IUBMB Enzyme Nomenclature


Accepted name: homocysteine S-methyltransferase

Reaction: S-methyl-L-methionine + L-homocysteine = 2 L-methionine

Other name(s): S-adenosylmethionine homocysteine transmethylase; S-methylmethionine homocysteine transmethylase; adenosylmethionine transmethylase; methylmethionine:homocysteine methyltransferase; adenosylmethionine:homocysteine methyltransferase; homocysteine methylase; homocysteine methyltransferase; homocysteine transmethylase; L-homocysteine S-methyltransferase; S-adenosyl-L-methionine:L-homocysteine methyltransferase; S-adenosylmethionine-homocysteine transmethylase; S-adenosylmethionine:homocysteine methyltransferase

Systematic name: S-methyl-L-methionine:L-homocysteine S-methyltransferase

Comments: The enzyme uses S-adenosyl-L-methionine as methyl donor less actively than S-methyl-L-methionine.

Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, PDB, CAS registry number: 9012-40-2


1. Balish, E. and Shapiro, S.K. Methionine biosynthesis in Escherichia coli: induction and repression of methylmethionine (or adenosylmethionine):homocysteine methyltransferase. Arch. Biochem. Biophys. 119 (1967) 62-68. [PMID: 4861151]

2. Shapiro, S.K. Adenosylmethionine-homocysteine transmethylase. Biochim. Biophys. Acta 29 (1958) 405-409. [PMID: 13572358]

3. Shapiro, S.K. and Yphantis, D.A. Assay of S-methylmethionine and S-adenosylmethionine homocysteine transmethylases. Biochim. Biophys. Acta 36 (1959) 241-244. [PMID: 14445542]

4. Mudd, S.H. and Datko, A.H. The S-Methylmethionine Cycle in Lemna paucicostata. Plant Physiol. 93 (1990) 623-630. [PMID: 16667513]

5. Ranocha, P., McNeil, S.D., Ziemak, M.J., Li, C., Tarczynski, M.C. and Hanson, A.D. The S-methylmethionine cycle in angiosperms: ubiquity, antiquity and activity. Plant J. 25 (2001) 575-584. [PMID: 11309147]

6. Ranocha, P., Bourgis, F., Ziemak, M.J., Rhodes, D., Gage, D.A. and Hanson, A.D. Characterization and functional expression of cDNAs encoding methionine-sensitive and -insensitive homocysteine S-methyltransferases from Arabidopsis. J. Biol. Chem. 275 (2000) 15962-15968. [PMID: 10747987]

7. Grue-Sorensen, G., Kelstrup, E., Kjaer, A. and Madsen, J.O.: Diastereospecific, enzymically catalysed transmethylation from S-methylL-L-methionine to L-homocysteine, a naturally occurring process. J. Chem. Soc. Perkin Trans. 1 (1984) 1091-1097.

[EC created 1965, modified 2010]

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