Structural and Mechanistic Studies on Klebsiella pneumoniae 2-Oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline Decarboxylase.
Summary of "Structural and Mechanistic Studies on Klebsiella pneumoniae 2-Oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline Decarboxylase."
The stereospecific oxidative degradation of uric acid to (S)-allantoin was recently shown to proceed via three enzymatic steps. The final conversion is a decarboxylation of the unstable intermediate 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU) and is catalyzed by OHCU decarboxylase. Here we present the structures of Klebsiella pneumoniae OHCU decarboxylase in unliganded form and with bound allantoin. These structures provide evidence that ligand binding organizes the active site residues for catalysis. Modeling of the substrate and intermediates provides additional support for this hypothesis. In addition we characterize the steady state kinetics of this enzyme and report the first OHCU decarboxylase inhibitor, allopurinol, a structural isomer of hypoxanthine. This molecule is a competitive inhibitor of K. pneumoniae OHCU decarboxylase with a K(i) of 30 ± 2 μm. Circular dichroism measurements confirm structural observations that this inhibitor disrupts the necessary organization of the active site. Our structural and biochemical studies also provide further insights into the mechanism of catalysis of OHCU decarboxylation.
Affiliation
From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853.
Journal Details
This article was published in the following journal.
Name: The Journal of biological chemistry
ISSN: 1083-351X
Pages: 35446-54
Links
- PubMed Source: http://www.ncbi.nlm.nih.gov/pubmed/20826786
- DOI: http://dx.doi.org/10.1074/jbc.M110.156034
Medical and Biotech [MESH] Definitions
3-isopropylmalate Dehydrogenase
An NAD+ dependent enzyme that catalyzes the oxidation of 3-carboxy-2-hydroxy-4-methylpentanoate to 3-carboxy-4-methyl-2-oxopentanoate. It is involved in the biosynthesis of VALINE; LEUCINE; and ISOLEUCINE.
Klebsiella Pneumoniae
Gram-negative, non-motile, capsulated, gas-producing rods found widely in nature and associated with urinary and respiratory infections in humans.
Enterobacter Aerogenes
Gram-negative, capsulated, gas-producing rods found widely in nature. Both motile and non-motile strains exist. The species is closely related to KLEBSIELLA PNEUMONIAE and is frequently associated with nosocomial infections
Klebsiella Infections
Infections with bacteria of the genus KLEBSIELLA.
2-hydroxy-5-nitrobenzyl Bromide
A chemical reagent that reacts with and modifies chemically the tryptophan portion of protein molecules. Used for 'active site' enzyme studies and other protein studies. Sometimes referred to as Koshland's reagent.
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