Reaction: 2 S-adenosyl-L-methionine + glycine = 2 S-adenosyl-L-homocysteine + N,N-dimethylglycine (overall reaction)
(1a) S-adenosyl-L-methionine + glycine = S-adenosyl-L-homocysteine + sarcosine
(ab) S-adenosyl-L-methionine + sarcosine = S-adenosyl-L-homocysteine + N,N-dimethylglycine
Glossary: sarcosine = N-methylglycine
Other name(s): ApGSMT; glycine-sarcosine methyltransferase; GSMT; GMT; glycine sarcosine N-methyltransferase; S-adenosyl-L-methionine:sarcosine N-methyltransferase
Systematic name: S-adenosyl-L-methionine:glycine(or sarcosine) N-methyltransferase [sarcosine(or N,N-dimethylglycine)-forming]
Comments: Cells of the oxygen-evolving halotolerant cyanobacterium Aphanocthece halophytica synthesize betaine from glycine by a three-step methylation process. This is the first enzyme and it leads to the formation of either sarcosine or N,N-dimethylglycine, which is further methylated to yield betaine (N,N,N-trimethylglycine) by the action of EC 2.1.1.157, sarcosine/dimethylglycine N-methyltransferase. Differs from EC 2.1.1.20, glycine N-methyltransferase, as it can further methylate the product of the first reaction. Acetate, dimethylglycine and S-adenosyl-L-homocysteine can inhibit the reaction [3].
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 294210-82-5
References:
1. Nyyssölä, A., Kerovuo, J., Kaukinen, P., von Weymarn, N. and Reinikainen, T. Extreme halophiles synthesize betaine from glycine by methylation. J. Biol. Chem. 275 (2000) 22196-22201. [PMID: 10896953]
2. Nyyssölä, A., Reinikainen, T. and Leisola, M. Characterization of glycine sarcosine N-methyltransferase and sarcosine dimethylglycine N-methyltransferase. Appl. Environ. Microbiol. 67 (2001) 2044-2050. [PMID: 11319079]
3. Waditee, R., Tanaka, Y., Aoki, K., Hibino, T., Jikuya, H., Takano, J., Takabe, T. and Takabe, T. Isolation and functional characterization of N-methyltransferases that catalyze betaine synthesis from glycine in a halotolerant photosynthetic organism Aphanothece halophytica. J. Biol. Chem. 278 (2003) 4932-4942. [PMID: 12466265]