Newcomb Martin, Aebisher David, Shen Runnan, Chandrasena R Esala P, Hollenberg Paul F, Coon Minor J
Department of Chemistry, University of Illinois at Chicago, 60607, USA.
J Am Chem Soc. 2003 May 21;125(20):6064-5. doi: 10.1021/ja0343858.
Intramolecular kinetic isotope effects (KIEs) were determined for cytochrome P450-catalyzed hydroxylation reactions of methyl-dideuterated trans-2-phenylcyclopropylmethane-d2 (1-d2), which gives two products from oxidation of the methyl group, trans-2-phenylcyclopropylmethanol (2) and 1-phenyl-3-buten-1ol (3). In oxidations of each enantiomer of 1-d2 with three P450 enzymes (CYP2B1, CYPDelta2E1, and CYPDelta2E1 T303A), the apparent intramolecular KIEs were different for products 2 and 3 in all cases and different for each enzyme-substrate combination. In oxidations of each enantiomer of undeuterated 1-d0 and trideuteriomethyl 1-d3 by CYP2B1 and CYPDelta2E1, the ratio of products 2/3 decreased for 1-d3 in comparison to 1-d0 in all cases. The results require multiple pathways for P450-catalyzed hydroxylation and are consistent with the "two-oxidants" model, where hydroxylation is effected by both the hydroperoxy-iron species and the iron-oxo species. The results are not consistent with predictions of the "two-states" model for P450-catalyzed hydroxylations, where oxidations occur from a low-spin state and a high-spin state of iron-oxo.
测定了细胞色素P450催化的甲基 - 二氘代反式 - 2 - 苯基环丙基甲烷 - d2(1 - d2)的羟基化反应的分子内动力学同位素效应(KIEs),该反应甲基氧化产生两种产物,即反式 - 2 - 苯基环丙基甲醇(2)和1 - 苯基 - 3 - 丁烯 - 1 - 醇(3)。在用三种P450酶(CYP2B1、CYPDelta2E1和CYPDelta2E1 T303A)氧化1 - d2的各对映体时,在所有情况下产物2和3的表观分子内KIEs均不同,且每种酶 - 底物组合的KIEs也不同。在用CYP2B1和CYPDelta2E1氧化未氘代的1 - d0和三氘代甲基1 - d3的各对映体时,在所有情况下,与1 - d0相比,1 - d3的产物2/3比率降低。结果表明细胞色素P450催化的羟基化反应存在多种途径,这与“双氧化剂”模型一致,即羟基化由氢过氧铁物种和铁氧物种共同作用。结果与细胞色素P450催化羟基化反应的“双态”模型预测不一致,该模型认为氧化发生在铁氧的低自旋态和高自旋态。