The cyanide ion was studied as an effecter of Jack bean urease at 300 K in 30 mmol⋅L−1 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 interaction with cyanide ion. It was found that cyanide ion acted as a noncooperative inhibitor of urease, and there is a set of 12 identical and independent binding sites for CN− ions. The dissociation equilibrium constant is 749.99 μmol⋅L−1. The molar enthalpy of binding is ΔH=−13.60 kJ⋅mol−1.