Li-Sha Bai, Jing-Jing Xu, Cai-Xia Zhao, Ya-Li Chang, Yan-Ling Dong, Kai-Ge Zhang, Yong-Qiang Li, Yi-Ping Li, Zhi-Qing Ma, Xi-Li Liu. Enhanced hydrolysis of β-cypermethrin caused by deletions in the Glycin-Rich Region of carboxylesterase 001G from Helicoverpa armigera

Enhanced hydrolysis of β-cypermethrin caused by deletions in the Glycin-Rich Region of carboxylesterase 001G from Helicoverpa armigera

Li-Sha Bai, Jing-Jing Xu, Cai-Xia Zhao, Ya-Li Chang, Yan-Ling Dong, Kai-Ge Zhang, Yong-Qiang Li, Yi-Ping Li, Zhi-Qing Ma, Xi-Li Liu

Pest Management Science

DOI:10.1002/ps.6242

Abstract

Background: Carboxylesterase is a major class of enzymes involved in the detoxification of toxic xenobiotics in various insect species. Previous work has shown that the carboxylesterase gene CarE001G found in Helicoverpa armigera is more active and can metabolize synthesized pyrethroids, such as β-cypermethrin, one of the commonly used commercial insecticides for lepidopteran pest control. In addition, CarE001G is very special as it has a very specific Glycine-Rich Region located adjacent to its C-terminal. But whether mutations in this unique sequence can change the biochemistry and function of CarE001G are unknown.

Results: In this study, four CarE001G's variants with different deletions in the Glycine-Rich Region were obtained and functionally expressed in the Escherichia coli. The recombinant proteins were purified and confirmed by Western blot and mass spectrometry analyses. These mutant enzymes showed high catalytic efficiency toward the model substrate α-naphthyl acetate. Inhibition study showed that β-cypermethrin had relatively strong inhibition on CarE activities. In vitro metabolism assay showed that the mutant enzymes significantly enhanced their metabolic activities toward β-cypermethrin with specific activities between 4.0-5.6 nM·min-1 ·mg-1 protein. Molecular docking analyses consistently demonstrated that deletion mutations in the Glycine-Rich Region may facilitate the anchoring of the β-cypermethrin molecule in the active binding pocket of the mutant enzymes.

Conclusion: These data show that deletion mutations can cause qualitative change in the capacity of CarEs in the detoxification of β-cypermethrin. This indicates that deletion mutations in the Glycine-Rich Region may have the potential to cause SP resistance in H. armigera in the future.