Functional important radical-containing intermediates in thiolate-coordinated heme proteins: cytochrome P450 and chloroperoxidase

认为一种化合物I型中间体参与了细胞色素P450的反应周期；然而，它的电子结构直到现在才被确定。此外，在分流途径中，使用过氧酸作为氧化剂，并没有证明确实存在Fe(IV)=0卟啉p-阳离子自由基体系。因此，我们建议利用EPR和Mössbauer光谱来研究P450反应中铁的价态和自旋态、自由基的形成以及铁与自由基之间可能的相互作用。为此，P450将通过血红素替代法制备富含57fe的卟啉；使用过氧酸的反应中间体，在底物存在或不存在的情况下，将被冷冻淬火技术捕获。对P450的研究将通过对富含57fe的氯过氧化物酶作为血红素硫酸盐蛋白家族的另一成员的比较研究来补充。

It is believed that a compound I type intermediate is involved in the reaction cycle of cytochrome P450; however, its eletronic structure has not been determined until now. Also, it has not been shown that in the shunt pathway, using peroxy acids as oxidizing agents, a Fe(IV)=0 porphyrin p-cation radical system does really exist. We therefore propose to investigate the valence and spin state of iron, the formation of radicals and the possible interaction between iron and radical in P450 reactions by EPR and Mössbauer spectroscopy. For this purpose P450 will be prepared with 57Fe-enriched porphyrin by heme replacement; reaction intermediates using peroxy acids, in the presence and in the absence of substrate, will be trapped by the freeze-quench technique. The studies on P450 will be complemented by a comparative study on 57Fe-enriched chloroperoxidase as another member of the heme-thiolate protein family.