View source for 3qvj


==Allantoin racemase from Klebsiella pneumoniae==
<StructureSection load='3qvj' size='340' side='right'caption='[[3qvj]], [[Resolution|resolution]] 2.10&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[3qvj]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Klebsiella_pneumoniae_subsp._pneumoniae_MGH_78578 Klebsiella pneumoniae subsp. pneumoniae MGH 78578]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=3QVJ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=3QVJ FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.1&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=MSE:SELENOMETHIONINE'>MSE</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=3qvj FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=3qvj OCA], [https://pdbe.org/3qvj PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=3qvj RCSB], [https://www.ebi.ac.uk/pdbsum/3qvj PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=3qvj ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/A6T9E8_KLEP7 A6T9E8_KLEP7] 
<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The oxidative catabolism of uric acid produces 5-hydroxyisourate (HIU), which is further degraded to (S)-allantoin by two enzymes, HIU hydrolase and 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline decarboxylase. The intermediates of the latter two reactions, HIU and 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline, are unstable in solution and decay nonstereospecifically to allantoin. In addition, nonenzymatic racemization of allantoin has been shown to occur at physiological pH. Since the further breakdown of allantoin is catalyzed by allantoinase, an enzyme that is specific for (S)-allantoin, an allantoin racemase is necessary for complete and efficient catabolism of uric acid. In this work, we characterize the structure and activity of allantoin racemase from Klebsiella pneumoniae (KpHpxA). In addition to an unliganded structure solved using selenomethionyl single-wavelength anomalous dispersion, structures of C79S/C184S KpHpxA in complex with allantoin and with 5-acetylhydantoin are presented. These structures reveal several important features of the active site including an oxyanion hole and a polar binding pocket that interacts with the ureido tail of allantoin and serves to control the orientation of the hydantoin ring. The ability of KpHpxA to interconvert the (R)- and (S)-enantiomers of allantoin is demonstrated, and analysis of the steady-state kinetics of KpHpxA yielded a k(cat)/K(m) of 6.0x10(5) M(-1) s(-1). Mutation of either of the active-site cysteines, Cys79 or Cys184, to serine inactivates this enzyme. The data presented provide new insights into the activity and substrate specificity of this enzyme and enable us to propose a mechanism for catalysis that is consistent with the two-base mechanism observed in other members of the aspartate/glutamate family.

Characterization of the Structure and Function of Klebsiella pneumoniae Allantoin Racemase.,French JB, Neau DB, Ealick SE J Mol Biol. 2011 May 17. PMID:21616082<ref>PMID:21616082</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 3qvj" style="background-color:#fffaf0;"></div>
== References ==
<references/>
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</StructureSection>
[[Category: Klebsiella pneumoniae subsp. pneumoniae MGH 78578]]
[[Category: Large Structures]]
[[Category: Ealick SE]]
[[Category: French JB]]
[[Category: Neau DB]]