Abstract
The mechanism of the reaction between formic acid and aquocobalamin (OH-B_<12>) was investigated. When formic acid and OH-B_<12> were incubated in acetate buffer (pH 5) under aerobic conditions at 37℃, carbon dioxide evolution accompanied by oxygen consumption was observed. It was found that 1 mole of OH-B_<12> decarboxylated 20 moles of formic acid. The result of spectrophotometric observation indicated that reduced cobalamin, B_<12r>, is formed as catalytic intermediate in the decarboxylation of formic acid. From these results, it was confirmed that the oxidative decarboxylation of formic acid was catalyzed by traces of OH-B_<12>. The catalytic activity of cobalamin analogs decreased in the order of OH-B_<12>>hydroxocobinamide>DBCC, cyanocobalamin, cyanocobinamide. The mechanism of the catalytic reaction was discussed.
