Molecular characters and recombinant expression of the carboxylesterase gene of the meadow moth Loxostege sticticalis L. (Lepidoptera: Pyralidae)

Insect carboxylesterases are enzymes that catalyze the hydrolysis of ester and amide moieties, which play important roles in insecticide resistance, specifically allelochemical tolerance and developmental regulation. We obtained the cDNA encoding carboxylesterase gene of Loxostege sticticalis (LstiCarE ) by a cDNA library screen. The full cDNA of LstiCarE is 1,980 bp in length, containing an open reading frame (ORF) of 1,875 bp, which encodes a preprotein of 625 amino acid residues. The LstiCarE contains the catalytic triad (Ser-His-Glu), the pentapeptide GxSxG motif and GxxHxxD/E motif, which are typical characteristic of esterases. The GxSxG and GxxHxxD/E motifs of LstiCarE are modified as GCSAG and GxxHxxQ, respectively. The 3-D model structure of LstiCarE showed that Ser197, His440 and Glu321 are aggregated together, which form the catalytic triad. The recombinant LstiCarE were successfully expressed in BL21 cells using recombinant plasmid DNA, and showed high carboxylesterase activity. However, the biochemical and physiological functions of carboxylesterase gene in L. sticticalis requires further investigation.