Spectroscopic Studies and Docking Methods on the Interaction of putrescine with α-Amylase

amylase (a-1,4glucan-4-glucanohydrolase, EC 3.2.1.1) is an endoglycosidase, which hydrolyzes starch molecules to give various products including dextrin and progressively smaller polymers composed of glucose units. α-amylase are glycoside hydrolases and have been classified in family 13. Microbial enzymes are widely used in industrial processes. One of the most important industrial enzymes is α-amylase. This enzyme having applications in industrial processes such as brewing, baking, textiles, pharmaceuticals, starch processing, and detergents. Polyamines are low molecular weight aliphatic polyamines essential for cell growth, differentiation, and proliferation processes. Polyamines such as putrescine are essential for survival. In this study, the interaction between putrescine and α-amylase was investigated by the method of UV-Vis spectroscopy, fluorescence spectroscopy and molecular docking at the temperatures of 318 K and 328 K in pH 6.9 using sodium phosphate as a buffer. The analysis of UV-Vis indicates that by increasing concentration of putrescine, absorption increased. The results of fluorescence spectroscopic measurements suggested that putrescine has a vigorous ability to quench the intrinsic fluorescence of α -amylase through the static quenching procedure. The Stern-Volmer quenching constants (Ksv) for the α-amylase putrescine complex were obtained at two temperatures. The thermodynamic parameters, Gibbs free-energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) changes, displayed that the binding process was spontaneous. The value of n was approximately equal to 1, indicating that there was one single binding site in α-amylase for putrescine during their interaction. Molecular docking results also revealed the presence of one binding site with a negative value for the Gibbs free energy for α –amylase. Further, the docking study revealed that electrostatic bonds played a major role in stabilizing the complex.