On the role of N‐7‐mercaptoheptanoyl‐O‐phospho‐L‐threonine (component B) in the enzymatic reduction of methyl‐coenzyme M to methane

[摘要]

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 K _i=6 μM) 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 CH₄is proposed.

[学科分类] 生物化学/生物物理

[关键词] Methanogenic bacteria;Methanogenesis;Methyl-CoM reductase;Component B;N-7-Mercaptoheptanoylthreonine phosphate;Coenzyme F430;Vitamin B12;ATP synthesis