Biophysical and Structural Insights in α-Amylase and Bile Acids interaction

Abstract

Amylase is an enzyme exposed to the effect of bile acids (BAs) in intestine. BAs may potential reduce the activity of the enzyme. In this paper, an insight in biophysical and structural terms on how taurodeoxycholic and deoxycholic acids (TDCA and DCA, respectively) interact with α-amylase is given, using UV-visible, fluorescence and infrared spectroscopy (FTIR), electron microscopy, dynamic light scattering (DLS) and molecular docking calculations. Fluorescence spectroscopy measurements, confirm that TDCA and DCA interact with α-amylase with high affinity causing conformational changes. Also, DCA significantly modify the thermal denaturation of the protein. Besides, DCA induces a decrease in α-helix and unordered region, together with an important increase in β-sheet, modifying the surface charges of the protein and inducing the formation of protein aggregates producing a loss of activity. Docking results indicate that TDCA interacts with the surface of the enzyme, while DCA may stabilize inside the active site of α-amylase thereby justifying its inhibitory mechanism. BAs acts as protein-unfolding agents and the mechanism is dependent on the structure of the bile acid under study. These findings provide a deeper understanding of the interaction of BAs with proteins and its role as protein-unfolding agents, at molecular level.