Preparation of coenzyme M analogs and their activity in the methyl coenzyme M reductase system of Methanobacterium thermoautotrophicum

A number of 2-(methylthio)ethanesulfonate (methyl-coenzyme M) analogues were synthesized and investigated as substrates for methyl-coenzyme M reductase, an enzyme system found in extracts of Methanobacterterium thermoautotrophicum. Replacement of the methyl moiety by an ethyl group yielded an analogue which served as a precursor for ethane formation. Propyl-coenzyme M, however, was not converted to propane. Analogues which contained additional methylene carbons such as 3-(methylthio)propanesulfonate or 4-(methylthio)butanesulfonate or analogues modified at the sulfide or sulfonate position, N-methyltaurine and 2-(methylthio)ethanol, were inactive. These analogues, in addition to a number of commercially available compounds, also were tested for their ability to inhibit the reduction of methyl-coenzyme M to methane. Bromoethanesulfonate and chloroethanesulfonate proved to be potent inhibitors of the reductase, resulting in 50% inhibition at 7.9 X 10(6) M and 7.5 X 10(5) M. Analogues to coenzyme M which contained modifications to other regions were evaluated also and found to be weak inhibitors of methane biosynthesis.