Zurek Jolanta, Foloppe Nicolas, Harvey Jeremy N, Mulholland Adrian J
Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol, UK BS8 1TS.
Org Biomol Chem. 2006 Nov 7;4(21):3931-7. doi: 10.1039/b611653a. Epub 2006 Oct 3.
The fundamental nature of reactivity in cytochrome P450 enzymes is currently controversial. Modelling of bacterial P450cam has suggested an important role for the haem propionates in the catalysis, though this finding has been questioned. Understanding the mechanisms of this enzyme family is important both in terms of basic biochemistry and potentially in the prediction of drug metabolism. We have modelled the hydroxylation of camphor by P450cam, using combined quantum mechanics/molecular mechanics (QM/MM) methods. A set of reaction pathways in the enzyme was determined. We were able to pinpoint the source of the discrepancies in the previous results. We show that when a correct ionization state is assigned to Asp297, no spin density appears on the haem propionates and the protein structure in this region remains preserved. These results indicate that the haem propionates are not involved in catalysis.
细胞色素P450酶反应活性的基本性质目前存在争议。对细菌P450cam的建模表明血红素丙酸酯在催化过程中起重要作用，不过这一发现受到了质疑。从基础生物化学角度以及在预测药物代谢方面理解这个酶家族的机制都很重要。我们使用量子力学/分子力学（QM/MM）相结合的方法对P450cam催化樟脑羟基化反应进行了建模。确定了该酶中的一组反应途径。我们能够找出先前结果中差异的根源。我们表明，当给Asp297指定正确的电离状态时，血红素丙酸酯上不会出现自旋密度，并且该区域的蛋白质结构得以保留。这些结果表明血红素丙酸酯不参与催化作用。
