Nicotinamidase from the thermophilic archaeon Acidilobus saccharovorans: Structural and functional characteristics

作者：Stekhanova T N^*; Bezsudnova E Y; Mardanov A V; Osipov E M; Ravin N V; Skryabin K G; Popov V O

来源：Biochemistry-Moscow, 2014, 79(1): 54-61.

DOI：10.1134/S0006297914010088

• nicotinamidase
• pyrazinamidase
• archaeon
• C-D-K catalytic triad
• metal binding motif

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 Fe2+-containing nicotinamidase (k (cat)/K (m) = 427 mM(-1)center dot sec(-1))/pyrazinamidase (k (cat)/K (m) = 331 mM(-1)center dot sec(-1)). NA_As0847 is a homodimer with molecular mass 46.4 kDa. The enzyme has high thermostability (T-1/2 (60A degrees C) = 180 min, T-1/2 (80A degrees C) = 35 min) and thermophilicity (T-opt = 90A degrees 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_As084 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.

• 出版日期2014-1