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What Is NAD+?

NAD+ (nicotinamide adenine dinucleotide, CAS 53-84-9, MW 663.43 g/mol) is a pyridine nucleotide coenzyme found in all living cells. It functions as a hydride-transfer agent in hundreds of oxidation-reduction reactions central to energy metabolism and additionally serves as a substrate for signaling enzymes including sirtuins, PARPs, and CD38. NAD+ exists in two interconvertible forms — the oxidized NAD+ and reduced NADH — and its intracellular ratio is a key indicator of cellular redox state. Research has examined NAD+ biology in the context of metabolic regulation, DNA repair, circadian rhythm coordination, and aging. This profile covers molecular identity, proposed research mechanisms, and peer-reviewed references.

Chemical Properties

Property	Value
CAS Number	53-84-9
Molecular Formula	C₂₁H₂₇N₇O₁₄P₂
Molecular Weight	663.43 g/mol
PubChem CID	5892
IUPAC Name	[(2R,3S,4R,5R)-5-(3-carbamoylpyridin-1-ium-1-yl)-3,4-dihydroxyoxolan-2-yl]methyl (2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl phosphate
Classification	Pyridine nucleotide coenzyme
Redox Pair	NAD+ / NADH
Biological Role	Hydride carrier; sirtuin substrate; PARP substrate

Historical Development and Discovery

NAD+ was first identified in 1906 by Arthur Harden and William John Young, who discovered a heat-stable factor in yeast extracts required for fermentation. The complete structure was elucidated by Otto Heinrich Warburg in the 1930s, and Warburg’s characterization of its role in hydrogen transfer earned him the Nobel Prize in Physiology or Medicine in 1931. Subsequent decades established NAD+ as a central coenzyme in cellular respiration — functioning in glycolysis, the citric acid cycle, and the electron transport chain. A major expansion in NAD+ biology began in the 1960s with Chambon’s discovery that NAD+ is a substrate for poly-ADP-ribose polymerases (PARPs), and again in the early 2000s when Guarente and colleagues demonstrated that sirtuins — NAD+-dependent deacetylases — regulate lifespan in model organisms. These findings repositioned NAD+ from a metabolic cofactor to a central regulator of cellular signaling and aging biology.

Chemical Architecture and Structural Features

Property	Detail
Components	Nicotinamide mononucleotide (NMN) + adenosine monophosphate (AMP) linked by pyrophosphate bond
Nicotinamide moiety	Pyridine ring bearing carboxamide group; site of hydride transfer
Adenine moiety	Purine base linked to ribose-5-phosphate
Charge at pH 7	Net negative (phosphate groups)
Absorption maximum	260 nm (adenine); 340 nm (NADH, reduced form)
Stability	Susceptible to hydrolysis at acidic pH; more stable at neutral-alkaline pH

Research Mechanisms

• Redox coenzyme activity: NAD+ accepts hydride (H⁻) from metabolic substrates in glycolysis, beta-oxidation, and the citric acid cycle, becoming NADH. NADH then donates electrons to Complex I of the mitochondrial electron transport chain, driving ATP synthesis. The NAD+/NADH ratio is extensively studied as an indicator of metabolic state.
• Sirtuin activation: Sirtuins (SIRT1–7) are NAD+-dependent protein deacetylases and ADP-ribosyltransferases. Published research has established that sirtuin activity requires NAD+ as a co-substrate, with NAD+ consumed stoichiometrically in each deacetylation reaction. Sirtuin targets studied in the context of NAD+ availability include PGC-1α, FOXO transcription factors, p53, and histones.
• PARP substrate: Poly-ADP-ribose polymerases (PARPs) use NAD+ to add poly-ADP-ribose chains to target proteins in response to DNA strand breaks. PARP-mediated NAD+ consumption is a major pathway of NAD+ depletion under genotoxic stress, and the interaction between PARP activity, NAD+ levels, and DNA repair has been extensively studied.
• CD38 and cyclic ADP-ribose signaling: CD38 is an NAD+-consuming ectoenzyme that produces cyclic ADP-ribose (cADPR) and ADPR, second messengers involved in calcium mobilization. CD38 activity has been identified as a significant contributor to age-related NAD+ decline in published research.
• Circadian rhythm coordination: Research has established bidirectional links between NAD+ metabolism and the circadian clock. NAMPT — the rate-limiting enzyme in the NAD+ salvage pathway — is rhythmically expressed, and SIRT1 has been shown to deacetylate core clock components including CLOCK and BMAL1 in an NAD+-dependent manner.
• Declining NAD+ with age: A substantial body of preclinical and human literature has documented declining intracellular and circulating NAD+ levels with age across multiple tissues, including skeletal muscle, liver, brain, and adipose tissue. Research has examined whether NAD+ precursor supplementation (NMN, NR) restores tissue NAD+ levels in animal models and human cohorts.

