title: Coupling of methyl coenzyme M reduction with carbon dioxide activation in extracts of Methanobacterium thermoautotrophicum.
abstract: The stimulation of carbon dioxide reduction to methane by addition of 2-(methylthio)ethanesulfonate (CH3-S-CoM) to cell extracts of Methanobacterium thermoautotrophicum was investigated. Similar stimulation of CO2 reduction by CH3-S-CoM was found for cell extracts of Methanobacterium bryantii and Methanospirillum hungatei. The CH3-S-CoM requirement could be met by the methanogenic precursors formaldehyde, serine, or pyruvate, or by 2-(ethylthio)ethanesulfonate (CH3CH2-S-CoM), but not by other coenzyme M derivatives. Efficient reduction of CO2 to CH4 was favored by low concentrations of CH3-S-CoM and high concentrations of CO2. Sulfhydryl compounds were identified as effective inhibitors of CO2 reduction. Both an allosteric model and a free-radical model for the mechanism of CO2 activation and reduction are discussed.
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D019605:Euryarchaeota / Q000378:metabolism*; D007700:Kinetics; D008623:Mercaptoethanol / Q000031:analogs & derivatives*; D015080:Mesna / Q000031:analogs & derivatives* / Q000378:metabolism; D010084:Oxidation-Reduction; D013045:Species Specificity
chemical_list: D002245:Carbon Dioxide; C023349:methyl coenzyme M; D008623:Mercaptoethanol; D015080:Mesna