A short, strong hydrogen bond in the active site of human carbonic anhydrase II

The crystal structure characterization of human carbonic anhydrase II (HCA II) is obtained at 0.9 [Angstrom] resolution to reveal a water molecule, termed deep water, Dw, bound in a hydrophobic pocket of the active site that forms a short, strong hydrogen bond with the zinc-bound solvent molecule. The short, strong hydrogen bond formed is expected to contribute to the low p[K.sub.a] of the zinc-bound water and to promote proton transfer in catalysis.