Spectroscopy and molecular docking study on the interaction behavior between nobiletin and pepsin

In this study, the binding mode of nobiletin (NOB) with pepsin was investigated by spectroscopic and molecular docking methods. NOB can interact with pepsin to form a NOB-pepsin complex. The binding constant, number of binding sites and thermodynamic parameters were measured, which indicated that NOB could spontaneously bind with pepsin through hydrophobic and electrostatic forces with one binding site. Molecular docking results revealed that NOB bound into the pepsin cavity. Synchronous and three-dimensional fluorescence spectra results provide data concerning conformational and some micro-environmental changes of pepsin. Furthermore, the binding of NOB can inhibit pepsin activity in vitro. The present study provides direct evidence at a molecular level to show that NOB could induce changes in the enzyme pepsin structure and function.