In vitro assessment of phthalate acid esters-trypsin complex formation

•The interactions between PAEs and the trypsin are studied in vitro.•Multi-spectroscopic techniques and molecular docking are used.•The affinity order of DMP > DEP > DBP is opposite to the side-chain length order.•The effect of PAEs on the trypsin construction is studied.

In this work, interactions of three phthalate acid esters (PAEs), including dimethyl phthalate (DMP), diethyl phthalate (DEP) and dibutyl phthalate (DBP), with trypsin have been studied in vitro, under simulated physiological conditions using multi-spectroscopic techniques and molecular modeling. The results show that these PAEs can bind to the trypsin, forming trypsin-PAEs complexes, mainly via hydrophobic interactions, with the affinity order of DMP > DEP > DBP. Binding to the PAEs is found to result in molecular deformation of trypsin. The modeling results suggest that only DBP can bind with the amino acid residues of the catalytic triad and S1 binding pocket of trypsin, leading to potential competitive enzyme inhibition.

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