Open AccessStructural and kinetic insights into the mechanism of 5‐hydroxyisourate hydrolase from Klebsiella pneumoniae
Author(s) -
French Jarrod B.,
Ealick Steven E.
Publication year - 2011
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s090744491101746x
Subject(s) - active site , hydrolase , klebsiella pneumoniae , chemistry , enzyme , stereochemistry , structural similarity , biochemistry , escherichia coli , gene
The stereospecific oxidative degradation of uric acid to ( S )‐allantoin has recently been demonstrated to proceed via two unstable intermediates and requires three separate enzymatic reactions. The second step of this reaction, the conversion of 5‐hydroxyisourate (HIU) to 2‐oxo‐4‐hydroxy‐4‐carboxy‐5‐ureidoimidazoline, is catalyzed by HIU hydrolase (HIUH). The high‐resolution crystal structure of HIUH from the opportunistic pathogen Klebsiella pneumoniae (KpHIUH) has been determined. KpHIUH is a homotetrameric protein that, based on sequence and structural similarity, belongs to the transthyretin‐related protein family. In addition, the steady‐state kinetic parameters for this enzyme and four active‐site mutants have been measured. These data provide valuable insight into the functional roles of the active‐site residues. Based upon the structural and kinetic data, a mechanism is proposed for the KpHIUH‐catalyzed reaction.