Biosynthesis of all-trans-retinoic acid from all-trans-retinol: catalysis of all-trans-retinol oxidation by human P-450 cytochromes.

摘要: Oxidative conversion of all-trans-retinol (t-ROH) to all-trans-retinal (t-RAL) is recognized as the rate-limiting step for biosynthesis all-trans-retinoic acid from t-ROH in mammalian hepatic tissues. The purpose this study was investigate role human cytochrome P-450 (CYP)-dependent monooxygenation t-RAL. Adult liver microsomes (HLMS) were incubated with t-ROH, and retinoids generated identified quantified by liquid chromatography-mass spectroscopy, HPLC, other methods. HLMS-catalyzed generation t-RAL primarily NADPH-dependent strongly inhibited carbon monoxide. Rates reactions increased linearly time concentrations HLMS, exhibited classical substrate saturation. These observations indicated that reaction proceeded via CYP-catalyzed monooxygenation. On basis responses selective chemical inhibitors, isoforms CYP family 1 CYP3A subfamily appeared be very active. Members CYP2C CYP2D6 lesser activities CYP2A6, CYP2B6, CYP2E1 virtually inactive. cDNA-expressed enzymes (CYP SUPERSOMES) also used assess capacity individual catalyze reaction. Based on specific activities, levels present adult tissues, CYP1A2 CYP3A4 major catalyzing oxidative liver. CYP1A1 CYP1B1 SUPERSOMES both exceptionally high extrahepatic these could play important roles t-ROH.