Studies on enzyme action. XXIII.—Homo- and Hetero-lytic enzymes

Abstract

From the evidence given by Prof. Hopkins and his co-workers, it is clear that the agent in milk which induces the oxidation of both xanthin and hypoxanthin, in presence of either methylene blue or oxygen, is a catalyst , in the sense defined by my son and myself and justified by his later observations on the hydrogenation of oils in presence of nickel: as the change proceeds at the linear rates characteristic of catalytic action, when unhampered by secondary effects. Moreover, the catalyst is so selective in its action, that we are justified in regarding it as an enzyme: an enzyme being a colloid, selective catalyst. The most remarkable result of the inquiry is the establishment of the fact, that the two bases are “hydroxylated” at molecularly equal rates, although twice the work is done upon the one as upon the other. The following may be put forward as perhaps not too daring an explanation of this novel observation.