title: Reductive activation of the methyl coenzyme M methylreductase system of Methanobacterium thermoautotrophicum delta H.
abstract: When titanium(III) citrate was used as electron donor for the reduction of methyl coenzyme M by the methyl coenzyme M methylreductase system of Methanobacterium thermoautotrophicum delta H, component A1 was no longer required. The simpler system thus obtained required components A2, A3, and C as well as catalytic amounts of ATP, vitamin B12, and the disulfide of 7-mercaptoheptanoylthreonine phosphate in addition to titanium(III) citrate. This three component enzyme system also could produce CH4 when stoichiometric amounts of 7-mercaptoheptanoylthreonine phosphate were used as a source of electrons under an H2 atmosphere. When 7-mercaptoheptanoylthreonine phosphate or H2 was used alone no CH4 was produced, indicating a dual requirement for reducing equivalents: one to activate the methylreductase system and the other to reduce methyl coenzyme M. This is the first evidence that the activation of methyl coenzyme M methylreductase is a reductive process.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D002951:Citrates / Q000378:metabolism; D019343:Citric Acid; D004583:Electrons; D019605:Euryarchaeota / Q000201:enzymology*; D015080:Mesna / Q000031:analogs & derivatives / Q000378:metabolism; D008697:Methane / Q000096:biosynthesis; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D014805:Vitamin B 12 / Q000378:metabolism
chemical_list: D002951:Citrates; D019343:Citric Acid; C023349:methyl coenzyme M; D000255:Adenosine Triphosphate; D010088:Oxidoreductases; C021572:methyl coenzyme M reductase; D015080:Mesna; D008697:Methane; D014805:Vitamin B 12