The Interaction of Ferric Ions with Jack Bean Urease by Isothermal Titration Calorimetry

The aim of the investigations was to measure the influence of Fe3+ ion on jack bean urease (JBU) activity. Interaction between Fe3+ and JBU, is examined using isothermal titration calorimetry. It was found that Fe3+ ions acted as a non-cooperative inhibitor of JBU, and there is a set of 12 identical and independent binding sites for Fe3+ ions. The small structural parameters show that there are little changes on the JBU structure, indicating that Fe3+ has minor effect on the JBU activity. The association equilibrium constant is 42,484.13 +/- A 110 mol l(-1), indicating the moderate interaction of Fe3+ ion with JBU. The molar enthalpy of binding is Delta H = -4.33 kJ mol(-1).