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Pathway Description
NAD Salvage
Escherichia coli
Metabolic Pathway
NAD molecules have a relatively short half-life. NAD can be degraded by enzymes, and the degraded NAD molecule can be recouped by NAD salvage cycles. NAD salvage cycles can be used for recycling degraded NAD products such as nicotinamide and nicotinamide D-ribonucleotide. NAD salvage cycles can also be used for absorption of exogenous NAD+. NAD reacts spontaneously with water resulting in the release of hydrogen ion, AMP and beta-nicotinamide D-ribonucleotide. This enzyme can either interact spontaneously with water resulting in the release of D-ribofuranose 5-phosphate, hydrogen ion and Nacinamide. On the other hand beta-nicotinamide D-ribonucleotide can also react with water through NMN amidohydrolase resulting in ammonium, and Nicotinate beta-D-ribonucleotide. Also it can interact with water spontaneously resulting in the release of phosphate resulting in a Nicotinamide riboside. Niacinamide interacts with water through a nicotinamidase resulting in a release of ammonium and nicotinic acid. Nicotinic acid interacts with water and phosphoribosyl pyrophosphate through an ATP driven nicotinate phosphoribosyltransferase resulting in the release of ADP, pyrophosphate and phosphate and nicotinate beta-D-ribonucleotide. Nicotinamide riboside interacts with an ATP driven NadR DNA-binding transcriptional repressor and NMN adenylyltransferase (Escherichia coli) resulting in a ADP, hydrogen ion and beta-nicotinamide D-ribonucleotide. The latter interacts with ATP and hydrogen ions through NadR DNA-binding transcriptional repressor and NMN adenylyltransferase resulting in pyrophosphate and NAD. Nicotinate beta-D-ribonucleotide is adenylated through the interaction with ATP and a hydrogen ion through a nicotinate-mononucleotide adenylyltransferase resulting in pyrophosphate and Nicotinic acid adenine dinucleotide. Nicotinic acid adenine dinucleotide interacts with L-glutamine and water through an ATP driven NAD synthease, NH3-dependent resulting in AMP, pyrophosphate, hydrogen ion, L-glutamic acid and NAD.
References
NAD Salvage References
Park UE, Roth JR, Olivera BM: Salmonella typhimurium mutants lacking NAD pyrophosphatase. J Bacteriol. 1988 Aug;170(8):3725-30.
Pubmed: 2841298
Foster JW, Baskowsky-Foster AM: Pyridine nucleotide cycle of Salmonella typhimurium: in vivo recycling of nicotinamide adenine dinucleotide. J Bacteriol. 1980 Jun;142(3):1032-5.
Pubmed: 6445894
Foster JW, Kinney DM, Moat AG: Pyridine nucleotide cycle of Salmonella typhimurium: isolation and characterization of pncA, pncB, and pncC mutants and utilization of exogenous nicotinamide adenine dinucleotide. J Bacteriol. 1979 Mar;137(3):1165-75.
Pubmed: 220211
Hillyard D, Rechsteiner M, Manlapaz-Ramos P, Imperial JS, Cruz LJ, Olivera BM: The pyridine nucleotide cycle. Studies in Escherichia coli and the human cell line D98/AH2. J Biol Chem. 1981 Aug 25;256(16):8491-7.
Pubmed: 7021549
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