A novel acetate-bound complex of human carbonic anhydrase II.

The enzyme human carbonic anhydrase II (hCAII) crystallized in an acetate-bound complex belonging to space group P2(1)2(1)2(1), with unit-cell parameters a = 42.3, b = 71.8, c = 74.0 A. The structure was solved by the molecular-replacement method and refined to an R value of 0.18 and an R(free) of 0.21. The acetate molecule replaced the zinc-bound water molecule in the structure, differing from previous reports regarding the site of acetate binding. This mode of binding disrupts the hydrogen-bonded solvent network required for activity of the enzyme. This mode of inhibitor binding is a novel one that has not been observed previously.