FORMATION OF CYTOCHROME-P-450 CONTAINING HEME OR COBALT-PROTOPORPHYRIN IN LIVER HOMOGENATES OF RATS TREATED WITH PHENOBARBITAL AND ALLYLISOPROPYLACETAMIDE
FORMATION OF CYTOCHROME-P-450 CONTAINING HEME OR COBALT-PROTOPORPHYRIN IN LIVER HOMOGENATES OF RATS TREATED WITH PHENOBARBITAL AND ALLYLISOPROPYLACETAMIDE
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DOI：
10.1042/bj2220453
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发表时间：
1984-01-01
影响因子：
4.1
通讯作者：
SMITH, EL
中科院分区：
文献类型：
--
作者：
BONKOVSKY, HL;SINCLAIR, JF;SMITH, EL
有效的卟素烯丙基异丙基乙酰胺和相关化合物可降低肝脏细胞色素P-450的浓度。这种减少尤其发生在苯巴比妥诱导的细胞色素P-450中，并且是由细胞色素P-450的血红素的自杀性分解引起的。定量火箭免疫电泳法显示，苯巴比妥诱导的主要肝细胞色素P-450的蛋白部分在处理后1h未见减少，但在处理20h后显著减少(为苯巴比妥对照组的43%)。与之相反，用分光光度法测得细胞色素P-450的总浓度在1小时和20小时均下降到对照组的30-40%。细胞色素P-450依赖的乙基吗啡和苯丙胺的脱甲基化也有类似程度的减少。将大鼠处死前1h用烯丙基异丙基乙酰胺处理的大鼠肝匀浆与血红素孵育，脱脂蛋白可重组出功能完整的细胞色素P-450。在用苯巴比妥单独处理的大鼠中，与血红素孵育可使可测细胞色素P-450活性增加到69%，乙基吗啡脱甲基酶增加到%，苯丙胺脱甲基酶增加到93%。然而，在烯丙基异丙基乙酰胺处理20h后，细胞色素P-450在与血红素孵育后很少或没有恢复。当肝匀浆与钴和原卟啉孵育后，微粒体蛋白经聚丙烯酰胺凝胶电泳，发现钴原卟啉与相对分子质量为50,000-53,000的蛋白质特异地结合。当比较给予烯丙基异丙基乙酰胺1h和20h的大鼠肝匀浆时，凋亡素P-450含量较多的大鼠肝脏中这种联系的程度更高，这表明钴原卟啉与凋亡素有关。这些数据为深入了解血红素与细胞色素P-450的蛋白质部分以及影响该蛋白质分解的因素提供了洞察力。
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 heme 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 heme, functional holocytochrome P-450 could be reconstituted from the apoprotein. Incubation with heme 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 heme. When liver homogenates were incubated with Co and protoporphyrin, and microsomal proteins were then subjected to polyacrylamide-gel electrophoresis, cobalt-protoporphyrin was found specifically associated with proteins of MW 50,000-53,000. When homogenates from rats given allylisopropylacetamide for 1 h or 20 h were compared, 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 heme with the protein moiety of cytochrome P-450 and factors affecting breakdown of this protein.