Research Areas

Metabolic Biology

NAD+ is fundamental to cellular energy metabolism. Decades of biochemical research have characterized its role as a hydride carrier in glycolysis, fatty acid oxidation, the citric acid cycle, and mitochondrial respiratory chain function. The NAD+/NADH ratio is studied as a reporter of cellular metabolic state, and research has examined how manipulating NAD+ availability affects mitochondrial biogenesis, fatty acid oxidation capacity, and ATP production in diverse cell and tissue models.

Sirtuin Biology & Aging Research

The discovery of sirtuins as NAD+-dependent enzymes transformed NAD+ from a metabolic intermediate into a subject of aging biology research. Published studies have investigated how declining NAD+ availability with age affects sirtuin activity, mitochondrial function, and metabolic gene expression. Research has also examined whether restoring NAD+ levels in aged animal models rescues sirtuin-dependent physiological endpoints.

DNA Repair Research

PARP enzymes consume NAD+ at sites of DNA damage, connecting DNA repair efficiency to cellular NAD+ levels. Research has examined the relationship between NAD+ availability, PARP activity, and DNA repair capacity, as well as the consequences of NAD+ depletion following genotoxic stress. This area has also intersected with cancer biology research examining PARP inhibitor mechanisms.

Neuroscience Research

NAD+ has been investigated in neuroscience contexts including neuronal energy metabolism, axonal integrity, and neurodegeneration models. Published research has examined the role of NAD+ in SIRT1-mediated neuronal survival signaling, and studies using WLDS (slow Wallerian degeneration) mice — which overexpress NMNAT, an NAD+ biosynthetic enzyme — have provided evidence linking NAD+ synthesis to axonal protection in preclinical models.

Frequently Asked Questions

What is the CAS number for NAD+?

The CAS number for NAD+ (nicotinamide adenine dinucleotide, oxidized form) is 53-84-9. Its PubChem CID is 5892, molecular formula is C₂₁H₂₇N₇O₁₄P₂, and molecular weight is 663.43 g/mol.

What is the difference between NAD+ and NADH?

NAD+ and NADH are the two interconvertible redox forms of nicotinamide adenine dinucleotide. NAD+ is the oxidized form — it accepts a hydride ion (H⁻) from metabolic substrates during catabolic reactions, becoming NADH (the reduced form). NADH then donates electrons to the mitochondrial electron transport chain. The ratio of NAD+ to NADH in a cell reflects its metabolic and redox state. Enzymatic assays that detect NADH at 340 nm absorption are used to measure NAD+/NADH ratios in research settings.

Why do sirtuins require NAD+?

Sirtuins (SIRT1–7) are NAD+-dependent deacylases — they use NAD+ as a co-substrate rather than a cofactor. In each catalytic cycle, one molecule of NAD+ is consumed and cleaved, releasing nicotinamide and producing O-acetyl-ADP-ribose alongside the deacetylated substrate. This stoichiometric requirement means sirtuin activity is directly coupled to intracellular NAD+ availability, which is why declining NAD+ levels with age are studied in the context of sirtuin function.

What enzymes consume NAD+ in cells?

