Cobalamin reduction by dithionite. Evidence for the formation of a six-coordinate cobalamin(ii) complex

摘要

Evidence for the formation of a unique, six-coordinate cobalamin(ii) complex with the anion-radical SO_2~- during the reduction of aquacobalamin(iii) by sodium dithionite, was obtained from spectrophotometric and EPR measurements. The pK_a value of the weakly coordinated dimethylbenzimidazole group was found to be 4.8 ± 0.1 at 25 °C.