Water networks in fast proton transfer during catalysis by human carbonic anhydrase II.

ABSTRACT: Variants of human carbonic anhydrase II (HCA II) with amino acid replacements at residues in contact with water molecules in the active-site cavity have provided insights into the proton transfer rates in this protein environment. X-ray crystallography and (18)O exchange measured by membrane inlet mass spectrometry have been used to investigate structural and catalytic properties of variants of HCA II containing replacements of Tyr7 with Phe (Y7F) and Asn67 with Gln (N67Q). The rate constants for transfer of a proton from His64 to the zinc-bound hydroxide during catalysis were 4 and 9 μs(-1) for Y7F and Y7F/N67Q, respectively, compared with a value of 0.8 μs(-1) for wild-type HCA II. These higher values observed for Y7F and Y7F/N67Q HCA II could not be explained by differences in the value

SUBMITTER: Mikulski R 

PROVIDER: S-EPMC3540201 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature