5-Amino-1MQ: Structure, NNMT Enzyme Assays and Analysis

5-Amino-1MQ (5-amino-1-methylquinolinium) is a small molecule, not a peptide: a quinoline ring that carries a methyl group on its ring nitrogen and an amino group at position 5, giving a permanently charged cation of about 159.2 g/mol (formula C10H11N2+). Because it is a cation, it exists as a salt, most often the iodide (about 286.1 g/mol). It comes from a 2017 structure-activity series of N-methylated quinolinium compounds from the University of Texas Medical Branch, in which quinoliniums inhibited the enzyme nicotinamide N-methyltransferase (NNMT) in cell-free assays with IC50 values around 1 µM [1].

5-Amino-1MQ at a glance

Source: PubChem compound records 950107 and 66522933 (quoted, not linked); references 1 and 7. Masses calculated from atomic composition.

Research materials: Vortex supplies 5-Amino-1MQ as a dry research reagent in a sealed vial: 5-Amino-1MQ 50mg. Lab reports: /coa/.

What 5-Amino-1MQ is: a quinolinium, not a peptide

5-Amino-1MQ is often sold alongside peptides and called one. It is not. A peptide is a chain of amino acid residues joined by amide bonds. 5-Amino-1MQ has no amide bond and no residues. It is a fused bicyclic aromatic ring system with two small substituents.

The parent ring is quinoline: a benzene ring fused to a pyridine ring, with the nitrogen at position 1. Positions 2 to 4 sit on the nitrogen-containing ring, and positions 5 to 8 sit on the carbocyclic ring. 5-Amino-1MQ has two changes to that skeleton:

• N-methylation at position 1. Adding a methyl group to the ring nitrogen gives that nitrogen four bonds and a permanent positive charge. The result is a quaternary quinolinium ion. Unlike an amine that is charged only at low pH, a quaternary nitrogen stays charged at every pH.
• An amino group at position 5. This is an aromatic amine on the carbocyclic ring. It is conjugated with the electron-poor quinolinium ring, which makes the molecule a strong ultraviolet absorber and gives it its own chemistry, separate from the charged nitrogen.

“1MQ” stands for 1-methylquinolinium, the core shared by the whole 2017 compound series [1].

Salt forms of 5-Amino-1MQ

A permanent cation cannot exist as a neutral solid on its own. It needs a negatively charged counter-ion, and the counter-ion becomes part of the material’s formula, mass and CAS number. That is why 5-Amino-1MQ has two CAS numbers: one for the cation (685079-15-6) and one for the iodide salt (42464-96-0).

Quaternary N-methyl heterocycles are commonly made by alkylating the ring nitrogen with a methylating agent such as iodomethane, a quaternisation reaction that delivers the iodide salt directly. Other counter-ions, such as chloride, can be introduced by ion exchange. Each one changes the arithmetic:

Source: calculated from standard atomic masses. The chloride row is a worked comparison, not a statement about any supplied material.

The practical consequence is in net content. 50 mg of the iodide salt contains about 27.8 mg of the 5-amino-1-methylquinolinium cation. A label or report that gives a mass should say which form it refers to. Iodide salts can slowly oxidise in air and light to iodine, which is yellow-brown, so a colour change in an iodide salt can come from the counter-ion rather than from the organic cation.

NNMT: the methyltransferase behind the 5-Amino-1MQ literature

Nicotinamide N-methyltransferase (NNMT) is a cytosolic enzyme that moves a methyl group from the cofactor S-adenosyl-L-methionine (SAM) onto the ring nitrogen of nicotinamide and other pyridine-type compounds [1, 2]. The products are 1-methylnicotinamide (MNA) and S-adenosyl-L-homocysteine (SAH). The reaction is a methyl transfer to an aromatic nitrogen, which is exactly the bond that defines a quaternary pyridinium or quinolinium ion.

The active site

Peng and colleagues solved the crystal structure of human NNMT as a ternary complex with SAH and nicotinamide at 2.7 Å resolution [3]. Mutating two active-site residues, D197 (near the nicotinamide amide group) and Y20 (whose hydroxyl contacts both the nicotinamide ring and SAH), lowered kcat/Km by two to three orders of magnitude [3].

Crystal structures of monkey and mouse NNMT bound to the end product, MNA, and to SAH were reported in 2017 at 2.30 Å and 1.88 Å [4]. The fold matches human NNMT. MNA sat in the active site and appeared trapped there by a bridge between a long helix and a long C-terminal loop, which the authors proposed as the structural basis for MNA acting as a feedback inhibitor of the enzyme [4]. That observation matters for 5-Amino-1MQ: a methylated, positively charged aromatic ring is the kind of molecule the active site holds onto.

The reaction order

Two kinetic studies reached different models. Using a fluorescence assay, Neelakantan and colleagues fitted their steady-state data best with a random bireactant mechanism, in which either substrate can bind the free enzyme but both bind about 20-fold more tightly to the complementary binary complex [5]. Loring and Thompson, using initial-velocity, product-inhibition and dead-end inhibitor studies, concluded that NNMT follows a rapid-equilibrium ordered mechanism: SAM binds first, then nicotinamide, and after methyl transfer the methylated product and SAH leave in turn [6]. Which model holds may depend on the assay conditions.

