Characterization of glycine sarcosine N-methyltransferase and sarcosine dimethylglycine N-methyltransferase

Antti Nyyssölä (Corresponding Author), Tapani Reinikainen, Matti Leisola

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Glycine betaine is accumulated in cells living in high salt concentrations to balance the osmotic pressure. Glycine sarcosine N-methyltransferase (GSMT) and sarcosine dimethylglycine N-methyltransferase (SDMT) of Ectothiorhodospira halochloris catalyze the threefold methylation of glycine to betaine, with S-adenosylmethionine acting as the methyl group donor. These methyltransferases were expressed in Escherichia coli and purified, and some of their enzymatic properties were characterized. Both enzymes had high substrate specificities and pH optima near the physiological pH. No evidence of cofactors was found. The enzymes showed Michaelis-Menten kinetics for their substrates. The apparent Km and Vmax values were determined for all substrates when the other substrate was present in saturating concentrations. Both enzymes were strongly inhibited by the reaction product S-adenosylhomocysteine. Betaine inhibited the methylation reactions only at high concentrations.
Original languageEnglish
Pages (from-to)2044-2050
Number of pages7
JournalApplied and Environmental Microbiology
Issue number5
Publication statusPublished - 2001
MoE publication typeA1 Journal article-refereed


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