title: On the role of N-7-mercaptoheptanoyl-O-phospho-L-threonine (component B) in the enzymatic reduction of methyl-coenzyme M to methane.
abstract: The reduction of methyl-coenzyme M (CH3SCoM) to methane in methanogenic bacteria is dependent on component B (N-7-mercaptoheptanoyl-O-phospho-L-threonine, HSHTP). We report here that S-methyl-component B (N-7-(methylthio)heptanoyl-O-phospho-L-threonine, CH3SHTP) can substitute for neither CH3SCoM nor HSHTP in the methyl-CoM reductase reaction. Rather, CH3SHTP proved to be an inhibitor competitive with HSHTP (apparent Ki = 6 microM) and noncompetitive with CH3SCoM. These results make it very unlikely that HSHTP functions as a methyl group carrier. A role for HSHTP as direct electron donor for CH3SCoM reduction to CH4 is proposed.
mesh_terms: D002849:Chromatography, Gas; D019605:Euryarchaeota / Q000378:metabolism*; D008623:Mercaptoethanol / Q000031:analogs & derivatives*; D015080:Mesna / Q000031:analogs & derivatives* / Q000378:metabolism; D008697:Methane / Q000096:biosynthesis*; D010088:Oxidoreductases / Q000378:metabolism; D010769:Phosphothreonine / Q000031:analogs & derivatives* / Q000378:metabolism; D013912:Threonine / Q000031:analogs & derivatives*
chemical_list: C049349:7-mercaptoheptanoylthreonine phosphate; D010769:Phosphothreonine; D013912:Threonine; C023349:methyl coenzyme M; D008623:Mercaptoethanol; D010088:Oxidoreductases; C023895:methyl coenzyme M methylreductase; D015080:Mesna; D008697:Methane