On the Metabolism of Organic Acids by Clostridium acetobutylicum

Part IV. Mechanism of Racemiase Action

抄録

The mechanism of racemization of optically active lactic acid by racemiase of Clostridium acetobutylicum was investigated. Pyruvic acid and enol-lactic acid were excluded from the possible intermediate of racemiase action. Among four radicals of lactic acid, that is methyl, hydrogen, hydroxyl and carboxyl radicals, hydroxyl radical was pointed out to be essential for the enzymatic reaction. Finally, acrylic acid (dehydrated form of lactic acid) was suggested as the intermediate. The role of coenzymic substances, both pyridoxamine phosphate and ferrous ion, was investigated using the non-ellzymatic racemization of lactic acid in the system including optically active lactic acid, pyridoxamine and ferrous sulphate. In this paper, it was proposed that a complex consisting of acrylic acid, pyridoxamine phosphate, ferrous ion and aporacemiase would be intermediary in racemiase reaction of this organism.