Multi-approach study on diethylhexyl phthalate and monoethylhexyl phthalate binding to lysozyme: In silico, bioactivity and surface plasmon resonance analyses

Diethylhexyl phthalate (DEHP) and its metabolite monoethylhexyl phthalate (MEHP) are recognized as endocrine disruptors with significant toxicological effects on various human physiological systems. While previous research has explored phthalate-protein interactions, there is a notable gap in studies focusing on the interaction between these endocrine disruptors and lysozyme (L_ZM), a critical component of the immune system. This study aimed to investigate the interactions of DEHP and MEHP with chicken egg white lysozyme (CEWL_ZM) using molecular docking, molecular dynamics simulations, bioactivity and surface plasmon resonance (SPR) analyses to evaluate the molecular mechanisms, binding affinity, kinetic properties and bioactivity effects of these interactions. Complementary insights from molecular docking and molecular dynamics simulations indicate that DEHP has a stronger binding affinity for CEWL_ZM than MEHP. This affinity value was corroborated by an intense hydrophobic and van der Waals interaction network especially maintained by the active residue Leu75 and Asp101-Ala107. Although MEHP did not exhibit a significant effect on enzyme activity in lysozyme bioactivity assay, DEHP inhibited lysozyme with an IC₅₀ value of 453 µM. SPR analysis revealed that DEHP exhibits a significantly stronger binding affinity to CEWL_ZM compared to MEHP.