Cawley G F, Batie C J, Backes W L
Department of Pharmacology and Experimental Therapeutics, Louisiana State University Medical Center, New Orleans 70112.
Biochemistry. 1995 Jan 31;34(4):1244-7. doi: 10.1021/bi00004a018.
The goal of these studies was to demonstrate that one P450 isozyme can influence the function of another isozyme when combined in a reconstituted system. Benzphetamine and 7-pentoxyresorufin were both shown to be preferred substrates for P450 2B4 (LM2) as compared to P450 1A2 (LM4). However, these substrates exhibited different characteristics when examined in reconstituted systems containing reductase and both P450 isozymes. Whereas benzphetamine demethylation showed a small increase in catalytic activity when both P450 1A2 and 2B4 were present over the activities obtained in simple reconstituted systems, 7-pentoxyresorufin O-dealkylation (PROD) was dramatically inhibited when both isozymes were present. These results indicate that the functional interactions between P450s in complex reconstituted systems are dependent on the substrate present. Inhibition of PROD was also dependent on reductase levels, with the inhibitory effect being more pronounced at subsaturating reductase. Finally, these protein-protein interactions were shown to be dependent on the reductase concentration in the reconstituted system rather the P450 concentration, supporting the view that P450 1A2 is inhibiting the reaction by competing with P450 2B4 for reductase molecules.
这些研究的目的是证明在重组系统中，一种细胞色素P450同工酶与另一种同工酶结合时能够影响其功能。与细胞色素P450 1A2（LM4）相比，苄非他明和7-戊氧基试卤灵均被证明是细胞色素P450 2B4（LM2）的首选底物。然而，在含有还原酶和两种细胞色素P450同工酶的重组系统中检测时，这些底物表现出不同的特性。当细胞色素P450 1A2和2B4同时存在时，苄非他明去甲基化的催化活性相较于简单重组系统中的活性略有增加，而当两种同工酶同时存在时，7-戊氧基试卤灵O-脱烷基化（PROD）则受到显著抑制。这些结果表明，复杂重组系统中细胞色素P450之间的功能相互作用取决于所存在的底物。PROD的抑制也取决于还原酶水平，在还原酶亚饱和时抑制作用更为明显。最后，这些蛋白质-蛋白质相互作用被证明取决于重组系统中的还原酶浓度而非细胞色素P450浓度，这支持了细胞色素P450 1A2通过与细胞色素P450 2B4竞争还原酶分子来抑制反应的观点。