Beyond its role as a redox carrier, NAD+ is consumed as a substrate by three main enzyme families: sirtuins (deacetylases, SIRT1–7), PARPs (poly-ADP-ribose polymerases, involved in DNA repair), and CD38/CD157 (ectoenzymes producing calcium-signaling second messengers cADPR and ADPR). PARP activation during DNA damage can cause rapid, large-scale NAD+ depletion in stressed cells.

How is NAD+ synthesized in cells?

Cells maintain NAD+ levels through two main routes. The de novo pathway synthesizes NAD+ from tryptophan via the kynurenine pathway, producing quinolinic acid and ultimately nicotinic acid mononucleotide (NaMN). The salvage pathway recycles nicotinamide (NAM) — produced when NAD+ is consumed by sirtuins, PARPs, or CD38 — back to NAD+ via the rate-limiting enzyme NAMPT (nicotinamide phosphoribosyltransferase). Precursors NMN and NR feed into the salvage pathway upstream of or at NMNAT enzymes.

Does NAD+ decline with age?

Yes. Published research across multiple tissues and species has documented that NAD+ levels decline with age. Studies in rodents and human subjects have reported declining NAD+ in skeletal muscle, liver, brain, and adipose tissue with increasing age. Proposed mechanisms include increased CD38 expression with age, reduced NAMPT activity, and accumulated DNA damage driving chronic PARP activation. This age-related decline has motivated substantial research into NAD+ precursor supplementation as a tool in aging biology.

What is NAMPT and why is it important in NAD+ research?

NAMPT (nicotinamide phosphoribosyltransferase) is the rate-limiting enzyme in the NAD+ salvage pathway. It converts nicotinamide (NAM) to nicotinamide mononucleotide (NMN), the penultimate step before NMNAT enzymes complete NAD+ synthesis. NAMPT expression is rhythmically regulated by the circadian clock and is inhibited by its own product nicotinamide. In research contexts, NAMPT activity is studied as a determinant of intracellular NAD+ availability, and NAMPT inhibitors are used as tools to model NAD+ depletion.

What is the molecular weight of NAD+?

The molecular weight of NAD+ (free acid form) is 663.43 g/mol, with molecular formula C₂₁H₂₇N₇O₁₄P₂. The disodium salt form (NAD+ · 2Na), commonly used in research-grade preparations, has a molecular weight of 709.41 g/mol.

Published Research

• Imai S, Guarente L. “NAD+ and sirtuins in aging and disease.” Trends in Cell Biology. 2014;24(8):464-471. PMID: 24786309.
• Verdin E. “NAD+ in aging, metabolism, and neurodegeneration.” Science. 2015;350(6265):1208-1213. PMID: 26785480.
• Yoshino J, et al. “NAD+ intermediates: The biology and therapeutic potential of NMN and NR.” Cell Metabolism. 2018;27(3):513-528. PMID: 29249689.
• Cantó C, et al. “The NAD+ precursor nicotinamide riboside enhances oxidative metabolism and protects against high-fat diet-induced obesity.” Cell Metabolism. 2012;15(6):838-847. PMID: 22682224.
• Bonkowski MS, Sinclair DA. “Slowing ageing by design: the rise of NAD+ and sirtuin-activating compounds.” Nature Reviews Molecular Cell Biology. 2016;17(11):679-690. PMID: 27552971.
• Chini CCS, et al. “The dysregulation of NAD+ metabolism with age leads to a catastrophic energy crisis in ageing.” Cell Metabolism. 2022;34(3):345-355. PMID: 35263593.

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Intended Use: NAD+ supplied by ITide Laboratories is intended for laboratory research purposes by qualified professionals only. Not for human, animal, diagnostic, or therapeutic use. This compound has not been evaluated by the FDA for clinical application, is not manufactured to pharmaceutical standards, and all applicable local, state, and federal regulations governing research compounds apply.

Research Use Only Disclaimer

NAD+ (CAS 53-84-9) is intended for laboratory research purposes by qualified professionals only. Not for human, animal, diagnostic, or therapeutic use. This compound has not been evaluated by the FDA for clinical application, is not manufactured to pharmaceutical standards, and all applicable local, state, and federal regulations governing research compounds apply.