Studies in the mechanism of enzyme action. I.—Rôle of the reaction of the medium in fixing the optimum temperature of a ferment

Previously, it has been shown for the enzyme maltase —enzyme requiring an acid medium in which to act to best advantage—that increase in the acidity or hydrogen ion concentration of the medium in which the enzyme acts, beyond the optimum acidity, leads to a fall of optimum temperature. The mechanism of his temperature of this temperature effect appears clearly to be due to a certain disablement of the enzyme activity, estimated at the optimum temperature point; which decrease of activity is itself a function of the degree of acidity of the medium in excess of that necessary to produce optimum activation. Being in this way a disablement effect, the question arises whether, by adding to the quantity of enzyme in action, the lowering of optimum temperature which takes place can be controlled. To answer that question, the experiments described in the present paper were undertaken. For the investigation, the enzyme used is the maltase of Aspergillus oryzœ , the same preparation being employed as studied by us in two previous communications, a specially active specimen of takadiastase, purified by repeated solution in water and reprecipitation by alcohol.