The Effect of Cyanide on the Schardinger Enzyme

claims to have brought forward evidence that in the aerobic oxidation of aldehydes under the influence of the aldehyde oxidase of milk (Schardinger's enzyme) an activation of the molecular oxygen by iron in accordance with Warburg's theory is necessary. His evidence consists in the observation that cyanide in a concentration of M/200 produced a 75 % inhibition of the uptake of oxygen by the enzyme-aldehyde system, and he concludes that the cyanide acts by inactivating the iron, as it does in the cases of iron catalysis studied by Warburg and others. The question is of importance in connection with Warburg's theory of tissue oxidations, and in view of the facts that Dixon and Thurlow [1925] have shown that the xanthine oxidase system is independent of such activation by iron, and have further shown [1924, 2] that the xanthine oxidase is identical with, or at any rate very closely similar to, the Schardinger enzyme, it was clear that a more detailed study of the action of cyanides on the latter enzyme should be made.