Inhibition of digestive trypsins by plant Kunitz proteins reduces the viability of Spodoptera cosmioides larvae

The acquired resistance by insects and the harmful environmental effects of chemical pesticides have encouraged the search of new tools for proper pest management. Among them, the use of protease inhibitors (PIs) obtained from plants has gained interest because they are a natural system against herbivory, are organic molecules with higher specificity and have the potential to cause less damage to nature. The aim of this work was to characterise the inhibitory potential of the proteins ApTI (Adenanthera pavonina trypsin inhibitor) and ILGA (Inga laurina trypsin inhibitor) on the digestive trypsins of Spodoptera cosmioides through molecular docking, enzymatic kinetics and biological survival analyses. The docking between trypsins and inhibitors was performed using the program CLUSPRO; the inhibitory constant Ki and the inhibition type were determined through chromogenic assays. In order to analyse survival, several concentrations of ApTI and ILTI inhibitors were included in the artificial diet of neonatal larvae. In this study, we determined that ILTI binds to the active site of the trypsins with a specificity similar to its natural substrate, whereas APTI showed that the inhibitor reactive site is not in contact with the trypsins catalytic site. The ILTI and APTI inhibitors were characterized as competitive and uncompetitive tight‐binding inhibitors, respectively. The survival curves obtained using Kaplan–Meier estimators indicated that the lowest percentage survival (20%) for all inhibitors tested was obtained using 1.0% doses at a development time of less than 20 days. We concluded that ILTI and APTI present biotechnological potential as agents against phytophagous Lepidoptera insects, inhibiting trypsins through tight‐binding inhibition, with competitive and non‐competitive mechanisms, respectively. The effect of ApTI and ILTI on the development of S. cosmioides larvae is shown to be toxic.