Tetrahydrofolate serves as a methyl acceptor in the demethylation of dimethylsulfoniopropionate in cell extracts of sulfate-reducing bacteria.
Tetrahydrofolate was shown to function as a methyl acceptor in the anaerobic demethylation of dimethylsulfoniopropionate to methylthiopropionate in cell extracts of the sulfate-reducing bacterium strain WN. Dimethylsulfoniopropionate-dependent activities were 0.56 micromol methyltetrahydrofolate min-1 (mg protein)-1 and were higher than required to explain the growth rate of strain WN on dimethylsulfoniopropionate. The reaction did not require ATP or reductive activation by titanium(III)-nitrilotriacetic acid. Preincubation of the extract under air significantly decreased the activity (35% loss in 3 h). Three other dimethylsulfoniopropionate-demethylating sulfate reducers, Desulfobacterium niacini, Desulfobacterium vacuolatum, and Desulfobacterium strain PM4, had dimethylsulfoniopropionate:tetrahydrofolate methyltransferase activities of 0.16, 0.05, and 0.24 micromol min-1 (mg protein)-1, respectively. No methyltransferase activity to tetrahydrofolate was found with betaine as a substrate, not even in extracts of betaine-grown cells of these sulfate reducers. Dimethylsulfoniopropionate demethylation in cell extracts of strain WN was completely inhibited by 0.5 mM propyl iodide; in the light, the inhibition was far less strong, indicating involvement of a corrinoid-dependent methyltransferase.
Jansen
M
M
Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, NL-9751 NN Haren, The Netherlands.
Hansen
T A
TA
D001673:Biodegradation, Environmental; D008780:Methyltransferases / Q000378:metabolism; D013452:Sulfonium Compounds / Q000378:metabolism*; D016999:Sulfur-Reducing Bacteria / Q000201:enzymology / Q000378:metabolism*; D013763:Tetrahydrofolates / Q000378:metabolism*
D013452:Sulfonium Compounds; D013763:Tetrahydrofolates; C030371:5,6,7,8-tetrahydrofolic acid; C068078:dimethylpropiothetin; D008780:Methyltransferases