Studies on xanthine oxidase. X

Abstract

Visible light markedly affected the rate of reduction of methylene blue by hypoxanthine with xanthine oxidase obtained from milk, but- only when O was present in the solutions during the exposure. Evidence is submitted to show that these effects are due to the formation of H2O2 by the action of the light on the dye in solution. When the peroxide formed is small in amount in comparison to the oxidase present, its activity in reducing the dye is increased, but if enough is formed the oxidase will be destroyed. All these effects can be duplicated in the absence of light by adding H2O2 to the solutions.