Cell-free NNMT assays and the 5-Amino-1MQ series

A fluorescent product: 1-methylquinolinium

Most methyltransferase assays measure a product indirectly, through coupled enzymes. In 2017 the Texas group described a direct, non-coupled assay for NNMT [5]. Its substrate was quinoline. NNMT methylates the quinoline nitrogen to form 1-methylquinolinium, which fluoresces, so product formation can be followed in real time with a fluorescence reader [5]. The authors used the assay to generate concentration-response curves for known NNMT inhibitors and proposed it for screening chemical libraries [5]. That product, 1-methylquinolinium, is the core of 5-Amino-1MQ.

The 2017 structure-activity study

The same group then screened N-methylated quinolinium, isoquinolinium, pyridinium and benzimidazolium or benzothiazolium analogues against NNMT [1]. The inhibitors they found spanned more than a 1,000-fold range of activity. Quinoliniums stood out as the most promising scaffold, with IC50 values in the low micromolar range, around 1 µM [1].

The authors also docked the compounds computationally into the nicotinamide-binding site of NNMT. Docking scores correlated with the measured IC50 values, and the predicted binding poses placed the quinoliniums in the substrate site rather than the SAM site [1]. In other words, the series was modelled as competing with nicotinamide for the acceptor pocket.

Source: abstracts of references 1 and 3 to 6, checked on PubMed. All are cell-free enzyme, structural or computational studies.

What the 5-Amino-1MQ literature looks like

The record is small. A PubMed search on 21 October 2026 for “5-amino-1-methylquinolinium” returned three records. Beyond the enzyme and analytical papers cited here, the remaining literature consists of cell-culture and rodent pharmacology papers whose framing is outside the scope of this article, which covers identity, enzyme chemistry and analysis. No controlled human studies of 5-Amino-1MQ have been published.

Measuring 5-Amino-1MQ: HPLC and LC-MS/MS

The validated LC-MS/MS method

Awosemo and colleagues developed and validated an LC-MS/MS method for 5-Amino-1MQ (abbreviated 5-AMQ in their paper) in rat plasma and urine [7]. They used protein precipitation, a C18 column with a water and acetonitrile gradient containing 0.1% formic acid, and positive-ion multiple reaction monitoring on a triple-quadrupole instrument, with the transition m/z 159.1 to 90.0. The method was linear from 10 to 2,500 ng/mL, with precision and accuracy within the 15% acceptance range. Applied to a rat pharmacokinetic study, it gave a mean terminal elimination half-life in rat plasma of 3.80 ± 1.10 h after intravenous delivery [7].

Why the cation is easy to see by mass spectrometry

Electrospray ionisation brings molecules from solution into the gas phase as intact ions, usually by adding protons [8]. 5-Amino-1MQ does not need a proton: it is already an ion. The cation appears at its own mass, m/z 159.09, whatever the pH of the mobile phase. The iodide counter-ion does not appear in positive mode, so a positive-mode spectrum confirms the organic cation but says nothing about the salt form.

HPLC purity

Charged analytes can elute early or tail on reversed-phase columns, which is one reason methods add an acidic modifier such as formic acid [7]. The conjugated aminoquinolinium chromophore absorbs strongly in the ultraviolet, so UV detection is sensitive. As with peptides, an HPLC purity figure is a relative area percentage. It does not measure the counter-ion, water or inorganic content. Our explainer on HPLC purity covers how the figure is calculated and what it leaves out, and the same logic applies to small molecules.

Stability chemistry of solid 5-Amino-1MQ

5-Amino-1MQ has no amide bonds to hydrolyse and no asparagine to deamidate. Its reactive points are different:

• The aromatic amine. Aryl amines can oxidise slowly, faster in light.
• The iodide counter-ion. As noted above, iodide can oxidise to iodine in air and light.
• Moisture. Many organic salts take up water from the air. Absorbed water adds mass, lowers the apparent content and can speed other reactions.

The handling conventions are therefore the same as for other sealed research solids: cold, dry and dark, with the vial kept closed until use.

Checking a lot of 5-Amino-1MQ

The published report for 5-Amino-1MQ 50 mg covers batch PS07-5AM50. It was tested by ILS Laboratories in San Diego and dated 08/12/2026. The report was issued to Vortex’s wholesale partner facility for that batch, not commissioned by Vortex, and the /coa/ page labels it as a partner-facility report. The report lists:

• Purity (HPLC): 99.97%, against a specification of at least 95.0%
• Identity (HPLC): confirmed. An HPLC identity test compares retention time with a reference standard. It is weaker evidence than a mass spectrum, which would show the cation at m/z 159.1.
• Net content: 51.54 mg in a vial labelled 50 mg
• Heavy metals (ICP-MS): “All Below Limits” against USP <233>-referenced limits
• Sterility (PCR): “No Growth”
• Endotoxin (LAL): below 0.05 EU/mL
• Fentanyl screen: reported as fentanyl free

The report does not state the salt form, so it does not say whether the 51.54 mg figure refers to the iodide salt or another form. As the table above shows, that choice changes the cation content by almost half. The report can be checked against the original on the lab’s own portal through the verification link on /coa/. For what the contaminant lines mean, see our explainer on sterility and heavy metals testing, and for a field-by-field walk through a report, see how to read a peptide COA.

