Quantitative analysis by the oxygen electrode method of superoxide and hydrogen peroxide generated by xanthine oxidase reaction

Abstract

Oxygen consumption and generation of superoxide and hydrogen peroxide by the xanthine oxidase reaction were measured by the polarographic oxygen electrode method. This method requires only a simple apparatus, is very accurate and is easy to perform. The Km for oxygen in the xanthine oxidase reaction measured by this method was 2.1×10^-5M, which is similar to values measured by other methods. Kinetic analyses of superoxide and hydrogen peroxide generation were made by the addition of superoxide dismutase or cytochrome c before the reaction and catalase after the reaction. More than 13% of the oxygen consumed by the addition of xanthine was found to be converted to superoxide, and 70% was converted to hydrogen peroxide in this system. This method was found to be easy to calibrate the rapid xanthine oxidase reaction and to measure the oxygen consumption and generation of superoxide and hydrogen peroxide.