The reaction of reduced xanthine oxidase with oxygen. Kinetics of peroxide and superoxide formation.

Abstract

Product formation during the oxidation of xanthine oxidase has been examined directly by using cyto- chrome c peroxidase as a trapping agent for hydrogen peroxide and the reduction of cytochrome c as a measure of superoxide formation.When fully reduced enzyme is mixed with high concentrations of oxygen, 2 molecules of HzOz/flavin are produced rapidly, while 1 molecule of (&-/flavin is produced rapidly and another produced much more slowly.Time courses for superoxide formation and those for the absorbance changes due to enzyme oxidation were fitted successfully to the mechanism proposed earlier (Olson, J.