The interaction of the green tea polyphenol (catechin) with pepsin: Insights from spectroscopic to molecular dynamics studies

Abstract Pepsin is an aspartic proteinase that plays an essential role in controlling many biological processes, therapy, and pharmaceutical research. Catechins belong to the group of polyphenols that are the most basic chemical composition of green tea. If catechin gets into the human stomach, the binding targets may be the digestive protease. This paper focuses on the behavior of the pepsin enzyme onto the green tea polyphenol, (+)-catechin hydrate. The effects of catechin hydrate on the structure and activity of pepsin were done utilizing ultraviolet−visible (UV–Vis) spectroscopy, intrinsic fluorescence spectroscopy, circular dichroism (CD), thermal stability, kinetic techniques, as well as molecular docking, and Molecular dynamic simulations (MD) technique. The experimental results from fluorescence spectroscopy revealed that the alterations in pepsin's tertiary structure were caused by catechin hydrate binding. The apparent binding constant Ka, the number of binding sites, and thermodynamic parameters were calculated at three different temperatures. Thermodynamic results revealed that catechin hydrate interacts with pepsin spontaneously by hydrophobic forces. The result of the circular dichroism spectral suggests the secondary structural changes. An increase in the content of the β-turn structure was shown. Kinetic parameters revealed that catechin hydrate inhibited the activity of pepsin. The Molecular dynamic (MD) and docking simulations supported experimental findings. As a result, catechin hydrate could be considered as an inhibitor with adverse effects on pepsin structure and function.