title: Differential cumene hydroperoxide sensitivity of cytochrome P-450 enzymes IA1 and IIB1 determined by their way of membrane incorporation.
abstract: The cytochrome P-450-dependent O-dealkylation of alkoxyresorufins was used to study the effect of cumene hydroperoxide on cytochrome P-450 IIB1 and IA1 in microsomal and reconstituted systems. In liver microsomal systems from respectively phenobarbital and 3-methylcholanthrene pretreated male Wistar rats, cytochrome P-450 IIB1-dependent pentoxyresorufin-O-dealkylation appeared to be more sensitive to cumene hydroperoxide treatment than cytochrome P-450 IA1-dependent ethoxyresorufin-O-dealkylation. This phenomenon was also observed when the cumene hydroperoxide sensitivity of P-450 IIB1 and IA1 was studied in an isosafrole pretreated rat liver microsomal system. The decrease in alkoxy-O-dealkylating activities appeared to proceed by destruction of the cytochrome P-450 component of the enzyme system. Purification and reconstitution of the enzyme system components in a system in which the isolated proteins were not incorporated into a membrane resulted in the disappearance of the difference in sensitivity between the two P-450 enzymes. However, in a reconstituted system with membrane incorporated proteins, again cytochrome P-450 IIB1 expressed a higher sensitivity towards cumene hydroperoxide than cytochrome P-450 IA1. From this it was concluded that the differential cumene hydroperoxide sensitivity of cytochrome P-450 IIB1 and IA1 is not caused by an intrinsic difference in their sensitivity but by a differential effect of membrane incorporation on their cumene hydroperoxide sensitivity.
authors.affiliation: Department of Biochemistry, Agricultural University, Wageningen, Netherlands.
authors.forename: W G
authors.initials: WG
authors.lastname: Balvers
authors.forename: M G
authors.initials: MG
authors.lastname: Boersma
authors.forename: C
authors.initials: C
authors.lastname: Veeger
authors.forename: I M
authors.initials: IM
authors.lastname: Rietjens
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001555:Benzene Derivatives / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D065607:Cytochrome P-450 Enzyme Inhibitors; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D015227:Lipid Peroxidation; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012451:Safrole / Q000494:pharmacology; D013250:Steroid Hydroxylases / Q000037:antagonists & inhibitors*
chemical_list: D001555:Benzene Derivatives; D065607:Cytochrome P-450 Enzyme Inhibitors; D008748:Methylcholanthrene; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C025619:steroid 16-beta-hydroxylase; C007164:cumene hydroperoxide; D012451:Safrole; C015959:isosafrole; D010634:Phenobarbital