NAD plus (NAD+, nicotinamide adenine dinucleotide) is one of the most abundant and important cofactors in living cells. Questions about NMN vs NAD often come down to a simple relationship: nicotinamide mononucleotide (NMN) is the direct precursor that cells convert into NAD+. This article explains the chemistry of both molecules, the pathways that connect them and the questions researchers have used each to investigate.
For laboratory research use only. Not for human or veterinary use. See our research use only policy.
At a glance: NAD+ identity
- Name: NAD+ (nicotinamide adenine dinucleotide, oxidised form)
- Synonyms: NAD, beta-NAD, beta-nicotinamide adenine dinucleotide, coenzyme I
- Sequence: Not applicable (dinucleotide, not a peptide)
- Molecular formula: C21H27N7O14P2
- Molecular weight: 663.4 g/mol
- CAS number: 53-84-9
- Form: Lyophilised powder
- Purity: >99% (HPLC)
- Storage: 2-8°C, dark, upright, do not freeze. Keep sealed until use.
What is NAD+?
NAD+ is a dinucleotide: two nucleotides joined through their phosphate groups. One nucleotide carries adenine and the other carries nicotinamide. The nicotinamide ring is the reactive part. It accepts a hydride ion to form NADH, and NADH donates it back to regenerate NAD+. This reversible exchange makes the NAD+/NADH couple a central electron carrier in glycolysis, the citric acid pathway and fatty acid oxidation, with NADH feeding electrons into complex I of the mitochondrial respiratory chain.
NAD+ also has a second role as a consumed substrate. Several enzyme families cleave NAD+ and release nicotinamide in the process:
- Sirtuins (SIRT1 to SIRT7), NAD+-dependent deacylases that modify histones and metabolic enzymes.
- PARPs (poly-ADP-ribose polymerases), involved in DNA damage signalling.
- CD38 and CD157, NAD+-glycohydrolases on cell surfaces and in organelles.
- SARM1, an NAD+-cleaving enzyme studied in axon degeneration.
Because these enzymes continually consume NAD+, cells must keep resynthesising it. That is where NMN comes in.
What is NMN?
Nicotinamide mononucleotide is a single nucleotide made of nicotinamide, ribose and one phosphate. Its molecular formula is C11H15N2O8P (molecular weight approximately 334.2 g/mol), roughly half the size of NAD+. NMN is not a product in our catalogue, so we include it here for comparison only.
How NMN and NAD+ are connected
The salvage pathway
In mammalian cells, most NAD+ is regenerated through the salvage pathway, which reuses the nicotinamide released by NAD+-consuming enzymes:
- Nicotinamide is converted to NMN by the enzyme nicotinamide phosphoribosyltransferase (NAMPT). This is generally regarded as the rate-limiting step.
- NMN is converted to NAD+ by NMN adenylyltransferases (NMNAT1, 2 and 3), which add the adenine nucleotide portion. The three isoforms are located in the nucleus, Golgi/cytoplasm and mitochondria respectively.
Other routes
NAD+ can also be made from tryptophan through the de novo (kynurenine) pathway, and from nicotinic acid through the Preiss-Handler pathway. Nicotinamide riboside (NR) enters the salvage route by being phosphorylated to NMN by nicotinamide riboside kinases (NRK1 and NRK2).
Methylation of nicotinamide
Not all nicotinamide is recovered. The enzyme nicotinamide N-methyltransferase (NNMT) methylates nicotinamide to 1-methylnicotinamide, removing it from the salvage pool. NNMT has become a research target in its own right, and our article on 5-Amino-1MQ, an NNMT inhibitor covers that area.
NAD+ vs NMN: key differences for researchers
- Size and charge. NAD+ is a larger, more highly charged molecule. Intact NAD+ is generally considered to cross cell membranes poorly, and extracellular NAD+ is often broken down to smaller precursors before uptake.