5-Amino-1MQ is often discussed next to NAD+, because nicotinamide, the NNMT substrate, is also a building block for that coenzyme. The chemistry of NAD+ itself is covered in our NAD+ overview.

Frequently asked questions

Is 5-Amino-1MQ a peptide?

No. 5-Amino-1MQ is a small molecule: a quinoline ring with a methyl group on its nitrogen and an amino group at position 5. It has no amino acid residues and no amide bonds. The cation has a molar mass of about 159.2 g/mol.

What is NNMT?

Nicotinamide N-methyltransferase is a cytosolic enzyme that transfers a methyl group from S-adenosyl-L-methionine to the ring nitrogen of nicotinamide and related pyridines. The products are 1-methylnicotinamide and S-adenosyl-L-homocysteine. Crystal structures of the enzyme with its substrate and with its product have been published.

Why does 5-Amino-1MQ have two CAS numbers?

It is a permanent cation, so it exists as a salt. CAS 685079-15-6 refers to the cation and CAS 42464-96-0 to the iodide salt. The salt has a molar mass of about 286.1 g/mol, of which about 55.6% is the cation.

What does the published 5-Amino-1MQ report show?

The partner-facility report for batch PS07-5AM50, tested by ILS Laboratories and dated 08/12/2026, lists HPLC purity of 99.97%, identity confirmed by HPLC and net content of 51.54 mg. It also lists heavy metals by ICP-MS, a PCR sterility screen, endotoxin below 0.05 EU/mL and a fentanyl screen. It does not state the salt form.

What is the difference between 5-Amino-1MQ iodide and chloride?

Both contain the same 5-amino-1-methylquinolinium cation, C10H11N2+, about 159.2 g/mol. They differ only in the counter-ion. The iodide salt (C10H11IN2, about 286.1 g/mol) is about 55.6% cation by mass, and the chloride salt (C10H11ClN2, about 194.7 g/mol) about 81.8%. Equal milligram amounts of the two salts therefore hold different amounts of the cation, and a lot report should state which salt was tested.

About this article: Written by the Vortex Research Editorial Team. Sources are PubMed-indexed enzyme, structural and analytical studies. Each PMID was checked against PubMed for title, journal and year, and each sentence was matched to the paper’s abstract. Identity data come from PubChem records, quoted without linking. Masses were calculated from atomic composition. The literature count comes from a PubMed search run on 21 October 2026.

Research materials: 5-Amino-1MQ 50mg is supplied as a dry research reagent in a sealed vial. Published lab reports are at /coa/.

References

1. Neelakantan H, Wang HY, Vance V, Hommel JD, McHardy SF, Watowich SJ. Structure-activity relationship for small molecule inhibitors of nicotinamide N-methyltransferase. J Med Chem. 2017;60(12):5015-5028. PMID: 28548833. doi:10.1021/acs.jmedchem.7b00389
2. Iyamu ID, Huang R. Mechanisms and inhibitors of nicotinamide N-methyltransferase. RSC Med Chem. 2021;12(8):1254-1261. PMID: 34458733. doi:10.1039/d1md00016k
3. Peng Y, Sartini D, Pozzi V, Wilk D, Emanuelli M, Yee VC. Structural basis of substrate recognition in human nicotinamide N-methyltransferase. Biochemistry. 2011;50(36):7800-7808. PMID: 21823666. doi:10.1021/bi2007614
4. Swaminathan S, Birudukota S, Thakur MK, et al. Crystal structures of monkey and mouse nicotinamide N-methyltransferase (NNMT) bound with end product, 1-methyl nicotinamide. Biochem Biophys Res Commun. 2017;491(2):416-422. PMID: 28720493. doi:10.1016/j.bbrc.2017.07.087
5. Neelakantan H, Vance V, Wang HL, McHardy SF, Watowich SJ. Noncoupled fluorescent assay for direct real-time monitoring of nicotinamide N-methyltransferase activity. Biochemistry. 2017;56(6):824-832. PMID: 28121423. doi:10.1021/acs.biochem.6b01215
6. Loring HS, Thompson PR. Kinetic mechanism of nicotinamide N-methyltransferase. Biochemistry. 2018;57(38):5524-5532. PMID: 30148963. doi:10.1021/acs.biochem.8b00775
7. Awosemo O, Neelakantan H, Watowich S, et al. Development & validation of LC-MS/MS assay for 5-amino-1-methyl quinolinium in rat plasma: application to pharmacokinetic and oral bioavailability studies. J Pharm Biomed Anal. 2021;204:114255. PMID: 34304009. doi:10.1016/j.jpba.2021.114255
8. Fenn JB, Mann M, Meng CK, Wong SF, Whitehouse CM. Electrospray ionization for mass spectrometry of large biomolecules. Science. 1989;246(4926):64-71. PMID: 2675315. doi:10.1126/science.2675315

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