Oxidation of 10-undecenoic acid by cytochrome P450BM-3 and its Compound I transient

Abstract

Oxidations of 10-undecenoic acid by cytochrome P450_BM-3 and its Compound I transient were studied. The only product formed in Compound I oxidations was 10,11-epoxyundecanoic acid, whereas the enzyme under turnover conditions gave the epoxide and 9-hydroxy-10-undecenoic acid in a 10 : 90 ratio. Kinetic studies at 0 °C of oxidations by Compounds I formed by MCPBA oxidation and by a photo-oxidation pathway gave the same results, displaying saturation kinetics that yielded equilibrium binding constants and first-order oxidation rate constants that were experimentally indistinguishable. Oxidation of 10-undecenoic acid by Compound I from CYP119 generated by MCBPA oxidation also gave 10,11-epoxyundecanoic acid as the only product. CYP119 Compound I bound the substrate less strongly but reacted with a faster oxidation rate constant than P450_BM-3 Compound I. The kinetic parameters for oxidation of the substrate by P450_BM-3 under turnover conditions were similar to those of the Compound I transient even though the products differed.