# Synthetic Peptide Inhibition of Trypsin‐Like Proteases in Spodoptera frugiperda (Lepidoptera: Noctuidae): Evaluating the Influence of Gut Microbiota

## TL;DR

Researchers tested synthetic peptides that inhibit digestive enzymes in a major pest insect and found they impair digestion and growth, with limited impact from gut microbiota disruption.

## Contribution

The study introduces two synthetic tripeptides as effective inhibitors of trypsin-like proteases in Spodoptera frugiperda, exploring their efficacy under gut microbiota disruption.

## Key findings

- GORE1 and GORE2 competitively inhibit trypsin-like proteases in S. frugiperda with Ki values of 1.41 mM and 0.49 mM, respectively.
- Peptide treatments reduced nutritional indices and larval body mass, with GORE1 impairing growth even when gut microbiota was disrupted.
- Microbiota disruption did not significantly alter enzymatic inhibition but modulated developmental responses like prolonged larval growth.

## Abstract

Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) is a major agricultural pest whose control has been increasingly challenged by resistance to conventional insecticides. Synthetic protease inhibitors represent promising alternatives; however, the potential modulation of their efficacy by gut microbiota remains poorly understood. Here, we evaluated two rationally designed synthetic tripeptides, GORE1 and GORE2, as inhibitors of trypsin‐like digestive proteases and investigated whether gut microbiota disruption alters their inhibitory performance in S. frugiperda. Enzymatic assays revealed competitive inhibition patterns, with Ki
values of 1.41 mM for GORE1 and 0.49 mM for GORE2. Most treatments increased apparent KM
values, indicating reduced substrate affinity, whereas GORE2 consistently showed lower KM
values. Despite stronger in vitro affinity (lower Ki
), GORE2 did not produce greater biological impairment than GORE1. Microbiota imbalance induced by antibiotic treatment did not significantly alter larval survival or enzymatic inhibition patterns but modulated specific developmental responses, particularly prolonged larval development and reduced body mass under GORE1 exposure. Nutritional indices (ECI and ECD) were significantly reduced in peptide‐treated larvae, supporting impaired protein metabolism. These findings demonstrate that synthetic peptides effectively inhibit trypsin‐like proteases in S. frugiperda and negatively affect larval nutritional performance. Although microbiota disruption did not modify survival or primary enzymatic inhibition, microbiota‐mediated compensatory mechanisms cannot be excluded. Future integrative studies combining microbiome profiling and metabolic analyses will be essential to resolve host–enzyme–microbiota interactions under digestive inhibition.

Synthetic peptides (GORE1 and GORE2) inhibit trypsin‐like proteases in Spodoptera frugiperda, impairing digestion and nutritional performance. Microbiota disruption did not markedly alter enzymatic inhibition but modulated certain developmental responses. Peptide‐based protease inhibitors show promise for targeted pest management applications.

Peptides GORE1 and GORE2 inhibit midgut trypsin‐like enzymes in Spodoptera frugiperda.Enzyme kinetics confirmed a competitive inhibition mechanism for both peptides.Gut microbiota disruption did not alter peptide inhibitory activity.GORE1 impaired larval growth even under microbiota disruption.Peptide inhibitors are promising complementary tools for integrated pest management.

Peptides GORE1 and GORE2 inhibit midgut trypsin‐like enzymes in Spodoptera frugiperda.

Enzyme kinetics confirmed a competitive inhibition mechanism for both peptides.

Gut microbiota disruption did not alter peptide inhibitory activity.

GORE1 impaired larval growth even under microbiota disruption.

Peptide inhibitors are promising complementary tools for integrated pest management.