S-methyl glutathione synthesis is catalyzed by the cheR methyltransferase in Escherichia coli.

The cheR methyltransferase, known to be necessary for the methyl esterification of receptors involved in chemotaxis, is shown to be essential to the synthesis of S-methyl glutathione from glutathione and S-adenosylmethionine in intact Escherichia coli. S-Methyl glutathione is not, however, found to be essential for chemotaxis. It is suggested that the synthesis of S-methyl glutathione may be due to a "parasitic" reaction of glutathione with S-adenosylmethionine bound to the methyltransferase.