Allosteric regulation of Bacillus subtilis NAD kinase by quinolinic acid.
NADP is essential for biosynthetic pathways, energy, and signal transduction. In living organisms, NADP biosynthesis proceeds through the phosphorylation of NAD with a reaction catalyzed by NAD kinase. We expressed, purified, and characterized Bacillus subtilis NAD kinase. This enzyme represents a new member of the inorganic polyphosphate [poly(P)]/ATP NAD kinase subfamily, as it can use poly(P), ATP, or other nucleoside triphosphates as phosphoryl donors. NAD kinase showed marked positive cooperativity for the substrates ATP and poly(P) and was inhibited by its product, NADP, suggesting that the enzyme plays a major regulatory role in NADP biosynthesis. We discovered that quinolinic acid, a central metabolite in NAD(P) biosynthesis, behaved like a strong allosteric activator for the enzyme. Therefore, we propose that NAD kinase is a key enzyme for both NADP metabolism and quinolinic acid metabolism.
Garavaglia
Silvia
S
DISCAFF-INFM, University of Piemonte Orientale Amedeo Avogadro, 28100 Novara, Italy.
Galizzi
Alessandro
A
Rizzi
Menico
M
D000494:Allosteric Regulation; D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009249:NADP / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D017378:Quinolinic Acid / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013696:Temperature; D014158:Transcription, Genetic
D011994:Recombinant Proteins; D009249:NADP; D017853:Phosphotransferases (Alcohol Group Acceptor); C021844:NAD kinase; D017378:Quinolinic Acid