Interaction of coenzyme M and formaldehyde in methanogenesis

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Abstract
Chemical reaction of coenzyme M, sodium 2-mercaptoethanesulfonate (HS-CoM, Na+) and formaldehyde formed sodium 2-(hydroxymethylthio)ethanesulfonate (HOCH2-S-CoM), whereas reaction with the ammonium salt of HS-CoM yielded iminobis-[2-(methylthio)ethanesulfonate], monoammonium salt [NH=(CH2-S-CoM)2]. In water, NH=(CH2-S-CoM)2 decomposed to 2-(aminomethylthio)ethane-sulfonate (NH2CH2-S-CoM) and HOCH2-S-CoM. NH2CH2-S-CoM was degraded further to form more HOCH2-S-CoM. The structures of these coenzyme M derivatives were confirmed by IR and NMR spectroscopy and by elemental analysis. When added to cell extracts of Methanobacterium thermoautotrophicum, methane was formed from either HOCH2-S-CoM or NH=(CH2-S-CoM)2 at rates comparable with the rate of methane formation from the methanogenic precursor 2-(methylthio)ethanesulfonate (CH3-S-CoM). Formaldehyde was reduced to methane at similar rates. Certain hemimercaptals, including thiazolidine and thiazolidine-4-carboxylate, were reduced, although at slower rates. The reduction of formaldehyde, thiazolidine or thiazolidine-4-carboxylate required catalytic amounts of HS-CoM. ATP was required by cell extracts for reduction of each of these methane precursors.