OLEFIN OXIDATION BY CYTOCHROME-P-450 - EVIDENCE FOR GROUP MIGRATION IN CATALYTIC INTERMEDIATES FORMED WITH VINYLIDENE-CHLORIDE AND TRANS-1-PHENYL-1-BUTENE
OLEFIN OXIDATION BY CYTOCHROME-P-450 - EVIDENCE FOR GROUP MIGRATION IN CATALYTIC INTERMEDIATES FORMED WITH VINYLIDENE-CHLORIDE AND TRANS-1-PHENYL-1-BUTENE
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DOI：
10.1021/bi00293a005
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发表时间：
1983-01-01
期刊：
影响因子：
2.9
通讯作者：
GUENGERICH, FP
中科院分区：
文献类型：
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作者：
LIEBLER, DC;GUENGERICH, FP
摘要：大鼠肝细胞色素P-450 （P-450）在微粒体和纯化酶系统中氧化致癌物氯乙烯（VDC）产生C1CH2C02H和Cl2CHCHO，并伴随8种P-450同工酶中的3种自杀性失活。通过化学和动力学研究评价了VDC氧化物在C1CH2C02H和Cl2CHCHO生产中的中间作用。以w-氯过氧苯甲酸氧化VDC制备的真实VDC氧化物，经核磁共振（NMR）和质谱分析表征，水溶液分解不能生成Cl2CHCHO，仅在pH< 2时生成C1CH2C02H。此外，在碘苯支持下，P-450氧化VDC生成VDC氧化物的动力学研究不支持其在C1CH2C02H和Cl2CHCHO形成中的专门中间体作用。[2,2 - 2h2] VDC通过添加醛脱氢酶和NAD+的微粒体被氧化为C12C2HC02H，表明在前体Cl2C2HC2HO的形成过程中氘的转移。为了验证P-450的血红素Fe （III）作为路易斯酸催化瞬态环氧化物中间体重排到Cl2CHCHO的假设，研究了Fe （III）存在下VDC氧化物的分解。饱和二氧化二氮的CHC13使环氧化物向Cl2CHCHO的后排约为50%，但CHC13中同等浓度的（mes’o-四苯基卟啉）氯化铁（III）和高纯度的细胞色素P-450均不能从VDC氧化物中产生Cl2CHCHO。使用反式-1-苯基丁烯1,2 -氧化物（一种稳定的模型环氧化物）进行的平行研究表明，尽管环氧化物与P-450确实发生了结合，但铁P-450并没有催化环氧化物的降解。母体烯烃，反式-1-苯基-1-的氧化
Daniel C. Liebler and F. Peter Guengerich* abstract: Oxidation of the carcinogen vinylidene chloride (VDC) by rat liver cytochrome P-450 (P-450) in microsomal and purified enzyme systems produced both C1CH2C02H and Cl2CHCHO with concomitant suicide inactivation of three of the eight P-450 isozymes examined. The proposed interme-diary role of VDC oxide in C1CH2C02H and Cl2CHCHO production was evaluated by using chemical and kinetic studies. Aqueous decomposition of authentic VDC oxide, prepared by w-chloroperoxybenzoic acid oxidation of VDC and characterized by nuclear magnetic resonance (NMR) and mass spectrometry, failed to produce Cl2CHCHO and yielded C1CH2C02H only at pH< 2. Moreover, kinetic studies of VDC oxide production in the iodosobenzene-supported oxidation of VDC by P-450 did not support its proposed role as an obligate intermediate in the formation of C1CH2C02H and Cl2CHCHO.[2, 2-2H2] VDC was synthesized and found to be oxidized to C12C2HC02H by microsomes supplemented with aldehyde dehydrogenase and NAD+, indicatingtransfer of deuterium in the formation of the precursor Cl2C2HC2HO. To test the hypothesis that the heme Fe (III) of P-450 acts as a Lewis acid in catalyzing the rearrangement of a transient epoxide intermediate to Cl2CHCHO, the decomposition of VDC oxide in the presence of Fe (III) was studied. WhileFeBr3-saturated CHC13 effected approximately 50% rear-rangement of epoxide to Cl2CHCHO, neither an equivalent concentration of (mes'o-tetraphenylporphyrinato) iron (III) chloride in CHC13 nor highly purified cytochrome P-450 in aqueous buffer produced Cl2CHCHO from VDC oxide. Parallel studies using trans-1-phenylbutene 1, 2-oxide, a stable model epoxide, indicated that, although binding of epoxide to P-450 did occur, ferric P-450 did not catalyze epoxide deg-radation. Oxidation of the parent olefin, trans-1-phenyl-1-