methoxycarbonyl)-pent-2-enedioate as the product, that from Saccharomyces cerevisiae forms (E)-2-(methoxycarbonylmethyl)butenedioate and is therefore classified as a separate enzyme (cf. EC 2.1.1.145, trans-aconitate 3-methyltransferase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 235107-12-7
References:
1.  Cai, H. and Clarke, S. A novel methyltransferase catalyzes the esterification of trans-aconitate in Escherichia coli. J. Biol. Chem. 274 (1999) 13470–13479. [DOI] [PMID: 10224113]
2.  Cai, H., Strouse, J., Dumlao, D., Jung, M.E. and Clarke, S. Distinct reactions catalyzed by bacterial and yeast trans-aconitate methyltransferase. Biochemistry 40 (2001) 2210–2219. [DOI] [PMID: 11329290]
3.  Cai, H., Dumlao, D., Katz, J.E. and Clarke, S. Identification of the gene and characterization of the activity of the trans-aconitate methyltransferase from Saccharomyces cerevisiae. Biochemistry 40 (2001) 13699–13709. [DOI] [PMID: 11695919]
[EC 2.1.1.144 created 2002]
 
 
EC 2.1.1.145     
Accepted name: trans-aconitate 3-methyltransferase
Reaction: S-adenosyl-L-methionine + trans-aconitate = S-adenosyl-L-homocysteine + (E)-2-(methoxycarbonylmethyl)butenedioate
For diagram of reaction, click here
Glossary: trans-aconitate = (E)-prop-1-ene-1,2,3-tricarboxylate
Systematic name: S-adenosyl-L-methionine:(E)-prop-1-ene-1,2,3-tricarboxylate 3′-O-methyltransferase
Comments: Also catalyses the formation of the methyl monoester of cis-aconitate, isocitrate and citrate, but more slowly. While the enzyme from Saccharomyces cerevisiae forms (E)-2-(methoxycarbonylmethyl)butenedioate as the product, that from Escherichia coli forms (E)-3-(methoxycarbonyl)-pent-2-enedioate and is therefore classified as a separate enzyme (cf. EC 2.1.1.144, trans-aconitate 2-methyltransferase)
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 235107-12-7
References:
1.  Cai, H. and Clarke, S. A novel methyltransferase catalyzes the esterification of trans-aconitate in Escherichia coli. J. Biol. Chem. 274 (1999) 13470–13479. [DOI] [PMID: 10224113]
2.  Cai, H., Strouse, J., Dumlao, D., Jung, M.E. and Clarke, S. Distinct reactions catalyzed by bacterial and yeast trans-aconitate methyltransferase. Biochemistry 40 (2001) 2210–2219. [DOI] [PMID: 11329290]
[EC 2.1.1.145 created 2002]
 
 
EC 2.1.1.146     
Accepted name: (iso)eugenol O-methyltransferase
Reaction: S-adenosyl-L-methionine + isoeugenol = S-adenosyl-L-homocysteine + isomethyleugenol
For diagram of reaction, click here
Systematic name: S-adenosyl-L-methionine:isoeugenol O-methyltransferase
Comments: Acts on eugenol and chavicol as well as isoeugenol.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 191744-33-9
References:
1.  Wang, J. and Pichersky, E. Characterization of S-adenosyl-L-methionine:(iso)eugenol O-methyltransferase involved in floral scent production in Clarkia breweri. Arch. Biochem. Biophys. 349 (1998) 153–160. [DOI] [PMID: 9439593]
2.  Gang, D.R., Lavid, N., Zubieta, C., Chen, F., Beuerle, T., Lewinsohn, E., Noel, J.P. and Pichersky, E. Characterization of phenylpropene O-methyltransferases from sweet basil: facile change of substrate specificity and convergent evolution within a plant O-methyltransferase family. Plant Cell 14 (2002) 505–519. [DOI] [PMID: 11884690]
[EC 2.1.1.146 created 2002]
 
