Functional Characterization of Two Carboxylesterase Genes Involved in Pyrethroid Detoxification in <i>Helicoverpa armigera</i>

Abstract

Insect carboxylesterases are major enzymes involved in metabolism of xenobiotics including insecticides. Two carboxylesterase genes, <i>CarE001A</i> and <i>CarE001H</i>, were cloned from the destructive agricultural pest <i>Helicoverpa armigera</i>. Quantitative real-time polymerase chain reaction showed that <i>CarE001A</i> and <i>CarE001H</i> were predominantly expressed in fat body and midgut, respectively; developmental expression analyses found that the expression levels of both CarEs were significantly higher in fifth-instar larvae than in other life stages. Recombinant CarE001A and CarE001H expressed in the <i>Escherichia coli</i> exhibited high enzymatic activity toward α-naphthyl acetate. Inhibition assays showed that organophosphates had strong inhibition on CarEs activity compared to pyrethroids. Metabolism assays indicated that CarE001A and CarE001H were able to metabolize β-cypermethrin and λ<i>-</i>cyhalothrin. Homology modeling and molecular docking analyses demonstrated that β-cypermethrin could fit nicely into the active pocket of both carboxylesterases. These results suggested that <i>CarE001A</i> and <i>CarE001H</i> could play important roles in the detoxification of pyrehtroids in <i>H. armigera</i>.