Generation of superoxide radical during autoxidation of hydroxylamine and an assay for superoxide dismutase.

Accompanying the autoxidation of hydroxylamine at pH 10.2, nitroblue tetrazolium was reduced and nitrite was produced in the presence of EDTA. The rate of at&oxidation was negligible below pH 8.0, but sharply increased with increasing pH. The reduction of nitroblue tetrazolium was inhibited by euperoxide dismutaee, indicating the participation of superoxide anion radical in the autoxidation. Hydrogen peroxide stimulated the autoxidation and superoxide diemutase inhibited the hydrogen peroxide-induced oxidation, results which suggest the participation of hydrogen peroxide in autoxidation and in the generation of superoxide radical. An assay for superoxide dismutase using autoxidation of hydroxylamine is described.