A study of the binding of sulfur to rat liver microsomes which occurs concurrently with the metabolism of O, O-diethyl O-p-nitrophenyl phosphorothioate (parathion) to O, O-diethyl O-p-nitrophenyl phosphate (paraoxon).

In order to investigate the nature of the sulfur that is bound to liver microsomes concurrently with the metabolism of parathion to paraoxon, an isolated rat liver microsomal preparation was labeled with [35S] parathion and the purified product was examined by chemical degradation. Characterization of the degradation products by thin-layer chromatography indicated that the sulfur is bound as a polysulfide or hydrodisulfide formed by the combination of a reactive form of sulfur, released from parathion, with cysteine residues of the microsomal protein. Preliminary investigations revealed similar binding occurs when the microsomal preparation is replaced with purified rabbit cytochrome P-450 plus NADPH-cytochrome P-450 reductase and NADPH.