- Position in the pathway. NMN is one enzymatic step upstream of NAD+. Using NMN in cell models probes the NMNAT step, while adding NAD+ probes extracellular processing and uptake.
- Uptake. A 2019 study by Grozio and colleagues in Nature Metabolism proposed that Slc12a8 acts as an NMN transporter in mouse small intestine. This finding has been debated, and other groups have argued that NMN is converted to NR before entering cells.
- Analytical use. NAD+ is widely used as a reagent in enzyme assays, for example in dehydrogenase and sirtuin activity assays, where a defined, high-purity cofactor is needed.
Research context
Interest in NAD+ metabolism grew after studies reported that tissue NAD+ levels declined with age in rodent models. Imai and colleagues, including a 2011 study by Yoshino and colleagues in Cell Metabolism, investigated NMN in mouse models of diet-induced and age-associated metabolic changes. Reviews by Verdin (Science, 2015), Rajman, Chrzanowska and Sinclair (Cell Metabolism, 2018) and Covarrubias and colleagues (Nature Reviews Molecular Cell Biology, 2021) summarise this literature and its open questions. Human studies of NAD+ precursors have been small and have not established clear conclusions, and nothing in this article should be read as a claim about effects in people.
NAD+ research overlaps with other mitochondrial topics in this cluster. AMPK and sirtuin signalling feature in work on MOTS-c, the mitochondrial-derived peptide, and the integrity of the respiratory chain that oxidises NADH is the focus of SS-31 research.
Laboratory handling of NAD+
NAD+ is hygroscopic and sensitive to heat, and in solution it is more stable under mildly acidic conditions than alkaline ones, while NADH shows the opposite pattern. Store the sealed powder at 2-8°C in the dark, let the vial reach room temperature before opening and keep it closed when not in use. The oxidised and reduced forms can be distinguished spectrophotometrically, since NADH absorbs at 340 nm and NAD+ does not. For general guidance see how to store lyophilised peptides, which also applies to other lyophilised research materials.
View NAD+ in the catalogue.
Frequently asked questions
What is the difference between NAD+ and NMN?
NMN (nicotinamide mononucleotide) is a single nucleotide that cells convert into NAD+ (nicotinamide adenine dinucleotide) using NMNAT enzymes. NAD+ is the active cofactor, while NMN is its immediate precursor in the salvage pathway.
What is the difference between NAD+ and NADH?
NAD+ is the oxidised form and NADH is the reduced form carrying an extra hydride. They interconvert in redox reactions. NADH absorbs light at 340 nm, which is used to tell them apart in assays.
What is the CAS number of NAD+?
The CAS number of NAD+ is 53-84-9. Its molecular formula is C21H27N7O14P2 and its molecular weight is 663.4 g/mol.
Does Compound Cave supply NMN?
Our catalogue lists NAD+ rather than NMN. NMN is discussed in this article for comparison only.
Is NAD+ from Compound Cave suitable for consumption?
No. It is supplied for laboratory research use only and is not for human or veterinary use.
References
- Verdin E. (2015). Science, 350(6265), 1208-1213. Review of NAD+ in metabolism.
- Yoshino J, Mills KF, Yoon MJ, Imai S. (2011). Cell Metabolism, 14(4), 528-536. NMN in mouse models of diet- and age-associated metabolic change.
- Rajman L, Chrzanowska K, Sinclair DA. (2018). Cell Metabolism, 27(3), 529-547. Review of NAD+ precursor molecules.
- Grozio A, Mills KF, Yoshino J, et al. (2019). Nature Metabolism, 1(1), 47-57. Slc12a8 as a proposed NMN transporter.
- Covarrubias AJ, Perrone R, Grozio A, Verdin E. (2021). Nature Reviews Molecular Cell Biology, 22(2), 119-141. Review of NAD+ metabolism.
NAD+ and NMN occupy adjacent positions in one of the most studied pathways in cell metabolism, and understanding where each sits is the starting point for designing experiments with either.
For laboratory research use only. Not for human or veterinary use. See our research use only policy.