Thermodynamic study of CN− ion inhibition of Jack bean urease using the extended solvation theory

Cyanide ion was studied as an inhibitor of Jack bean urease at 300 K in 30 mmol/L tris buffer, pH 7. The inhibition was investigated by isothermal titration calorimetry (ITC). The extended solvation model was used for CN− + JBU interaction over the whole range of CN− concentrations. The binding parameters recovered from the solvation model were attributed to the cyanide ion interaction. It was found that cyanide ion acted as a non-cooperative inhibitor of urease, and there is a set of 12 ± 0.12 identical and independent binding sites for CN− ions. The dissociation equilibrium constant is 749.99 μmol/L. The molar enthalpy of binding is ΔH = −13.60 kJ mol−1.