Mechanism-based inactivation of cytochrome P450 2B6 by isopsoralen.
1. Isopsoralen (IPRN) is a major component in many traditional medicinal herbs widely used in Asian countries. The objective of the present study was to investigate the inhibitory effect of IPRN on cytochrome P450 2B6 (CYP2B6) and the mechanism involved in the enzyme inactivation. 2. Pre-incubation of CYP2B6 with IPRN resulted in a time- and concentration-dependent enzyme activity loss. The values of K(I) and k(inact) were found to be 7.89 μM and 0.067 min(-1), respectively. Ticlopidine exhibited protective effect on the IPRN-induced enzyme inactivation. The estimated partition ratio of the inactivation was 122. The GSH trapping experiments indicate that an epoxide and/or γ-ketoenal intermediate were/was generated in IPRN-fortified microsomal incubations. The synthetic work verified the formation of the reactive intermediate(s). Additionally, CYPs2E1, 2C19, 2B6 and 1A2 were found to be the major enzymes participating in the bioactivation of IPRN. 3. IPRN was characterized as a mechanism-based inactivator of CYP2B6. An IPRN-derived furanoepoxide and/or γ-ketoenal intermediate(s) were/was generated and may be responsible for the inactivation of CYP2B6.
a School of Pharmacy and.
Dan
D
Lu
a School of Pharmacy and.
Lin
L
Ji
a School of Pharmacy and.
Liwei
L
Zheng
a School of Pharmacy and.
Jiaojiao
J
Cao
a School of Pharmacy and.
Ying
Y
Peng
b Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education , Shenyang , Liaoning , P. R. China and.|c Division of Gastroenterology and Hepatology, Department of Pediatrics , Center for Developmental Therapeutics, Seattle Children's Research Institute, University of Washington School of Medicine , Seattle , WA , USA.
Jiang
J
Zheng
D000818:Animals; D002374:Catalase / Q000378:metabolism; D065702:Cytochrome P-450 CYP2B6 / Q000378:metabolism*; D065607:Cytochrome P-450 Enzyme Inhibitors / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D011564:Furocoumarins / Q000737:chemistry / Q000494:pharmacology*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D013058:Mass Spectrometry; D055442:Metabolome / Q000187:drug effects; D009249:NADP / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity / Q000187:drug effects; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors
D065607:Cytochrome P-450 Enzyme Inhibitors; D011564:Furocoumarins; D009249:NADP; C011659:angelicin; D002374:Catalase; D065702:Cytochrome P-450 CYP2B6; D013482:Superoxide Dismutase; D005978:Glutathione
Cytochrome P450 2B6; Isopsoralen; mechanism-based inactivator; reactive metabolite