Peptidic product derived from trypsin autolysis modulates insect digestive proteases and supports plant biochemical defense

Abstract BACKGROUND Spodoptera frugiperda , commonly known as the fall armyworm, is a highly economically significant pest that affects various crops, resulting in substantial losses in productivity. Managing this pest primarily relies on chemical insecticides; however, the repeated development of resistance to these chemicals has rendered them less effective. Given this scenario, sustainable alternatives, such as the use of digestive enzyme inhibitors, have been investigated as potential tools in pest management. RESULTS Molecular docking predicts a conserved, isoform‐spanning pose for GORE 3 on S. frugiperda trypsins, with occupancy of S1/S1′ and adjacent subsites and richer aromatic/hydrophobic contacts than the S1‐focused reference benzamidine. This binding topology aligns with the enzymology: GORE 3 acts as a competitive inhibitor (K i = 4.00 mM) versus benzamidine (K i = 1.64 mM), and IC 50 determinations confirmed effective enzymatic blockade. In vivo , GORE 3 reduced larval body mass, extended the larval period, and produced mortality up to 46.66%. Nutritional and kinetic parameters were significantly affected, including increased K M (reduced substrate affinity) and lower approximate digestibility at higher dietary levels. Despite these effects, neither the leaf area consumed nor the feeding preference index differed from those of the controls. CONCLUSION Docking and bioassays collectively demonstrate that GORE 3 interacts with trypsin‐ like proteases through a robust, multisite binding mode, resulting in competitive inhibition and measurable physiological effects in S. frugiperda . Although less potent than benzamidine based on K i values, GORE3's isoform‐spanning interactions and its influence on digestive and developmental parameters highlight the relevance of studying protease‐inhibitor peptides as biochemical models for understanding lepidopteran digestive physiology. Future work should investigate peptide stability, compensatory digestive responses, and performance under diverse biological conditions to better clarify the biological significance of these interactions. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.