NAD+, 5-amino-1MQ and glutathione: which are peptides?

Three catalog staples that share a shelf with peptides. Only one is a peptide. What each molecule actually is, from PubChem, and why the distinction changes what a certificate should show.

By Touchstone PeptidesSeptember 22, 20266 minute read

Of the three, only glutathione is a peptide. NAD+ is a dinucleotide with no amino acids in it, and 5-amino-1MQ is a small aromatic cation, a substituted quinolinium, with no peptide bond. Glutathione is a genuine tripeptide of glutamate, cysteine and glycine, though one of its two bonds is not a normal backbone peptide bond. All three sit on peptide shelves for commercial reasons, not chemical ones.

What makes something a peptide

The IUPAC-IUB definition is short: "A peptide is any compound produced by amide formation between a carboxyl group of one amino acid and an amino group of another." That gives two tests: the molecule must be made of amino acids, and they must be joined by amide (peptide) bonds. The catalog's own explainer, What a peptide is, draws the same line.

NAD+ is a dinucleotide

PubChem's record for NAD (CID 5892, listed under the name nadide) carries two descriptions worth quoting. DrugBank's: "A coenzyme composed of ribosylnicotinamide 5'-diphosphate coupled to adenosine 5'-phosphate by pyrophosphate linkage." The NCI Thesaurus's: "Nadide is a dinucleotide of adenine and nicotinamide."

So the parts are a nicotinamide ring, an adenine ring, two ribose sugars and a pyrophosphate bridge. There is no amino acid anywhere in the structure and no amide bond joining two amino acids. The formula is C21H27N7O14P2, average molecular weight 663.4, CAS 53-84-9. The "+" in NAD+ marks the positive charge on the nicotinamide nitrogen in the oxidized form; NADH is the reduced form.

NAD+ is a nucleotide-class coenzyme, not a peptide, and it is not made by solid-phase peptide synthesis. That matters for the certificate: an HPLC purity figure for NAD+ is a small-molecule assay, and "net peptide content" is not a meaningful field for it. We file it under research compounds, as NAD+ in a lyophilized vial and as an NAD+ liquid spray, an aqueous solution.

Status as of September 21, 2026. NAD+ is not a component of any FDA-approved drug. It appears on FDA's 503A Category 1 list (updated May 14, 2026) as "Nicotinamide Adenine Dinucleotide (NAD)," alongside the reduced form NADH; a disodium salt trihydrate form is listed separately in 503A Category 3. Category 1 means FDA has said it does not intend to act against a compounder using the substance under the conditions of its interim policy; it is not an approval. NAD+ is not named in WADA's 2026 Prohibited List.

5-Amino-1MQ is a quinolinium small molecule

5-Amino-1MQ is 5-amino-1-methylquinolinium: a quinoline ring system (a benzene fused to a pyridine) carrying a methyl group on the ring nitrogen, which gives the nitrogen a permanent positive charge, and an amino group at position 5. PubChem (CID 950107) gives the formula as C10H11N2+, molecular weight 159.21, CAS 685079-15-6. It is a cation, so the solid in a vial is a salt, and the certificate should name the counter-ion.

There are no amino acids and no amide bonds. It fails both tests, and at 159 daltons it is smaller than a single tryptophan residue's contribution to a chain.

In the literature it is described as an inhibitor of nicotinamide N-methyltransferase (NNMT), the enzyme that methylates nicotinamide. A 2018 paper in Biochemical Pharmacology characterised a series of "methylquinolinium scaffolds with primary amine substitutions" as membrane-permeable, selective NNMT inhibitors and studied one of them in a mouse model; a 2021 bioanalytical paper calls 5-amino-1-methyl quinolinium "a potent Nicotinamide N-methyl transferase (NNMT) inhibitor." This site makes no claim about what follows from that mechanism in a person.

Status, same date. 5-Amino-1MQ has no US approval, no ClinicalTrials.gov record, and does not appear on any FDA 503A or 503B category list. That is a status by absence. It is not named in WADA's 2026 Prohibited List.

5-Amino-1MQ sits on the same research compounds shelf.

Glutathione is a tripeptide, with a twist

Glutathione passes both tests. PubChem's record (CID 124886) describes it as "a tripeptide compound consisting of glutamic acid attached via its side chain to the N-terminus of cysteinylglycine." Three amino acids, two amide bonds, formula C10H17N3O6S, molecular weight 307.33, CAS 70-18-8.

The twist is in the phrase "via its side chain." In an ordinary peptide the bond runs from the alpha-carboxyl of one residue to the alpha-amine of the next. In glutathione the glutamate is joined through its side-chain gamma-carboxyl instead, which is why the systematic name is gamma-glutamylcysteinylglycine and why the sequence is often written γ-Glu-Cys-Gly rather than ECG. The IUPAC-IUB recommendations use exactly this molecule as their worked example of a peptide bond that does not follow the backbone. The cysteine-glycine bond is a normal one.

The gamma linkage has practical consequences. Standard solid-phase synthesis makes alpha bonds by default, so glutathione is not made the way the rest of the shelf is made. Its free thiol on cysteine is the reactive group that gives the molecule its chemistry in cells, and it is also the group that oxidises in the vial.

Our glutathione is a lyophilized vial. We have not yet verified a US regulatory status line for it against primary sources, so none is published here.

The three side by side

	NAD+	5-Amino-1MQ	Glutathione
Class	dinucleotide coenzyme	quinolinium cation, small molecule	tripeptide
Amino acids	none	none	Glu, Cys, Gly
Peptide bonds	none	none	two (one gamma-linked)
Formula	C21H27N7O14P2	C10H11N2+	C10H17N3O6S
Molecular weight	663.4	159.21	307.33
CAS	53-84-9	685079-15-6	70-18-8
PubChem CID	5892	950107	124886
Made by SPPS	no	no	not by the default route
Net peptide content on a COA	not applicable	not applicable	applicable

Why they sit on peptide shelves

The research-reagent market grew up around lyophilized vials, and buyers who order one lyophilized vial tend to order the next from the same catalog. NAD+ and 5-amino-1MQ arrived on peptide shelves because the customers were already there, not because anyone classified them. Most catalogs still file both under "peptides."

We file them under research compounds because the category tells you what to expect on the certificate. For a peptide the certificate should carry HPLC purity, mass-spectrometry identity and net peptide content. For NAD+ or 5-amino-1MQ the identity check is a small-molecule mass and the "peptide content" line has no meaning; a certificate that prints one anyway is a sign the lab used a peptide template without reading the product name. What is on our certificates is described at purity and methods.

Sources

For laboratory research use only. Not a drug, not a supplement, and nothing here is a claim about what any of this material does in a person or an animal.

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