title: Quinolinate synthetase, an iron-sulfur enzyme in NAD biosynthesis.
abstract: Nicotinamide adenine dinucleotide (NAD) plays a crucial role as a cofactor in numerous essential redox biological reactions. NAD derives from quinolinic acid which is synthesized in Escherichia coli from L-aspartate and dihydroxyacetone phosphate (DHAP) as the result of the concerted action of two enzymes, L-aspartate oxidase (NadB) and quinolinate synthetase (NadA). We report here the characterization of NadA protein from E. coli. When anaerobically purified, the isolated soluble protein contains 3-3.5 iron and 3-3.5 sulfide/polypeptide chain. Mössbauer spectra of the 57Fe-protein revealed that the majority of the iron is in the form of a (4Fe-4S)2+ cluster. An enzymatic assay for quinolinate synthetase activity was set up and allowed to demonstrate that the cluster is absolutely required for NadA activity. Exposure to air leads to degradation of the cluster and inactivate enzyme.
authors.affiliation: Laboratoire de Chimie et Biochimie des Centres Rédox Biologiques, DRDC-CB, CEA/CNRS/Université Joseph Fourier, UMR 5047, 17 Avenue des Martyrs, 38054 Grenoble Cedex 09, France. sollagnier@cea.fr
authors.forename: Sandrine
authors.initials: S
authors.lastname: Ollagnier-de Choudens
authors.forename: Laurent
authors.initials: L
authors.lastname: Loiseau
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Sanakis
authors.forename: Frédéric
authors.initials: F
authors.lastname: Barras
authors.forename: Marc
authors.initials: M
authors.lastname: Fontecave
mesh_terms: D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification; D009243:NAD / Q000096:biosynthesis*; D016415:Sequence Alignment
chemical_list: D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D009243:NAD; C022512:quinolinic acid synthetase