Nicotinamide adenine dinucleotide (NAD+) is synthesized via two major pathways in prokaryotic and eukaryotic systems: the de novo biosynthesis pathway from tryptophan precursors, or the salvage biosynthesis pathway from either extracellular nicotinic acid or various intracellular NAD+ decomposition products. NAD+ biosynthesis via the salvage pathway has been linked to an increase in yeast replicative lifespan under calorie restriction (CR). However, the relative contribution of each pathway to NAD+ biosynthesis under both normal and CR conditions is not known. Here, we have performed lifespan, NAD+ and NADH (the reduced form of NAD+) analyses on BY4742 wild-type, NAD+ salvage pathway knockout (npt1Delta) and NAD+ de novo pathway knockout (qpt1Delta) yeast strains cultured in media containing either 2% glucose (normal growth) or 0.5% glucose (CR). We have utilized 14C labelled nicotinic acid in the culture media combined with HPLC speciation and both UV and 14C detection to quantitate the total amounts of NAD+ and NADH and the amounts derived from the salvage pathway. We observed that wild-type and qpt1Delta yeast exclusively utilized extracellular nicotinic acid for NAD+ and NADH biosynthesis under both the 2% and 0.5% glucose growth conditions, suggesting that the de novo pathway plays little role if a functional salvage pathway is present. We also observed that NAD+ concentrations decreased in all three strains under CR. However, unlike the wild-type strain, NADH concentrations did not decrease and NAD+: NADH ratios did not increase under CR for either knockout strain. Lifespan analyses revealed that CR resulted in a lifespan increase of approximately 25% for the wild-type and qpt1Delta strains, while no increase in lifespan was observed for the npt1Delta strain. In combination, these data suggest that having a functional salvage pathway is required for lifespan extension under CR.
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Evidence ID | Analyze ID | Gene/Complex | Systematic Name/Complex Accession | Qualifier | Gene Ontology Term ID | Gene Ontology Term | Aspect | Annotation Extension | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Phenotype | Experiment Type | Experiment Type Category | Mutant Information | Strain Background | Chemical | Details | Reference |
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Evidence ID | Analyze ID | Gene | Gene Systematic Name | Disease Ontology Term | Disease Ontology Term ID | Qualifier | Evidence | Method | Source | Assigned On | Reference |
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Evidence ID | Analyze ID | Regulator | Regulator Systematic Name | Target | Target Systematic Name | Direction | Regulation of | Happens During | Regulator Type | Direction | Regulation Of | Happens During | Method | Evidence | Strain Background | Reference |
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Site | Modification | Modifier | Source | Reference |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Allele | Assay | Annotation | Action | Phenotype | SGA score | P-value | Source | Reference | Note |
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Evidence ID | Analyze ID | Interactor | Interactor Systematic Name | Interactor | Interactor Systematic Name | Assay | Annotation | Action | Modification | Source | Reference | Note |
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Complement ID | Locus ID | Gene | Species | Gene ID | Strain background | Direction | Details | Source | Reference |
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Evidence ID | Analyze ID | Dataset | Description | Keywords | Number of Conditions | Reference |
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