Metabolism of diphenyloxazole (PPO) by mouse liver microsomes.

2, 5-Diphenyloxazole (PPO) is an inducer and inhibitor of aryl hydrocarbon hydroxylase. We report that PPO is itself metabolized to an alkali-extractable metabolite with intense fluorescence. The fluorescence spectra of excitation and emission indicate peaks at 345 nm and 510 nm, respectively. The reaction is linear with respect to time and enzyme concentration. NADPH is required for activity and the reaction is inhibited by carbon monoxide and 7, 8-benzoflavone but not by SKF-525A or hexobarbital. The intensity of fluorescence produced is similar to that of benzo (a) pyrene. PPO may be a useful model compound in studies of drug metabolism by the mixed function oxidase.