Mechanistic insights into pyrethroid binding: conformational and functional effects of deltamethrin on lysozyme

Deltamethrin, a pyrethroid pesticide considered low to moderately toxic, may pose risks even at low exposure levels. However, its effects on human proteins remain poorly understood. In this study, we investigated the interaction between deltamethrin (DLM) and human lysozyme (HuL), a key innate immune enzyme and model protein for misfolding and aggregation, using integrated in-vitro and in-silico approaches. DLM binds both native and misfolded states of HuL with association constants of 3.74 × 10⁴ M^-1 and 2.53 × 10⁴ M^-1, respectively. Molecular docking study predicts that DLM binds near catalytic site of HuL via hydrogen bonds and hydrophobic interactions. Simulation of HuL and HuL:DLM complexes was carried out at two temperatures, i.e. 298.15 and 338.15 K. The results showed that DLM-binding induces only modest conformational flexibility without significant destabilization. Also, in-vitro studies showed that DLM binding has no major effect on the overall conformation and stability of HuL, although minor modulation in microenvironmental dynamics was observed. Temperature and pH induced aggregation of HuL were also studied, and results showed that DLM did not promote aggregation and only caused a marginal change under specific conditions. The study showed that DLM-binding slightly enhanced the catalytic activity of HuL, indicating subtle functional modulation rather than destabilization. Overall, DLM binds efficiently to HuL and induces subtle structural and functional changes without affecting stability or aggregation. Notably, its ability to modulate HuL's microenvironment and catalytic activity highlights the potential of protein-level perturbations as potential early biomarkers of pesticide exposure.