 
EC 2.1.1.147     
Accepted name: corydaline synthase
Reaction: S-adenosyl-L-methionine + palmatine + 2 NADPH + H+ = S-adenosyl-L-homocysteine + corydaline + 2 NADP+
For diagram of columbamine, palmatine and corydaline biosynthesis, click here
Systematic name: S-adenosyl-L-methionine:protoberberine 13-C-methyltransferase
Comments: Also acts on 7,8-dihydropalmatine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 155807-67-3
References:
1.  Rueffer, M., Bauer, W. and Zenk, M.H. The formation of corydaline and related alkaloids in Corydalis cava in vivo and in vitro. Canad. J. Chem. 72 (1994) 170–175.
[EC 2.1.1.147 created 2002]
 
 
EC 2.1.1.148     
Accepted name: thymidylate synthase (FAD)
Reaction: 5,10-methylenetetrahydrofolate + dUMP + NADPH + H+ = dTMP + tetrahydrofolate + NADP+
For diagram of C1 metabolism, click here
Other name(s): Thy1; ThyX
Systematic name: 5,10-methylenetetrahydrofolate,FADH2:dUMP C-methyltransferase
Comments: Contains FAD. All thymidylate synthases catalyse a reductive methylation involving the transfer of the methylene group of 5,10-methylenetetrahydrofolate to the C5 position of dUMP and a two electron reduction of the methylene group to a methyl group. Unlike the classical thymidylate synthase, ThyA (EC 2.1.1.45), which uses folate as both a 1-carbon donor and a source of reducing equivalents, this enzyme uses a flavin coenzyme as a source of reducing equivalents, which are derived from NADPH.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 850167-13-4
References:
1.  Myllykallio, H., Lipowski, G., Leduc, D., Filee, J., Forterre, P. and Liebl, U. An alternative flavin-dependent mechanism for thymidylate synthesis. Science 297 (2002) 105–107. [DOI] [PMID: 12029065]
2.  Griffin, J., Roshick, C., Iliffe-Lee, E. and McClarty, G. Catalytic mechanism of Chlamydia trachomatis flavin-dependent thymidylate synthase. J. Biol. Chem. 280 (2005) 5456–5467. [DOI] [PMID: 15591067]
3.  Graziani, S., Bernauer, J., Skouloubris, S., Graille, M., Zhou, C.Z., Marchand, C., Decottignies, P., van Tilbeurgh, H., Myllykallio, H. and Liebl, U. Catalytic mechanism and structure of viral flavin-dependent thymidylate synthase ThyX. J. Biol. Chem. 281 (2006) 24048–24057. [DOI] [PMID: 16707489]
4.  Koehn, E.M., Fleischmann, T., Conrad, J.A., Palfey, B.A., Lesley, S.A., Mathews, I.I. and Kohen, A. An unusual mechanism of thymidylate biosynthesis in organisms containing the thyX gene. Nature 458 (2009) 919–923. [DOI] [PMID: 19370033]
5.  Koehn, E.M. and Kohen, A. Flavin-dependent thymidylate synthase: a novel pathway towards thymine. Arch. Biochem. Biophys. 493 (2010) 96–102. [DOI] [PMID: 19643076]
6.  Mishanina, T.V., Yu, L., Karunaratne, K., Mondal, D., Corcoran, J.M., Choi, M.A. and Kohen, A. An unprecedented mechanism of nucleotide methylation in organisms containing thyX. Science 351 (2016) 507–510. [DOI] [PMID: 26823429]
[EC 2.1.1.148 created 2003, modified 2010]
 
 
EC 2.1.1.149      
Deleted entry: myricetin O-methyltransferase. Now covered by EC 2.1.1.267, flavonoid 3′,5′-methyltransferase.
[EC 2.1.1.149 created 2003, modified 2011, deleted 2013]
 
 


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