Degradation of cytochrome P450 2E1: selective loss after labilization of the enzyme.
Degradation of cytochrome P450 2E1: selective loss after labilization of the enzyme.
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DOI：
10.1016/0003-9861(92)90358-4
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发表时间：
1992-02
影响因子：
3.9
通讯作者：
D. J. Tierney;A. Haas;D. Koop
中科院分区：
文献类型：
--
作者：
D. J. Tierney;A. Haas;D. Koop
基于机制的细胞色素 P450 失活可导致血红素、蛋白质或两者的化学修饰，这是由于修饰的血红素与蛋白质共价结合的结果。在本研究中，我们利用 CCl4、1-氨基苯并三唑或 3-氨基-1,2,4-三唑灭活 P450 2E1 的不同模式来研究针对 P450 2E1 从微粒体膜进行蛋白水解的参数。在单次口服丙酮后，在 P450 2E1 最大诱导点用 CCl4 治疗小鼠，导致 P450 2E1 依赖性对硝基苯酚羟基化完全丧失，并且在给药 1 小时内免疫化学可检测蛋白质丧失 75%。在最大诱导点用 1-氨基苯并三唑治疗导致 P450 2E1 依赖性对硝基苯酚羟基化完全丧失，但给药 1 小时后免疫化学可检测蛋白质仅损失 12%。用3-氨基-1,2,4-三唑治疗小鼠导致催化活性和微粒体硝基苯酚羟化酶活性迅速丧失。然而，与CCl4处理不同的是，处理后5和9小时活性和酶水平反弹。在最大诱导点施用P450 2E1配体4-甲基吡唑维持丙酮诱导的P450 2E1催化和免疫化学水平。这些结果表明 P450 2E1 的差异修饰形式表现出对降解的特有敏感性。虽然蛋白质降解有许多潜在途径，但 P450 2E1 的丢失与高分子量微粒体泛素缀合物的形成增加有关。与 P450 2E1 丢失相关的泛素缀合微粒体蛋白的形成表明，泛素化可能代表一种蛋白水解信号，用于快速、选择性地蛋白水解来自内质网的 P450 2E1 的某些不稳定构象。
Mechanism-based inactivation of cytochrome P450 can result in the chemical modification of the heme, the protein, or both as a result of covalent binding of modified heme to the protein. In the present study we took advantage of different modes of inactivation of P450 2E1 by CCl4, 1-aminobenzotriazole, or 3-amino-1,2,4-triazole to investigate parameters which target P450 2E1 for proteolysis from the microsomal membrane. Treatment of mice with CCl4at the point of maximal induction of P450 2E1 after a single oral dose of acetone resulted in the complete loss of P450 2E1-dependentp-nitrophenol hydroxylation and a 75% loss of immunochemically detectable protein within 1 h of administration. Treatment with 1-aminobenzotriazole at the point of maximal induction caused a complete loss of P450 2E1-dependentp-nitrophenol hydroxylation but only a 12% loss of immunochemically detectable protein 1 h after administration. Treatment of mice with 3-amino-1,2,4-triazole caused a rapid loss of both catalytic activity and microsomalp-nitrophenol hydroxylase activity. However, unlike CCl4treatment, the activity and enzyme level rebounded 5 and 9 h after treatment. The P450 2E1 ligand, 4-methylpyrazole, administered at the point of maximal induction maintained the acetone-induced catalytic and immunochemical level of P450 2E1. These results suggest that differentially modified forms of P450 2E1 show a characteristic susceptibility to degradation. While there are many potential pathways for protein degradation, the loss of P450 2E1 was associated with increased formation of hieh molecular weight microsomal ubiquitin conjugates. The formation of ubiquitin-conjugated microsomal protein which correlates with P450 2E1 loss suggests that ubiquitination may represent a proteolytic signal for the rapid and selective proteolysis of certain labilized conformations of P450 2E1 from the endoplasmic reticulum.