In vitro and in silico evaluation of inhibitory effects of bisphenol derivatives on acetylcholinesterase of electric eel (Electrophorus electricus L.)

The inhibitory effects of bisphenol A (BPA) and bisphenol S (BPS), which are common pollutants, especially in marine and freshwater, on the electric eel acetylcholinesterase (AChE) activity were studied in vitro and in silico. Both produced full non-competitive inhibition, but the Ki value of BPA was half that of BPS. Molecular docking analyses revealed that both interact with residues W286, F297, Y337, F338 in the PAS and ABS regions in the middle and entrance of the active site gorge, and that BPS also has hydrogen bond with S203 of the catalytic triad. The surge at IC50 values of both compounds with an inflection point at pH: 8.2 suggested that Y124 and/or Y337 in the narrow gorge are primary structural factors in binding. Less effective inhibition of BPS, especially at 25-30 degrees C, the temperature at which enzyme activity peaks, was attributed to the conformation of the narrow gorge. Homology analyses for AChE initially revealed a significant degree of identity, particularly in the alpha/ beta hydrolase domain, which also comprises the active site, with sequences from seven distinct teleost species of various environments. Finally, it was discovered for the first time that BPS, like BPA, is a significant inhibitor of AChE, and this was confirmed by in vitro and in silico analyses done at various pH and temperature levels. It was concluded that this effect might also apply to AChE of most other bony fish.