Schelin C, Wallin H, Halpert J, Jergil B
Chem Biol Interact. 1984 May;49(3):269-81. doi: 10.1016/0009-2797(84)90102-9.
A reconstituted mixed-function oxidase system, containing the major beta-naphthoflavone-induced isozyme of rat liver cytochrome P-450 bound benzo[a]pyrene covalently in the presence of NADPH. NADPH-cytochrome P-450 reductase was required for binding and a maximum rate of adduct formation was obtained at 8 units of reductase per nmol cytochrome P-450. Phosphatidylcholine inhibited this reaction. Benzo[a]pyrene was bound to the cytochrome, but not to the reductase, as shown by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. Approximately 6 molecules of benzo[a]pyrene bound to each molecule cytochrome P-450 during prolonged incubations. No binding occurred when the beta-naphthoflavone-induced isozyme of cytochrome P-450 was replaced by the major isozyme induced by phenobarbital, but both cytochromes incorporated benzo[a]pyrene to approximately the same extent when they were incubated together in the presence of the reductase and NADPH. Metabolically activated benzo[a]pyrene also bound covalently to purified epoxide hydrolase, when this enzyme was added to the reconstituted mixed-function oxidase system.
一个重组的混合功能氧化酶系统，在存在NADPH的情况下，包含大鼠肝脏细胞色素P-450的主要β-萘黄酮诱导同工酶，该同工酶与苯并[a]芘共价结合。结合需要NADPH-细胞色素P-450还原酶，每nmol细胞色素P-450有8个还原酶单位时可获得最大加合物形成速率。磷脂酰胆碱抑制此反应。如十二烷基硫酸钠（SDS）-聚丙烯酰胺凝胶电泳所示，苯并[a]芘与细胞色素结合，但不与还原酶结合。长时间孵育期间，每个细胞色素P-450分子约结合6个苯并[a]芘分子。当细胞色素P-450的β-萘黄酮诱导同工酶被苯巴比妥诱导的主要同工酶取代时，不发生结合，但当它们在还原酶和NADPH存在下一起孵育时，两种细胞色素结合苯并[a]芘的程度大致相同。当将纯化的环氧化物水解酶添加到重组的混合功能氧化酶系统中时，代谢活化的苯并[a]芘也与该酶共价结合。
