No. It is a dinucleotide coenzyme built from nucleotide chemistry — no amino acids, no peptide bonds.

Two things: carries electrons in metabolism by cycling to NADH, and acts as a consumed substrate for sirtuins, PARPs and CD38.

Why do studies use NR and NMN instead?

NAD+ is too large and too charged to cross plasma membranes. Its smaller precursors do, so cells can build NAD+ from them internally.

NAD+

What Is NAD+? A Complete Research Overview

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-234 cited sources

NAD+ is nicotinamide adenine dinucleotide, a coenzyme present in every living cell at 663.4 Da. It is not a peptide — it contains no amino acids and no peptide bonds. It carries electrons in metabolic reactions and serves as a consumed substrate for several classes of enzyme.

Key facts

Full name: Nicotinamide adenine dinucleotide
Molecular weight: 663.4 Da
Formula: C21H27N7O14P2
PubChem CID: 5892
Chemical class: Dinucleotide coenzyme
Peptide?: No — no amino acids, no peptide bonds
Present in: Every living cell

What it actually is

Two nucleotides joined tail to tail through a pyrophosphate bridge. One carries nicotinamide, the other adenine. That construction — sugar, base, phosphate, twice over — is nucleotide chemistry, the same chemistry that builds DNA and RNA. It has nothing structurally in common with a peptide.

The two jobs it does

First, electron carrier. NAD+ accepts a hydride to become NADH and passes it on, cycling between the two forms continuously without being consumed. This is the role in glycolysis and the citric acid cycle. Second, and quite differently, NAD+ is a substrate that gets used up — sirtuins, PARPs and CD38 all cleave it. That second role is why cellular levels can fall at all.

Research material referenced

NAD+ 500mg — third-party HPLC tested

View — £49.99

Why the second role is the interesting one

A pure electron carrier would recycle indefinitely and its concentration would be a housekeeping detail. Because sirtuins and PARPs consume NAD+ as a substrate, demand from those enzymes draws down the pool, and the pool has to be resynthesised. That consumption is what connects NAD+ to DNA repair, to stress responses, and to the ageing literature that has grown up around it.

Why the field works with precursors

NAD+ is large and carries two negatively charged phosphate groups, which means it does not cross plasma membranes. Cells make their own from smaller precursors that do get in — nicotinamide riboside at 255.25 Da and nicotinamide mononucleotide at 334.22 Da. Essentially all of the human trial literature uses those precursors rather than NAD+ itself, and that is a considered choice rather than an accident of availability.

What this means for a peptide catalogue

General peptide guidance does not apply here. There is no sequence, no purity-by-amino-acid-analysis, no disulfide chemistry, no protease susceptibility. The relevant chemistry is nucleotide chemistry — glycosidic and pyrophosphate bond hydrolysis — and the relevant literature is metabolic rather than peptide pharmacology.

Regulatory position

NAD+ holds no marketing authorisation as a medicine from the MHRA, EMA or FDA. Material supplied here is for laboratory research only, and no claim is made about ageing, energy or any condition in any person.

Extended research context

The NAD+ deep dive

Deep dive: the compound in this catalogue that is not a peptide

NAD+ contains no amino acids and no peptide bonds. It is a dinucleotide - a nicotinamide nucleotide and an adenine nucleotide joined through a pyrophosphate bridge - which is the structural grammar of ATP and of RNA, not of a protein. It sits in a peptide catalogue because it reaches the same buyers, not because it belongs there. Saying so matters practically rather than pedantically: essentially all of the general handling guidance on this site is written for peptides and is the wrong guidance here. There is no sequence to verify, so purity by amino acid analysis is meaningless. There are no deletion sequences, because there is no stepwise coupling to produce them. Net peptide content, the figure that decides how much material a lyophilised peptide vial actually contains, has no analogue at all. Even the instruction that does carry over - dry, cold, dark - protects different chemistry, guarding glycosidic and pyrophosphate bonds rather than peptide bonds and methionine residues.

