Interaction enthalpies of α-chymotrypsin with water-acetone mixtures

Abstract

© 2017 by Nova Science Publishers, Inc. All rights reserved. The aim of our investigation is to provide a thermochemical description of the stabilizing/destabilizing effects of organic solvents on the enzyme stability to elucidate what intermolecular processes produce the main effect on the stability and functions of the enzymes at low, intermediate, and high water content in organic liquids. Bovine pancreatic A-chymotrypsin was utilized as a model enzyme. Isothermal calorimetry measurements were performed to study the stability of A-chymotrypsin in water-acetone mixtures. Interaction enthalpies of A-chymotrypsin with water-acetone mixtures have been measured at 250C. Our results clearly show that isothermal calorimetry is an effective experimental tool for studying the simultaneous action of water and organic liquids on the stability of enzyme macromolecules. Thermochemical results were compared with the enzyme activity data. The degree of stabilization/destabilization of achymotrypsin depends significantly on the water content in acetone. There are three concentration regimes. At high water content, the residual enzyme activity values are close to 100%. At intermediate water content, residual enzyme activity is close to zero. The residual catalytic activity in the water-poor acetone is ~80%.