Abstract:

【Objective】 The objective of the study is to clone carboxylesterase gene and provide a molecular basis for insecticide resistance of organophosphates (OPs). 【Method】 A full-length cDNA clone was identified to code for a carboxylesterase by immuno-screening of the Helicoverpa armigera midgut cDNA expression library and expressed into Escherichia coli. The carboxylesterase activity of HC3 was characterized with the α-NA as a substrate and its enzyme activity of HC3 was analyzed. 【Result】 The hc3 is 2 896 bp in length, which encodes 795 amino acids (GenBank accession number is GU119888). The predicted isoelectric point of HC3 is 3.94. The HC3 possesses a catalytic triad, consisting of a Ser, a His and a Glu residue (Ser204, Glu331 and His444). The activity for HC3 is 0.32 mmol/100 μL enzyme buffer. 【Conclusion】 A cDNA encoding carboxylesterase was cloned and expressed from Helicoverpa armigera. A noval GDE hydrophilic region was found in HC3. All the above understanding will further explore the three-dimensional structure, hydrolysis of carboxylesterase and provide possibility for the design of new types of pesticides.

Key words: Helicoverpa armigera (Hübner), cDNA expression library, carboxylesterase, activity analysis