Deep dive: why the finished molecule is the least deliverable of the three

NAD+ carries two negatively charged phosphates and weighs 663.4 Da, and neither property is compatible with crossing a lipid bilayer. Extracellular NAD+ is also actively consumed: CD38 is an ectoenzyme with its active site facing outward, and Covarrubias and colleagues reported in Nature Metabolism in 2020 that senescent cells drive tissue NAD+ decline specifically by raising CD38 activity. Put those together and administered NAD+ is a molecule that cannot get in and is being degraded while it waits. Whatever follows most plausibly runs through its breakdown to smaller nicotinamide-containing species, which cells then take up and rebuild NAD+ from internally - which is to say, through exactly the precursors people otherwise take directly. This is why every substantial randomised trial in the field used nicotinamide riboside at 255.25 Da or nicotinamide mononucleotide at 334.22 Da rather than the coenzyme itself. The naming inverts the pharmacology: the finished molecule sounds like the most direct option and is the least.

Deep dive: good early evidence, and the gap that keeps getting closed rhetorically

The randomised human literature here is better than for most of this catalogue. NADPARK was a randomised phase I trial of nicotinamide riboside in Parkinson disease in Cell Metabolism. Orr and colleagues ran a randomised placebo-controlled study in older adults in GeroScience. Yoshino and colleagues published NMN and muscle insulin sensitivity in Science. These are real trials in real journals. What they measured, largely, is whether the intervention does what it is supposed to biologically - and raising a biomarker is not the same as changing an outcome. The step that gets taken rhetorically is from a decline that is real, through a mechanism that is identified, to a benefit that has not been demonstrated. Each link looks small; the chain is not. Nothing in this field approaches the scale of what settled the incretin questions, where TRIUMPH alone enrolled more than 5,800 participants with hard clinical endpoints.

Research applications

▸Cellular NAD+ metabolism and salvage pathway research
▸Sirtuin, PARP and CD38 enzyme activity studies
▸Redox biochemistry and NAD+/NADH ratio measurement
▸Cellular senescence and ageing biology research
▸Mitochondrial function and metabolic assay work
▸Comparative precursor uptake and conversion studies

Handling checklist

✓Verify against CID 5892, 663.4 Da, C21H27N7O14P2 - not by sequence
✓Do not apply peptide purity or net peptide content logic - neither exists here
✓Store lyophilised, cold, dry and protected from light
✓Prepare solutions fresh; nucleotide bonds hydrolyse readily in water
✓Be aware NAD+ and NADH are separately quantifiable oxidation states
✓Identity is confirmed by mass and chromatography against a reference standard

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Applying peptide handling and purity guidance to NAD+

Fix: It is a dinucleotide with no peptide bonds. Sequence verification, protease concerns, disulfide chemistry and net peptide content are all inapplicable.

✗ Assuming administered NAD+ enters cells intact

Fix: Two negative phosphate charges and 663 Da prevent membrane crossing, and CD38 degrades it extracellularly. Effects most plausibly run through breakdown products.

✗ Reading precursor trial results as evidence for NAD+ itself

Fix: Every substantial randomised trial used NR or NMN. NAD+ has essentially no comparable human literature.

✗ Treating a biomarker increase as a demonstrated benefit

Fix: Raising NAD+-related markers is reasonably supported. Durable clinical outcome data does not exist.

✗ Taking a precursor's food supplement status as evidence of efficacy

Fix: Supplement frameworks assess safety for consumption, not efficacy, and permit no therapeutic claims.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

Is NAD+ a peptide?: No. It is a dinucleotide coenzyme built from nucleotide chemistry — no amino acids, no peptide bonds.
What does NAD+ do?: Two things: carries electrons in metabolism by cycling to NADH, and acts as a consumed substrate for sirtuins, PARPs and CD38.
Why do studies use NR and NMN instead?: NAD+ is too large and too charged to cross plasma membranes. Its smaller precursors do, so cells can build NAD+ from them internally.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

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