L118位点在甜菜夜蛾CYP9A40代谢解毒甲维盐及阿维菌素中的关键作用OA

[Aim]The cytochrome P450 monooxygenase enzyme CYP9A186 of Spodoptera exigua acquired metabolic capability toward emamectin benzoate and abamectin through an F1 16V mutation,mediating high-level resistance to both insecticides.This study targeted the paralogous CYP9A40,which inherently possesses metabolic activity in its wild-type form within the same gene cluster.We introduced an artificial mutation at the homologous site L1 18 of CYP9A40 to explore the functional conservation of this site and the associated risk for resistance evolution.[Methods]The CYP9A40L118V mutant was constructed through artificial point mutation,and expressed in vitro using the insect cell-baculovirus expression system.The decrease in abamectin and emamectin benzoate levels in wild-type CYP9A40,CYP9A40L118Vmutant and CYP9A186F116V mutant after in vitro metabolism was detected using ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS),and the differences in their metabolic activities were compared.Molecular docking simulation was employed to analyze the molecular mechanisms underlying functional changes of mutants.[Results]The wild-type CYP9A40 exhibited metabolic activities toward abamectin and emamectin benzoate[metabolic rate:(5.22±0.02)and(0.90±0.05)pmol/(min·pmol P450),respectively],comparable to those of the CYP9A186F116V mutant[metabolic rate:(4.19±0.04)and(0.88±0.08)pmol/(min·pmol P450),respectively].The L1 18V mutation of CYP9A40 reduced its metabolic rate toward abamectin by 77.8％and completely abolished metabolism activity toward emamectin benzoate.Molecular docking simulation results revealed that the L1 18 V mutation of CYP9A40 disrupted the hydrophobic environment at the bottom of the catalytic pocket,leading to a significant decrease in the polar interactions and binding energy,thereby weakening the substrate binding stability.[Conclusion]CYP9A40 holds significant potential in mediating resistance to abamectins in S.exigua.The L1 18 site of this P450 protein is a critical conserved site for maintaining metabolic function to abamectins,with its side-chain hydrophobicity and spatial conformation being indispensable for substrate binding stability.The functional constraints of this site provide guidance for the development of targeted inhibitors.