What Is NAD+? Coenzyme, Not Peptide — Research Overview

NAD+ is a coenzyme, not a peptide. Nicotinamide adenine dinucleotide is built from nicotinamide, adenine, two ribose sugars and two phosphate groups. It contains no amino acids. The “NAD peptide” phrasing that circulates online is simply incorrect, though understandable: NAD+ is often sold in the same lyophilized vials and from the same catalogues as research peptides.

For laboratory research use only. The compounds discussed are not approved for human or veterinary use and are not drugs, foods or cosmetics. This article summarises published research and is not medical advice.

Key points

Dinucleotide coenzyme; C₂₁H₂₇N₇O₁₄P₂, 663.4 g/mol.
Two roles: electron carrier in redox reactions, and cosubstrate for sirtuins, CD38 and PARPs.
Reviews report an age-related decline in tissue NAD+ across model organisms.
Chemically it behaves differently from peptides: buffer and pH strongly affect its stability.
Not a peptide, so peptide-specific concerns such as aggregation do not apply.

Quick facts

Property	NAD+	NADH
Formula	C₂₁H₂₇N₇O₁₄P₂	C₂₁H₂₉N₇O₁₄P₂
Molecular weight	663.4 g/mol	665.4 g/mol
Redox state	Oxidised	Reduced
Absorbance	260 nm (adenine)	260 nm plus 340 nm
Class	Nucleotide coenzyme (not a peptide or protein)

The 340 nm absorbance of NADH is the basis of countless enzyme assays: as NAD+ is reduced to NADH, absorbance at 340 nm rises. Our NAD+ research material is supplied in 100 mg, 500 mg and 1000 mg vials.

What NAD+ does

A 2021 review in Nature Reviews Molecular Cell Biology summarises the two sides of NAD+ biology. As a redox coenzyme it is central to energy metabolism, cycling between NAD+ and NADH. As a cosubstrate it is consumed by three enzyme families: sirtuins (protein deacylases), CD38 (an NADase) and poly(ADP-ribose) polymerases (PARPs, involved in DNA repair). Through these, NAD+ influences metabolic pathways, DNA repair, chromatin remodelling, cellular senescence and immune cell function (Covarrubias et al., 2021).

Role	Enzymes	What happens to NAD+
Redox coenzyme	Dehydrogenases	Recycled (NAD+ ⇄ NADH)
Deacylation	Sirtuins	Consumed
DNA repair signalling	PARPs	Consumed
NAD+ hydrolysis	CD38	Consumed

The distinction matters: the consuming enzymes create demand that must be met by biosynthesis, which is the premise of research into NAD+ precursors.

The age-related decline literature

Reviews describe a gradual decline in tissue and cellular NAD+ with age in several model organisms, including rodents and humans, and link this to age-associated conditions (Covarrubias et al., 2021; Verdin, 2015). A 2018 review assessed the in vivo evidence for NAD-boosting molecules and the question of whether raising NAD+ improves resilience to multiple conditions rather than one (Rajman et al., 2018). These are reviews of preclinical and early clinical work; the authors themselves note how much remains unknown about NAD+ in human health.

Precursors and related molecules

Molecule	Relation to NAD+	Mass
NAD+	The coenzyme itself	663.4 g/mol
NADH	Reduced form	665.4 g/mol
NMN (nicotinamide mononucleotide)	Direct precursor	334.2 g/mol
NR (nicotinamide riboside)	Precursor, converted to NMN	—
Nicotinamide	Vitamin B3 form; salvage pathway substrate	—

Comparisons between these are covered in NMN vs NAD+ and NAD vs NAD+ vs NADH.

Handling: not like a peptide

Because NAD+ is a nucleotide, its stability profile differs from peptides, and buffer choice matters more than it typically does for a peptide solution.

Buffer: in a 43-day study at 19 °C and 25 °C, both NAD+ and NADH were most stable in Tris buffer; phosphate and HEPES gave higher degradation rates (Wolfe et al., 2024).
pH: NADH degrades faster in acid; NAD+ is less stable in alkaline conditions. An earlier factorial study ranked the main effects on NADH oxidation as pH, then temperature, then buffer, and found faster degradation in phosphate, attributed to adduct formation with the pyridine ring (Rover Júnior et al., 1998).
Temperature: even a mild increase was significant for long-term stability (Wolfe et al., 2024).
Monitoring: degradation can be followed by UV-Vis, since it proceeds through oxidation of the dihydropyridine ring.

Practical approach: prepare solutions fresh, keep them cold and protected from light, and prefer Tris over phosphate for anything stored more than briefly. See reconstituting NAD+.

Open questions

How much do circulating or supplemented NAD+ precursors actually raise NAD+ in specific human tissues?
Which of the enzyme families consuming NAD+ dominates the decline seen with age?
Does raising NAD+ reverse age-associated changes in humans, as it has in some animal models?

Related research

Frequently asked questions

Is NAD+ a peptide?

No. NAD+ (nicotinamide adenine dinucleotide) is a dinucleotide coenzyme built from nicotinamide, adenine, two riboses and two phosphates. It contains no amino acids and no peptide bonds, so it is not a peptide despite often being sold alongside research peptides.

What does NAD+ do in cells?

It carries electrons in redox reactions central to energy metabolism, and it is a cosubstrate for non-redox enzymes including sirtuins, CD38 and PARPs, which link it to DNA repair, chromatin remodelling and cellular senescence.

What is the difference between NAD and NAD+?

In practice they refer to the same molecule. The plus sign denotes the oxidised form, which carries a positive charge on the nicotinamide ring; NADH is the reduced form.

Do NAD+ levels decline with age?

Reviews report that tissue and cellular NAD+ levels decline gradually with age across multiple model organisms including rodents and humans, and this decline has been linked to several age-associated conditions.

What is NAD+'s molecular weight?

663.4 g/mol (C21H27N7O14P2) for the oxidised form; NADH is 665.4 g/mol.

References

Covarrubias AJ, et al. NAD(+) metabolism and its roles in cellular processes during ageing. Nat Rev Mol Cell Biol. 2021. PMID: 33353981 https://pubmed.ncbi.nlm.nih.gov/33353981/
Verdin E. NAD+ in aging, metabolism, and neurodegeneration. Science. 2015. PMID: 26785480 https://pubmed.ncbi.nlm.nih.gov/26785480/
Rajman L, et al. Therapeutic Potential of NAD-Boosting Molecules: The In Vivo Evidence. Cell Metab. 2018. PMID: 29514064 https://pubmed.ncbi.nlm.nih.gov/29514064/
Wolfe KD, et al. Long-Term Stability of Nicotinamide Cofactors in Common Aqueous Buffers: Implications for Cell-Free Biocatalysis. Molecules. 2024. PMID: 39598842 https://pubmed.ncbi.nlm.nih.gov/39598842/
Rover Júnior L, et al. Study of NADH stability using ultraviolet-visible spectrophotometric analysis and factorial design. Anal Biochem. 1998. PMID: 9648652 https://pubmed.ncbi.nlm.nih.gov/9648652/
PubChem Compound Summary for CID 5892, NAD. National Center for Biotechnology Information. https://pubchem.ncbi.nlm.nih.gov/compound/5892