Mechanism for the interaction of thiols with methylcobalamin

• Published in: Biochimica et biophysica acta Vol. 428; no. 3; pp. 808 - 817
• Main Authors: Frick, T., Francia, Marie D., Wood, J.M.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 28.05.1976
• Subjects: Binding Sites; Disulfides; Glutathione; Magnetic Resonance Spectroscopy; Molecular Conformation; Spectrophotometry; Sulfhydryl Compounds; Vitamin B 12
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/0304-4165(76)90212-9

The reaction between methylcobalamin and ethane-thiol sulfonic acid (Coenzyme 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 σ-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 coordination of thiols to cobalt has previously been reported to occur by a number of of researh groups including our own.