title: Activation of microsomal epoxide hydrolase by interaction with cytochromes P450: kinetic analysis of the association and substrate-specific activation of epoxide hydrolase function.
abstract: The kinetics of the association between cytochrome P450 (P450) and microsomal epoxide hydrolase (mEH) was studied by means of resonant mirror based on the principle of surface plasmon resonance. The dissociation equilibrium constants (K(D)) for the affinity of P450 enzymes for mEH were estimated by resonant mirror using an optical biosensor cell covalently bound to rat mEH. Comparable K(D) values were obtained for CYP1A1 and 2B1, and these were greater by one order of magnitude than that for the CYP2C11. To clarify the influences of P450 enzymes on the catalytic activity of mEH, the hydrolyzing activity for styrene oxide and benzo(a)pyrene-7,8-oxide [B(a)P-oxide] was analyzed in the presence or absence of P450s. Styrene oxide hydrolysis was activated by all P450s including the CYP1A, 2B, 2C, and 3A subfamilies. In agreement with the association affinity determined by resonant mirror, CYP2C11 tends to have enhanced activity for styrene oxide hydrolysis. On the other hand, B(a)P-oxide hydrolysis was enhanced by only CYP2C11 while CYP1A1 and CYP2B1 had no effect. These results suggest that (1) many P450 enzymes associate nonspecifically with mEH, (2) the CYP2C11 plays a greater role in the association/activation of mEH and (3) the P450-mediated activation of mEH depends upon the substrate of mEH.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higash-ku Fukuoka 812-8582, Japan.
authors.forename: Ken-ichiro
authors.initials: K
authors.lastname: Taura Ki
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Yamada
authors.forename: Eri
authors.initials: E
authors.lastname: Naito
authors.forename: Noritaka
authors.initials: N
authors.lastname: Ariyoshi
authors.forename: Masa-aki
authors.initials: MA
authors.lastname: Mori Ma
authors.forename: Kazuta
authors.initials: K
authors.lastname: Oguri
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001580:Benzopyrenes / Q000737:chemistry; D019363:Cytochrome P-450 CYP1A1 / Q000737:chemistry; D019362:Cytochrome P-450 CYP2B1 / Q000737:chemistry; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry*; D000072467:Cytochrome P450 Family 2; D004851:Epoxide Hydrolases / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry; D007700:Kinetics; D051381:Rats; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000737:chemistry; D013379:Substrate Specificity; D020349:Surface Plasmon Resonance
chemical_list: D001580:Benzopyrenes; D004852:Epoxy Compounds; C023393:benzo(a)pyrene 7,8-oxide; D003577:Cytochrome P-450 Enzyme System; C013690:styrene oxide; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D004851:Epoxide Hydrolases