Noncovalent interactions of bovine trypsin with curcumin and effect on stability, structure, and function

The structural studies of trypsin with curcumin in Tris-hydrochloride (Tris-HCl) buffer solution (pH 8.0) was explored by UV-vis spectroscopic and fluorescence quenching method, kinetic reaction, circular dichroism (CD), Thermal denaturation, molecular docking, and molecular dynamic simulation. The curcumin could decrease trypsin absorbance. It was showed that curcumin could quench the fluorescence of trypsin by static quenching mechanism. This is in agreement with UV-vis results and CD studies in which the α-helix becomes more, and β-sheet becomes less than trypsin without ligand. The binding constant, the number of binding sites and thermodynamic parameters (ΔH°, ΔS°, and ΔG°) at two temperatures were calculated. The hydrogen bond and Van der Waals interaction were found as the main forces, which is in congruence with docking results. The outcome of the kinetic reaction indicates an uncompetitive inhibition by curcumin on trypsin. Molecular Dynamic simulation and Thermal denaturation results demonstrate that curcumin makes trypsin unstable and more flexible.