a thermodynamic study of the interaction between urease and copper ions

a thermodynamic study of copper ions by jack bean urease (jbu) was carried out at two temperatures of 27 and 37?c in tris buffer (30 mm; ph=7.0) using an isothermal titration calorimetry. there is a set of twelve identical and non-interacting binding sites for copper ions. the intrinsic dissociation equilibrium constant and the molar enthalpy of binding are 285 µm and ?15.2 kj/mol at 27?c and 346 µm and ?14.6 kj/mol at 37?c, respectively. the molar entropy of binding is ?17.2 j k-1 mol-1at 27?c and +19.1 j k-1 mol-1 at 37?c. hence, the binding process of copper ion to jbu is not only enthalpy driven but also it is entropy driven, which the role of entropy driven should be more effective by increasing the temperature.