A thermodynamic study on the interaction of bovine carbonic anhydrase II, CAII, with cobalt(II) and iron(III) ions was made using isothermal titration calorimetry (ITC) at 300.15 K and 310.15 K in Tris buffer solutions at pH = 7.5. The enthalpies of interaction of Co 2+ + CAII and Fe 3+ + CAII are reported and analyzed in terms of the extended solvation theory. The results indicate that there are three identical and non-cooperative binding sites for Co 2+ and Fe 3+ ions. Binding of these ions with CAII occurs exothermically with dissociation equilibrium constants of 87.15 and 91.00 µmol·L −1 at 300.15 K, for Co 2+ and Fe 3+ , respectively.

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