Interaction behavior between myricetin and dihydromyricetin with pepsin by spectroscopic and docking methods

The effect of myricetin (MY) and dihydromyricetin (DMY) on the activity of pepsin was evaluated. The interaction between MY and DMY with pepsin was investigated using multispectroscopic and molecular docking methods. Binding constant, number of binding sites, and thermodynamic parameters at different temperatures were measured. MY and DMY have no significant effect on the activity of pepsin. The results of fluorescence quenching revealed that MY and DMY could strongly quench the intrinsic fluorescence of pepsin through a static quenching procedure. The thermodynamic parameters showed that hydrophobic interactions played main roles in the interaction of MY with pepsin, while the Van der Waals' interactions and hydrogen bonds were mainly interactions between DMY and pepsin. The analysis of UV absorption spectra and molecular docking showed that MY and DMY induced conformational changes of pepsin. The synchronous fluorescence spectra indicated that microenvironment around tyrosine and tryptophan residues of pepsin were not changed obviously. The energy transfer from pepsin molecules to MY or DMY occurs with high probability. Displacement experiments indicated that DMY and MY could bind to the same site of pepsin.