Near-atomic resolution structures of urate oxidase complexed with its substrate and analogues: the protonation state of the ligand.
Acta Crystallogr D Biol Crystallogr
; 66(Pt 6): 714-24, 2010 Jun.
Article
em En
| MEDLINE
| ID: mdl-20516624
ABSTRACT
Urate oxidase (uricase; EC 1.7.3.3; UOX) from Aspergillus flavus catalyzes the oxidation of uric acid in the presence of molecular oxygen to 5-hydroxyisourate in the degradation cascade of purines; intriguingly, catalysis proceeds using neither a metal ion (Fe, Cu etc.) nor a redox cofactor. UOX is a tetrameric enzyme with four active sites located at the interface of two subunits; its structure was refined at atomic resolution (1 A) using new crystal data in the presence of xanthine and at near-atomic resolution (1.3-1.7 A) in complexes with the natural substrate (urate) and two inhibitors 8-nitroxanthine and 8-thiouric acid. Three new features of the structural and mechanistic behaviour of the enzyme were addressed. Firstly, the high resolution of the UOX-xanthine structure allowed the solution of an old structural problem at a contact zone within the tetramer; secondly, the protonation state of the substrate was determined from both a halochromic inhibitor complex (UOX-8-nitroxanthine) and from the H-atom distribution in the active site, using the structures of the UOX-xanthine and the UOX-uric acid complexes; and thirdly, it was possible to extend the general base system, characterized by the conserved catalytic triad Thr-Lys-His, to a large water network that is able to buffer and shuttle protons back and forth between the substrate and the peroxo hole along the reaction pathway.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Prótons
/
Aspergillus flavus
/
Urato Oxidase
/
Ácido Úrico
Idioma:
En
Revista:
Acta Crystallogr D Biol Crystallogr
Ano de publicação:
2010
Tipo de documento:
Article
País de afiliação:
França