title: Nicotinamidase from the thermophilic archaeon Acidilobus saccharovorans: structural and functional characteristics.
abstract: Nicotinamidase is involved in the maintenance of NAD+ homeostasis and in the NAD+ salvage pathway of most prokaryotes, and it is considered as a possible drug target. The gene (ASAC_0847) encoding a hypothetical nicotinamidase has been found in the genome of the thermophilic archaeon Acidilobus saccharovorans. The product of this gene, NA_As0847, has been expressed in Escherichia coli, isolated, and characterized as a Fe(2+)-containing nicotinamidase (k(cat)/K(m) = 427 mM(-1)·sec(-1))/pyrazinamidase (k(cat)/K(m) = 331 mM(-1)·sec(-1)). NA_As0847 is a homodimer with molecular mass 46.4 kDa. The enzyme has high thermostability (T(1/2) (60°C) = 180 min, T(1/2) (80°C) = 35 min) and thermophilicity (T(opt) = 90°C, E(a) = 30.2 ± 1.0 kJ/mol) and broad pH interval of activity, with the optimum at pH 7.5. Special features of NA_As0847 are the presence of Fe2+ instead of Zn2+ in the active site of the enzyme and inhibition of the enzyme activity by Zn2+ at micromolar concentrations. Analysis of the amino acid sequence revealed a new motif of the metal-binding site (DXHXXXDXXEXXXWXXH) for homological archaeal nicotinamidases.
authors: Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow, 119071, Russia. inbi@inbi.ras.ru.
authors: T N
authors: TN
authors: Stekhanova
authors: E Y
authors: EY
authors: Bezsudnova
authors: A V
authors: AV
authors: Mardanov
authors: E M
authors: EM
authors: Osipov
authors: N V
authors: NV
authors: Ravin
authors: K G
authors: KG
authors: Skryabin
authors: V O
authors: VO
authors: Popov
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D019615:Crenarchaeota / Q000201:enzymology* / Q000235:genetics; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D020745:Genome, Archaeal; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D008969:Molecular Sequence Data; D009535:Nicotinamidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D013696:Temperature; D015032:Zinc / Q000737:chemistry / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D007477:Ions; D011994:Recombinant Proteins; D009535:Nicotinamidase; D015032:Zinc