Studies on the Coordination of Reduced Gluthathione to B12 Coenzymes

Ping-Yee Law, J. M. Wood

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Reduced glutathione coordinates (S bonded) to cobalt in 5 ′-deoxyadenosylcobalamin at pH 7.4 and in methylcobalamin at pH 4.0 by displacing the 5,6-dimethylbenzimidazole group from the sixth coordination site. Uv-visible spectral studies, photolability, and pH optima for these two glutathione complexes with B12 confirm that 5,6-dimethylbenzimidazole has been displaced by reduced glutathione. The Co-Cσ bond in the two coenzymes is much less stable to light when glutathione is coordinated in place of 5,6-dimethylbenzimidazole. Electron spin resonance spectra of the reduced glutathione-5′-deoxyadenosylcobalamin complex and the diaquocobinamide-reduced glutathione complex were compared after photolysis under anaerobic conditions. The results from this experiment show that reduced glutathione does not form a stable complex with Co2+, and after quantitative homolysis of the Co-C σbond, then 5,6-dimethylbenzimidazole recoordinates to Co2+ in place of reduced glutathione.

Original languageEnglish (US)
Pages (from-to)914-919
Number of pages6
JournalJournal of the American Chemical Society
Issue number3
StatePublished - Feb 1 1973


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