Characterization of the enzymatic and nonenzymatic peroxidative degradation of iron porphyrins and cytochrome P-450 heme.
Characterization of the enzymatic and nonenzymatic peroxidative degradation of iron porphyrins and cytochrome P-450 heme.
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DOI：
10.1021/bi00334a027
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发表时间：
1985-06
期刊：
影响因子：
2.9
通讯作者：
Schaefer Wh;Thomas M. Harris;Guengerich Fp
中科院分区：
文献类型：
--
作者：
Schaefer Wh;Thomas M. Harris;Guengerich Fp
在NADPH和O2存在下，纯化的细胞色素P-450 （P-450）和游离的铁原卟啉IX都被NADPH-P-450还原酶破坏。这一过程似乎是由O2还原产生的H2O2介导的。从H2O2与原卟啉铁-血液酸、甲基乙烯基马来酰亚胺和4种二吡啶前驱剂的反应中鉴定出6种主要产物。用质谱法和核磁共振氢谱法对前驱剂的结构进行了鉴定。游离卟啉铁IX和P-450以相似的相对比例产生相同的产物。大鼠肝微粒体中的P-450血红素在O2、NADPH和NaN3（过氧化氢酶抑制剂）或Fe-ADP（促进脂质过氧化）存在下降解；产物主要是血亚酸、甲基乙烯基马来酰亚胺和少量的一种前驱剂。过氧化异丙苯和碘基苯对微粒体P-450血红素的破坏仅检测到这两种马来酰亚胺。根据H2O2与几种金属-辛乙基乙基卟啉配合物和游离辛乙基卟啉的反应，铁原卟啉IX中螯合的铁是H2O2降解所必需的。胆绿素不是血红素形成马来酰亚胺和前驱体的中间体。用由铁八乙基卟啉制备的四乙基前驱物进行的实验表明，前驱物不会进一步裂解形成马来酰亚胺。氧化血红素破坏的机制与这些观察一致提出。
Both purified cytochrome P-450 (P-450) and free ferriprotoporphyrin IX are destroyed by NADPH-P-450 reductase in the presence of NADPH and O2. The process appears to be mediated by H2O2 generated by reduction of O2. Six major products were identified from the reaction of H2O2 with ferri-protoporphyrin IX-hematinic acid, methylvinylmaleimide, and four dipyrrolic propentdyopents. The structures of the propentdyopents were elucidated by mass spectrometry and 1H NMR methods. Both free ferriprotoporphyrin IX and P-450 yielded these same products in similar relative ratios. P-450 heme in rat liver microsomes was degraded in the presence of O2 and NADPH and either NaN3 (a catalase inhibitor) or Fe-ADP (which promotes lipid peroxidation); the products were primarily hematinic acid, methylvinylmaleimide, and small quantities of one propentdyopent. Only the two maleimides were detected in the destruction of microsomal P-450 heme by cumene hydroperoxide and iodosylbenzene. On the basis of the reaction of H2O2 with several metal-octaethylethylporphyrin complexes and free octaethylporphyrin, the iron chelated in ferriprotoporphyrin IX is required for degradation by H2O2. Biliverdin is not an intermediate in the formation of maleimides and propentdyopents from heme. Experiments using the tetraethylpropentdyopent produced from ferrioctaethylporphyrin suggest that propentdyopents are not further cleaved to form the maleimides. A mechanism for oxidative heme destruction consistent with these observations is proposed.