A Thermodynamic Study on the Binding of Cobalt(II) and Iron(III) Ions with Bovine Carbonic Anhydrase II at Different Temperatures

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 Co2++ CAII and Fe3++ 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 Co2+ and Fe3+ 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 Co2+ and Fe3+, respectively.