Mechanism of inactivation of Escherichia coli aspartate aminotransferase by (S)-4-amino-4,5-dihydro-2-furancarboxylic acid .

ABSTRACT: As a potential drug to treat neurological diseases, the mechanism-based inhibitor (S)-4-amino-4,5-dihydro-2-furancarboxylic acid (S-ADFA) has been found to inhibit the ?-aminobutyric acid aminotransferase (GABA-AT) reaction. To circumvent the difficulties in structural studies of a S-ADFA-enzyme complex using GABA-AT, l-aspartate aminotransferase (l-AspAT) from Escherichia coli was used as a model PLP-dependent enzyme. Crystal structures of the E. coli aspartate aminotransferase with S-ADFA bound to the active site were obtained via cocrystallization at pH 7.5 and 8. The complex structures suggest that S-ADFA inhibits the transamination reaction by forming adducts with the catalytic lysine 246 via a covalent bond while producing 1 equiv of pyridoxamine 5'-phosphate (PMP). Based on the structures, formation of the K246-S-ADFA adducts requires a specific initial binding configuration of S-ADFA in the l-AspAT active site, as well as deprotonation of the ?-amino group of lysine 246 after the formation of the quinonoid and/or ketimine intermediate in the overall inactivation reaction.

SUBMITTER: Liu D 

PROVIDER: S-EPMC3013228 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature