The involvement of superoxide anions in the autoxidation of various cofactors of cysteamine-oxygenase

The reduction of tetranitroblue tetrazolium with cysteamine, mediated by a number of dyes, elemental sulphur, elemental selenium and selenide, under aerobic conditions, was inhibited to various extent upon addition of superoxide dismutase. A strict parallelism between the ability to produce O2- ions and the property of those compounds to act as cofactors for cysteamine-oxygenase, to yield hypotaurine, has been observed. Based on the fact that the autoxidation of cysteamine also gives rise to O2- formation, though to a minor extent, we propose a mechanism for cysteamine-oxygenase action. This mechanism was derived from the data obtained in the model system studied.