Kinetic isotope effects implicate two electrophilic oxidants in cytochrome p450-catalyzed hydroxylations.
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.
Newcomb
Martin
M
Department of Chemistry, University of Illinois at Chicago, 60607, USA. men@uic.edu
Aebisher
David
D
Shen
Runnan
R
Chandrasena
R Esala P
RE
Hollenberg
Paul F
PF
Coon
Minor J
MJ
D000438:Alcohols / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000378:metabolism*; D003903:Deuterium; D006900:Hydroxylation; D007700:Kinetics; D016877:Oxidants / Q000737:chemistry / Q000378:metabolism
D000438:Alcohols; D016877:Oxidants; D003577:Cytochrome P-450 Enzyme System; D003903:Deuterium