Structure of FAD-bound L-aspartate oxidase: insight into substrate specificity and catalysis.
L-Aspartate oxidase (Laspo) catalyzes the conversion of L-Asp to iminoaspartate, the first step in the de novo biosynthesis of NAD(+). This bacterial pathway represents a potential drug target since it is absent in mammals. The Laspo R386L mutant was crystallized in the FAD-bound catalytically competent form and its three-dimensional structure determined at 2.5 A resolution in both the native state and in complex with succinate. Comparison of the R386L holoprotein with the wild-type apoenzyme [Mattevi, A., Tedeschi, G., Bacchella, L., Coda, A., Negri, A., and Ronchi, S. (1999) Structure 7, 745-756] reveals that cofactor incorporation leads to the ordering of two polypeptide segments (residues 44-53 and 104-141) and to a 27 degree rotation of the capping domain. This motion results in the formation of the active site cavity, located at the interface between the capping domain and the FAD-binding domain. The structure of the succinate complex indicates that the cavity surface is decorated by two clusters of H-bond donors that anchor the ligand carboxylates. Moreover, Glu121, which is strictly conserved among Laspo sequences, is positioned to interact with the L-Asp alpha-amino group. The architecture of the active site of the Laspo holoenzyme is remarkably similar to that of respiratory fumarate reductases, providing strong evidence for a common mechanism of catalysis in Laspo and flavoproteins of the succinate dehydrogenase/fumarate reductase family. This implies that Laspo is mechanistically distinct from other flavin-dependent amino acid oxidases, such as the prototypical D-amino acid oxidase.
Bossi
Roberto T
RT
Dipartimento di Genetica e Microbiologia, Università di Pavia, via Abbiategrasso 207, 27100 Pavia, Italy.
Negri
Armando
A
Tedeschi
Gabriella
G
Mattevi
Andrea
A
D000594:Amino Acid Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D003460:Crystallization; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D005182:Flavin-Adenine Dinucleotide / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D013379:Substrate Specificity; D013385:Succinate Dehydrogenase / Q000737:chemistry
D029968:Escherichia coli Proteins; D005182:Flavin-Adenine Dinucleotide; D013385:Succinate Dehydrogenase; D000594:Amino Acid Oxidoreductases; C031955:L-aspartate oxidase, E coli