EVIDENCE FOR A COMMON SELENOLATE INTERMEDIATE IN THE GLUTATHIONE PEROXIDASE-LIKE CATALYSIS OF ALPHA-(PHENYLSELENENYL) KETONES AND DIPHENYL DISELENIDE

The glutathione peroxidase-like catalysis of alpha-(phenylselenenyl) ketones was investigated. Degradation studies demonstrated the rapid cleavage of the aliphatic carbon-selenium bond of alpha-(phenylselenenyl) ketones by glutathione at pH 6.9 in a methanolic phosphate buffer under argon. On treatment with excess glutathione under aerobic conditions, alpha-(phenylselenenyl) ketones, S-(phenylselenenyl)glutathione and diphenyl diselenide were all shown to give benzeneselenolate. This material was found to be oxidized by hydrogen peroxide considerably faster than alpha-(phenylselenenyl) ketones, S-(phenylselenenyl)glutathione or diphenyl diselenide. A catalytic mechanism involving benzeneselenolate, benzeneselenenic acid and S-(phenylselenenyl)glutathione as cruical intermediates was proposed to account for the glutathione peroxidase-like catalysis of alpha-(phenylselenenyl) ketones and diphenyl diselenide.