Studies on Xanthine Oxidase

IN the previous paper we have described a method for obtaining a preparation of the xanthine oxidase in a form suitable for investigation.While a large amount of work on various enzymes has been done, it appears that the thorough systematic investigation of the dynamics of any one oxidase has not been attempted.The chief difficulty in such work is that of obtaining the enzyme in question free from other enzymes and from oxidisable substances.The above-mentioned preparation is satisfactory in this respect and we there- fore have employed it in investigating the xanthine oxidase.The methylene blue technique was used throughout.The reduction velocity-time curve of the reaction with methylene blue was not investigated by Morgan, Stewart and Hopkins 1922, but they believed that the velocity was constant during the course of the reduction.This has been verified by the use of a modification of the colorimetric method used by Dixon and Tunnicliffe 1923.The amount of methylene blue remain-