Small peptides inhibit gut trypsin-like proteases and impair Anticarsia gemmatalis (Lepidoptera: Noctuidae) survival and development.

Background: Anticarsia gemmatalis larvae are key defoliating pests of soybean plants. Inorganic insecticides, harmful to the environment and human health, are the main molecules used in the control of this pest. To apply more sustainable management methods, organic molecules with high specificities, such as proteinaceous protease inhibitors, have been sought. Thus, molecular docking studies, kinetics assays, and biological tests were performed to evaluate the inhibitory activity of two peptides (GORE1 and GORE2) rationally designed to inhibit trypsin-like enzymes, which are the main proteases of A. gemmatalis midgut.

Results: The molecular docking simulations revealed critical hydrogen bonding patterns of the peptides with key active site residues of trypsin-like proteases of A. gemmatalis and other Lepidopteran insects. The negative values of binding energy indicate that hydrogen bonds potentiate the tight binding of the peptides with trypsin-like proteases, predicting an effective inhibition. The inhibition's rate constants (Ki) were 0.49 and 0.10 mM for GORE1 and GORE2, resulting in effective inhibition of the activity trypsin on the L-BApNA substrate in the in vitro tests, indicating that the peptide GORE2 has higher inhibitory capacity on the A. gemmatalis trypsins. In addition, the two peptides were determined to be reversible competitive inhibitors. The in vivo test demonstrated that the peptides harm the survival and development of A. gemmatalis larvae.

Conclusion: These results suggest that these peptides are potential candidates in the management of A. gemmatalis larvae and provide baseline information for the design of new trypsin-like inhibitors based on peptidomimetic tools. © 2020 Society of Chemical Industry.