Arginine-containing dipeptides decrease affinity of gut trypsins and compromise soybean pest development

The design and production of molecules capable of mimicking the binding or/and functional sites of proteins inhibitors represent a promising strategy for the exploration and modulation of gut trypsin function in insect pests, specifically Lepidoptera. Here, for the first time, we characterized the trypsin activity present in the gut, performance and development of Anticarsia gemmatalis (Lepidoptera: Noctuidae) larvae when exposed to arginine-containing dipeptides. In silico assessment showed that arginine-containing dipeptides have a greater affinity for the active site of A. gemmatalis trypsins than lysine-containing peptides due to the presence of the double-charged guanidinium group that enhances the interaction at the S1 subsite of trypsins. Furthermore, the inhibitory and anti-insect potential of the peptides was demonstrated through kinetic and larval life cycle parameters, respectively. These dipeptides showed structural stability, binding to the active site, corroborated in vitro (competitive inhibition), and significant reduction of trypsin enzyme activity in the gut, survival, and weight of the A. gemmatalis larvae. Our findings reinforce the idea that small peptides are promising candidates for lepidopteran pest management. The optimization of DI2 and DI1 peptides, enhancing uptake and affinity to trypsins, may turn the use of these molecules feasible in agriculture.