Evaluation of interaction between citrus flavonoid, naringenin, and pepsin using spectroscopic analysis and docking simulation

Abstract

Pepsin is an aggressive proteolytic enzyme in the gastric contents that are released by the primary cells and breaks down food proteins into peptides. Naringenin (NG) is a flavonoid that is usually consumed by humans and has beneficial health effects. The present paper depicts the possible impact of NG on the pepsin structure and its mechanisms of action. It was found that absorbance increases at 280 nm by UV–Vis technique might be ascribed to the pepsin-NG complexes formation. The fluorescence spectroscopic demonstrated that the NG could quench the pepsin (with the static mechanism) intrinsic fluorescence. Besides, thermodynamic parameters indicated that an essential role in the binding of the complex is mainly hydrophobic forces. The pepsin stability declined in the absence and presence of various naringenin concentrations, which agrees with MD simulation results; and from CD studies at high concentrations of NG, unfolding of the protein with a reduction in the α-helix (10.0% to 8.2%) and an increase in β-sheet (38.3% to 43.0%). The naringenin-pepsin complex uncovered an average RMSD (1.34 nm) more than that of the free pepsin system (1.33 nm), which agreed with the finding of thermal stability. RMSF results show that the protein structure gains more rigidity. Kinetic studies showed that the activity of the enzyme was decreased.