Cytochrome b5 Is Essential for Cytochrome P450 6D1-Mediated Cypermethrin Resistance in LPR House Flies
Cytochrome P450 monooxygenase-mediated detoxification is a very important mechanism of resistance to insecticides. In the LPR strain of house fly, the major mechanism of resistance to pyrethroids is monooxygenase-mediated metabolism due to the overexpression of cytochrome P450 6D1 (CYP6D1). Although the role of CYP6D1 in pyrethroid resistance has been demonstrated, there is no information as to whether cytochrome b5 is involved in this reaction and what the major CYP6D1-specific metabolite is. Using a cytochrome b5 antiserum we demonstrate that cytochrome b5 is required for the elevated level of CYP6D1-mediated cypermethrin metabolism observed in microsomes from the resistant LPR strain compared to a susceptible strain. Therefore, cytochrome b5 is directly involved in this monooxygenase-mediated resistance. NADH has no significant effect on this metabolism, suggesting that in vitro the second electron source for CYP6D1 is NADPH when cypermethrin is the substrate. Using GC-MS, the primary CYP6D1 specific metabolite formed in vitro was identified as 4'-OH cypermethrin.
Zhang
M
Department of Entomology, Cornell University, Ithaca, New York, 14853-0999
Scott
JG