Kitada M, Kubota K, Kitagawa H, Kamataki T
Jpn J Pharmacol. 1979 Dec;29(6):877-87. doi: 10.1254/jjp.29.877.
The effects of addition of purified NADPH-cytochrome c (P-450) reductase on microsomal activities of aniline hydroxylation, p-phenetidine O-deethylation and ethylmorphine and aminopyrine N-demethylations were investigated utilizing microsomes from untreated, phenobarbital-treated and 3-methylcholanthrene-treated rats. The purified reductase was incorporated into microsomes. The drug oxidation activities were increased by the fortification of microsomes with the reductase while the extent of increase in the activities varied with the substrate and microsomes employed. The most pronounced enhancement was seen in p-phenetidine O-deethylation, followed by aniline hydroxylation and aminopyrine and ethylmorphine N-demethylations. The enhancement was more remarkable in microsomes from rats treated with 3-methylcholanthrene or phenobarbital. alpha-Naphthoflavone inhibited p-phenetidine O-deethylation activity markedly when the reductase was incorporated into microsomes, indicating that a larger amount of a species of cytochrome P-450 sensitive to the inhibitor was capable of participating in the oxidation of this substrate in the presence of the added reductase. One of the two Km values seen with higher concentrations of aniline or aminopyrine was altered by the fortification of microsomes with the purified NADPH cytochrome c (P-450) reductase. From these results, we propose that NADPH-cytochrome c (P-450) reductase transfers electrons to the selected one or two of multiple species of cytochrome P-450 more preferentially depending upon the substrate and the concentration of the substrate in microsomal membranes.
利用未经处理、经苯巴比妥处理和经3-甲基胆蒽处理的大鼠的微粒体，研究了添加纯化的NADPH-细胞色素c（P-450）还原酶对微粒体苯胺羟化、对乙氧基苯胺O-脱乙基、乙基吗啡和氨基比林N-脱甲基活性的影响。将纯化的还原酶掺入微粒体中。用还原酶强化微粒体可提高药物氧化活性，但其活性增加的程度因所用底物和微粒体而异。对乙氧基苯胺O-脱乙基活性增强最为显著，其次是苯胺羟化以及氨基比林和乙基吗啡N-脱甲基活性。在经3-甲基胆蒽或苯巴比妥处理的大鼠的微粒体中，这种增强更为明显。当将还原酶掺入微粒体时，α-萘黄酮显著抑制对乙氧基苯胺O-脱乙基活性，这表明在添加还原酶的情况下，大量对该抑制剂敏感的细胞色素P-450能够参与该底物的氧化。较高浓度的苯胺或氨基比林的两个Km值之一会因用纯化的NADPH细胞色素c（P-450）还原酶强化微粒体而改变。根据这些结果，我们提出，NADPH-细胞色素c（P-450）还原酶根据底物和微粒体膜中底物的浓度，更优先地将电子转移到多种细胞色素P-450中选定的一种或两种。
