Kinetic Isotope Effects Implicate Two Electrophilic Oxidants in Cytochrome P450-Catalyzed Hydroxylations
- 26 April 2003
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 125 (20) , 6064-6065
- https://doi.org/10.1021/ja0343858
Abstract
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, CYPΔ2E1, and CYPΔ2E1 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 CYPΔ2E1, 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.Keywords
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