Structural and mutational analysis of Trypanosoma brucei prostaglandin H2 reductase provides insight into the catalytic mechanism of aldo-ketoreductases.
J Biol Chem
; 280(28): 26371-82, 2005 Jul 15.
Article
em En
| MEDLINE
| ID: mdl-15845552
ABSTRACT
Trypanosoma brucei prostaglandin F2alpha synthase is an aldo-ketoreductase that catalyzes the reduction of prostaglandin H2 to PGF2alpha in addition to that of 9,10-phenanthrenequinone. We report the crystal structure of TbPGFS.NADP+.citrate at 2.1 angstroms resolution. TbPGFS adopts a parallel (alpha/beta)8-barrel fold lacking the protrudent loops and possesses a hydrophobic core active site that contains a catalytic tetrad of tyrosine, lysine, histidine, and aspartate, which is highly conserved among AKRs. Site-directed mutagenesis of the catalytic tetrad residues revealed that a dyad of Lys77 and His110, and a triad of Tyr52, Lys77, and His110 are essential for the reduction of PGH2 and 9,10-PQ, respectively. Structural and kinetic analysis revealed that His110, acts as the general acid catalyst for PGH2 reduction and that Lys77 facilitates His110 protonation through a water molecule, while exerting an electrostatic repulsion against His110 that maintains the spatial arrangement which allows the formation of a hydrogen bond between His110 and C11 that carbonyl of PGH2. We also show Tyr52 acts as the general acid catalyst for 9,10-PQ reduction, and thus we not only elucidate the catalytic mechanism of a PGH2 reductase but also provide an insight into the catalytic specificity of AKRs.
Buscar no Google
Base de dados:
MEDLINE
Assunto principal:
Oxirredutases
/
Trypanosoma brucei brucei
/
Hidroxiprostaglandina Desidrogenases
/
Prostaglandina H2
Limite:
Animals
/
Humans
Idioma:
En
Ano de publicação:
2005
Tipo de documento:
Article