Preparation and Properties of Trimethylsulfonium-Tetrahydrofolate Methyltransferase

An enzyme that catalyzes the transfer of a methyl group from trimethylsulfonium chloride to tetrahydrofolate has been isolated from a species of Pseudomonas. This enzyme has been partially purified and several of its properties have been studied. The reaction can be formulated as a simple methyl transfer, with the formation of dimethyl sulfide and 5-methyltetrahydrofolate. Neither S-adenosylmethionine nor dimethyl-β-propiothetin can replace trimethylsulfonium chloride as methyl donor. 2-Mercaptoethanol is unable to replace tetrahydrofolate as methyl acceptor. The enzyme has a molecular weight of approximately 100,000. There is no vitamin B12 derivative associated with the enzyme.