Bonkovsky H L, Sinclair J F, Healey J F, Sinclair P R, Smith E L
Biochem J. 1984 Sep 1;222(2):453-62. doi: 10.1042/bj2220453.
The potent porphyrogen allylisopropylacetamide and related compounds decrease hepatic concentrations of cytochrome P-450. This decrease occurs particularly in phenobarbital-induced cytochrome P-450 and is caused by suicidal breakdown of the haem of cytochrome P-450. Quantitative rocket immunoelectrophoresis showed that the protein moiety of the major phenobarbital-inducible form of hepatic cytochrome P-450 was not diminished up to 1 h, but was markedly decreased (to 43% of that of the phenobarbital-treated control) at 20 h after allylisopropylacetamide treatment. In contrast, the concentration of total cytochrome P-450, measured spectrophotometrically, decreased to 30-40% of the control at both 1 and 20 h after allylisopropylacetamide. Cytochrome P-450-dependent demethylations of ethylmorphine and benzphetamine decreased to a similar extent. When liver homogenates from rats treated with allylisopropylacetamide 1 h before being killed were incubated with haem, functional holocytochrome P-450 could be reconstituted from the apoprotein. Incubation with haem increased spectrophotometrically measurable cytochrome P-450 to 69%, ethylmorphine demethylase to 64% and benzphetamine demethylase to 93% of the activities in rats treated with phenobarbital alone. At 20 h after allylisopropylacetamide treatment, however, little or no reconstitution of cytochrome P-450 occurred after incubation with haem. When liver homogenates were incubated with cobalt and protoporphyrin, and microsomal proteins were then subjected to polyacrylamide-gel electrophoresis, cobalt-protoporphyrin was found specifically associated with proteins of Mr 50 000-53 000. When homogenates from rats given allylisopropylacetamide for 1 h or 20 h were compared, it was found that the extent of this association was higher in livers from the rats containing more apocytochrome P-450, suggesting that cobalt-protoporphyrin had associated with the apocytochrome. The data provide insight into the association of haem with the protein moiety of cytochrome P-450 and factors affecting breakdown of this protein.
强效的致卟啉剂烯丙基异丙基乙酰胺及相关化合物可降低细胞色素P - 450的肝脏浓度。这种降低尤其发生在苯巴比妥诱导的细胞色素P - 450中，是由细胞色素P - 450血红素的自杀性分解所致。定量火箭免疫电泳显示，肝脏细胞色素P - 450主要的苯巴比妥诱导型的蛋白质部分在1小时内没有减少，但在烯丙基异丙基乙酰胺处理后20小时显著减少（降至苯巴比妥处理对照组的43%）。相比之下，用分光光度法测定的总细胞色素P - 450浓度在烯丙基异丙基乙酰胺处理后的1小时和20小时均降至对照组的30 - 40%。细胞色素P - 450依赖的乙基吗啡和苄非他明的去甲基化程度也有类似程度的降低。当处死前1小时用烯丙基异丙基乙酰胺处理的大鼠肝脏匀浆与血红素一起孵育时，功能性全细胞色素P - 450可由脱辅基蛋白重构。与血红素孵育后，分光光度法可测定的细胞色素P - 450增加到单独用苯巴比妥处理的大鼠活性的69%，乙基吗啡脱甲基酶增加到64%，苄非他明脱甲基酶增加到93%。然而，在烯丙基异丙基乙酰胺处理后20小时，与血红素孵育后细胞色素P - 450几乎没有或没有重构。当肝脏匀浆与钴和原卟啉一起孵育，然后对微粒体蛋白进行聚丙烯酰胺凝胶电泳时，发现钴 - 原卟啉与分子量为50000 - 53000的蛋白质特异性相关。当比较给予烯丙基异丙基乙酰胺1小时或20小时的大鼠的匀浆时，发现这种结合程度在含有更多脱辅基细胞色素P - 450的大鼠肝脏中更高，这表明钴 - 原卟啉已与脱辅基细胞色素结合。这些数据为血红素与细胞色素P - 450蛋白质部分的结合以及影响该蛋白质分解的因素提供了见解。
