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Abstract
Racemiase, an enzyme which catalyzed racemization of lactic acids, was isolated from culture filtrate of Clostridium acetobutylicum by salting-out, and its purification was attained to about twenty-fold by treating with calcium phosphate gel. It was shown that racemiase requires for its full activity cofactors, pyridoxamine phosphate and ferrous ions. These substances were detected in the racemiasc preparation. Several other properties of racemiase were also investigated.
Abstract
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-enzymatic 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.
Abstract
Pyridoxine analogues promoted the racemiase formation by Clostridium acetobutylicum. This effect was investigated employing culture media supplemented with these analogues. Pyridine, nicotinic acid and niacinamide, meanwhile, showed intensive inhibition on the formation of this enzyme. In these cases, scarcely any variation was detected in the growth of organism and the composition of fermentation products. In the crotonate-added culture. a considerable amount of latic acid accumulated and the formation of racemiase was accelerated remarkably.
Abstract
The molar balance sheet of acetone-butanol fermentation was presented. It was pointed out that crotonic acid, whose derivative (crotonyl-CoA) was presumed to be an intermediate in acetone-butanol fermentation, could be introduced into the fermentation of Clostridium acetobutylicum. By intact cells of this organism, crotonic acid was converted to acetic and butyric acids anaerobically.
Abstract
Molecular hydrogen was capable of generating the reduced coenzymes by the hydrogenase system of Clostridium acetobutylicum. It was pointed out that crotonic acid was activated and reduced quantitatively to butyric acid by intact cells and cell-free preparation of this organism in the presence of acetyl phosphate, 2,3-dimercaptopropanol (BAL) and hydrogen gas.