EC 2.8.4.1; coenzyme-B sulfoethylthiotransferase; a nickel-containing enzyme that catalyses the methane-releasing reaction in methanogenic bacteria. Severe enzyme deficiency from many mutations leads to developmental delay, seizures, and psychiatric manifestations, hyperhomocystinemia and homocystinuria, premature atherosclerosis, and demyelination. See factor F430.