Characterization of nickel(II) bovine carbonic anhydrase and its inhibitor derivatives

The nickel(II) derivative of carbonic anhydrase and its adducts with inhibitors have been investigated through electronic and nuclear magnetic resonance (nmr) spectroscopy. The metal ion in the pure enzyme is six-coordinated, and there is evidence for at least one water molecule in the coordination sphere. Inhibitors replace the water molecule, still giving rise to six-coordinated adducts. The affinity of the inhibitors is decreased at alkaline pH but cannot be related to a single ionization in the active site cavity.