Imperatorin is a mechanism-based inactivator of CYP2B6.
Imperatorin (IMP) is the major active ingredient in many common medicinal herbs. We examined the irreversible inhibitory effect of IMP on CYP2B6. IMP produced a time- and concentration-dependent inactivation of CYP2B6. About 70% of activity of CYP2B6 was suppressed after its incubation with 1.5 μM IMP for 9 minutes. KI and kinact were found to be 0.498 μM and 0.079 min(-1), respectively. The loss of CYP2B6 activity required the presence of NADPH. Glutathione and catalase/superoxide dismutase showed little protection against the IMP-induced enzyme inactivation. Ticlopidine, a substrate of CYP2B6, showed protection of the enzyme against the inactivation induced by IMP. The estimated partition ratio of the inactivation was approximately 4. Additionally, a γ-ketoenal intermediate was identified in microsomal incubations with IMP. CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP2E1, CYP3A4, and CYP3A5 were found to be involved in bioactivation of IMP. In conclusion, IMP is a mechanism-based inactivator of CYP2B6. The formation of γ-ketoenal intermediate may account for the enzyme inactivation.
School of Pharmacy (L.Z., J.C., D.L., L.J., Y.P.), Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education (J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, P. R. China; and Center for Developmental Therapeutics, Seattle Children's Research Institute, Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington (J.Z.).
Liwei
L
Zheng
School of Pharmacy (L.Z., J.C., D.L., L.J., Y.P.), Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education (J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, P. R. China; and Center for Developmental Therapeutics, Seattle Children's Research Institute, Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington (J.Z.).
Jiaojiao
J
Cao
School of Pharmacy (L.Z., J.C., D.L., L.J., Y.P.), Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education (J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, P. R. China; and Center for Developmental Therapeutics, Seattle Children's Research Institute, Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington (J.Z.).
Dan
D
Lu
School of Pharmacy (L.Z., J.C., D.L., L.J., Y.P.), Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education (J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, P. R. China; and Center for Developmental Therapeutics, Seattle Children's Research Institute, Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington (J.Z.).
Lin
L
Ji
School of Pharmacy (L.Z., J.C., D.L., L.J., Y.P.), Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education (J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, P. R. China; and Center for Developmental Therapeutics, Seattle Children's Research Institute, Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington (J.Z.) jiang.zheng@seattlechildrens.org yingpeng1999@163.com.
Ying
Y
Peng
School of Pharmacy (L.Z., J.C., D.L., L.J., Y.P.), Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education (J.Z.), Shenyang Pharmaceutical University, Shenyang, Liaoning, P. R. China; and Center for Developmental Therapeutics, Seattle Children's Research Institute, Division of Gastroenterology and Hepatology, Department of Pediatrics, University of Washington School of Medicine, Seattle, Washington (J.Z.) jiang.zheng@seattlechildrens.org yingpeng1999@163.com.
Jiang
J
Zheng
D000818:Animals; D002374:Catalase / Q000378:metabolism; D065702:Cytochrome P-450 CYP2B6 / Q000378:metabolism*; D011564:Furocoumarins / Q000378:metabolism* / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000378:metabolism; D013988:Ticlopidine / Q000494:pharmacology
D011564:Furocoumarins; D009249:NADP; D002374:Catalase; D065702:Cytochrome P-450 CYP2B6; D013482:Superoxide Dismutase; D005978:Glutathione; C031534:imperatorin; D013988:Ticlopidine