CHARACTERIZATION OFMOSQUITO CYP6P7 ANDCYP6AA3: DIFFERENCES INSUBSTRATE PREFERENCE ANDKINETIC PROPERTIES

摘要

Cytochrome P450 monooxygenases are involved in insecticide resistancein insects. We previously observed an increase in CYP6P7 andCYP6AA3 mRNA expression in Anopheles minimus mosquitoes duringthe selection for deltamethrin resistance in the laboratory. CYP6AA3 hasbeen shown to metabolize deltamethrin, while no information is knownfor CYP6P7. In this study, CYP6P7 was heterologously expressed in theSpodoptera frugiperda (Sf9) insect cells via baculovirus-mediated expression system. The expressed CYP6P7 protein was used for exploitation of its enzymatic activity against insecticides after recon- stitution with the An. minimus NADPH-cytochrome P450 reductase enzyme in vitro. The ability of CYP6P7 to metabolize pyrethroids andinsecticides in the organophosphate and carbamate groups was comparedwith CYP6AA3. The results revealed that both CYP6P7 and CYP6AA3proteins could metabolize permethrin, cypermethrin, and deltamethrinpyrethroid insecticides, but showed the absence of activity againstbioallethrin (pyrethroid), chlorpyrifos (organophosphate), and propoxur(carbamate). CYP6P7 had limited capacity in metabolizing lambda-cyhalothrin(pyrethroid), while CYP6AA3 displayed activity toward lambda-cyhalothrin.Kinetic properties suggested that CYP6AA3 had higher efficiency inmetabolizing type I than type II pyrethroids, while catalytic efficiency ofCYP6P7 toward both types was not significantly different. Their kineticparameters in insecticide metabolism and preliminary inhibition studiesby test compounds in the flavonoid, furanocoumarin, and methylenedioxyphenyl groups elucidated that CYP6P7 had different enzyme properties compared with CYP6AA3.