title: Mechanism for the interaction of thiols with methylcobalamin.
abstract: The reaction between methylcobalamin and ethane-thiol sulfonic acid (Co-enzyme M) has been studied under aerobic conditions. For this reaction evidence is presented for a catalytic cycle which promotes homolytic cleavage of the Cobalt-carbon sigma-bond to give Cob(II)alamin (B12-r) and methylcoenzyme M as the products. This reaction is especially pertinent to our understanding of the mechanism of methane-biosynthesis. In addition, we have used 220 MHZ 1H NMR and 13C NMR to show that thiols do not react with methylcorrinoids by displacing the base trans-axial to the cobalt-carbon bond. This NMR study is especially important since the co-ordination of thiols to cobalt has previously been reported to occur by a number of research groups including our own.
mesh_terms: D001665:Binding Sites; D004220:Disulfides; D005978:Glutathione; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D013053:Spectrophotometry; D013438:Sulfhydryl Compounds; D014805:Vitamin B 12
chemical_list: D004220:Disulfides; D013438:Sulfhydryl Compounds; D005978:Glutathione; D014805:Vitamin B 12