Glycine/sarcosine N-methyltransferase (EC 2.1.1.156, ApGSMT, glycine-sarcosine methyltransferase, GSMT, GMT, glycine sarcosine N-methyltransferase, S-adenosyl-L-methionine:sarcosine N-methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:glycine(or sarcosine) N-methyltransferase (sarcosine(or N,N-dimethylglycine)-forming).^[1][2][3] This enzyme catalyses the following chemical reaction

2 S-adenosyl-L-methionine + glycine ${\displaystyle \rightleftharpoons }$ 2 S-adenosyl-L-homocysteine + N,N-dimethylglycine (overall reaction)

(1a) S-adenosyl-L-methionine + glycine ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + sarcosine

(1b) S-adenosyl-L-methionine + sarcosine ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + N,N-dimethylglycine

This enzyme participates in biosynthesis of betaine from glycine in cyanobacterium Aphanocthece halophytica.

• Glycine/sarcosine+N-methyltransferase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)