2Q37
Crystal structure of OHCU decarboxylase in the presence of (S)-allantoin
Summary for 2Q37
| Entry DOI | 10.2210/pdb2q37/pdb |
| Descriptor | OHCU decarboxylase, 1-[(4S)-2,5-DIOXOIMIDAZOLIDIN-4-YL]UREA (3 entities in total) |
| Functional Keywords | ohcu, 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline, plant protein, lyase |
| Biological source | Arabidopsis thaliana (thale cress) |
| Cellular location | Cell membrane; Peripheral membrane protein: Q9LVM5 |
| Total number of polymer chains | 1 |
| Total formula weight | 20995.28 |
| Authors | |
| Primary citation | Kim, K.,Park, J.,Rhee, S. Structural and functional basis for (s)-allantoin formation in the ureide pathway. J.Biol.Chem., 282:23457-23464, 2007 Cited by PubMed Abstract: The ureide pathway, which mediates the oxidative degradation of uric acid to (S)-allantoin, represents the late stage of purine catabolism in most organisms. The details of uric acid metabolism remained elusive until the complete pathway involving three enzymes was recently identified and characterized. However, the molecular details of the exclusive production of one enantiomer of allantoin in this pathway are still undefined. Here we report the crystal structure of 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline (OHCU) decarboxylase, which catalyzes the last reaction of the pathway, in a complex with the product, (S)-allantoin, at 2.5-A resolution. The homodimeric helical protein represents a novel structural motif and reveals that the active site in each monomer contains no cofactors, distinguishing this enzyme mechanistically from other cofactor-dependent decarboxylases. On the basis of structural analysis, along with site-directed mutagenesis, a mechanism for the enzyme is proposed in which a decarboxylation reaction occurs directly, and the invariant histidine residue in the OHCU decarboxylase family plays an essential role in producing (S)-allantoin through a proton transfer from the hydroxyl group at C4 to C5 at the re-face of OHCU. These results provide molecular details that address a longstanding question of how living organisms selectively produce (S)-allantoin. PubMed: 17567580DOI: 10.1074/jbc.M703211200 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (2.5 Å) |
Structure validation
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