Methylcobalamin: Methylation of platinum and demethylation with lead

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Abstract
Aerobic incubation of μM levels of K2PtCl6 and methylcobalamin (MeB‐12) at pH 2.0 (0.01 M HC1) results in the complete conversion of MeB‐12 to aquoB‐12 without the accumulation of any corrinoid intermediates. Platinic sulfate (Pt(SO4)2) is also reactive; whereas, K2PtCl4 alone is unreactive. Soluble lead salts containing Pb2+ were likewise inactive; however, partial to complete demethylation was observed by prolonged incubation with fine suspensions of Pb4+ compounds. Demethylation of [Me‐14C]MeB‐12 with Pb4+ oxides was accompanied by a proportionate volatilization of the label and only unreacted radioactive MeB‐12 was detected upon paper electrophoresis. In contrast, demethylation with K2PtCl6 occurs with a high recovery of nonvolatile 14C which migrates with a major zone of Pt upon electrophoresis. There is no selective loss of 3H when [Me‐3H]MeB‐12 reacts with K2PtCl6. The Me‐Pt product has been isolated and characterized with respect to its light absorption spectrum in aqueous solutions.

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