Coenzyme M (CoM)

Coenzyme M is a coenzyme required for methyl-transfer reactions in the metabolism of methanogens. The coenzyme is an anion with the formula HSCH₂CH₂SO₃^-. It is named 2-mercaptoethanesulfonate and abbreviated HS-CoM. The cation is unimportant, but the sodium salt is most available. Mercaptoethanesulfonate contains both a thiol, which is the main site of reactivity, and a sulfonate group, which confers solubility in aqueous media. The coenzyme is the C1 carrier in methanogenesis. It is converted to methyl coenzyme M, the thioether CH₃SCH₂CH₂SO₃^-, in the penultimate step to methane formation. Coenzyme M reacts with coenzyme B, 7-thioheptanoylthreoninephosphate, to give a heterodisulfide, releasing methane: CH₃-S-CoM + HS-CoB → CH₄ + CoB-S-S-CoM

This conversion is catalyzed by the enzyme methyl coenzyme M reductase, which contains cofactor F430 as the prosthetic group.