5-Amino-1MQ is 5-amino-1-methylquinolin-1-ium, a permanently charged quaternary heteroaromatic cation normally supplied as the iodide salt. It is not a peptide and shares no structural relationship with the rest of this category: it is a single fused-ring small molecule of 159 Da as the free cation. Its target is nicotinamide N-methyltransferase, the cytosolic enzyme that transfers a methyl group from S-adenosylmethionine to nicotinamide to yield 1-methylnicotinamide, and the compound acts as a nicotinamide-mimetic, membrane-permeable inhibitor of that reaction.

Because that reaction consumes both nicotinamide, a substrate of the NAD+ salvage pathway, and S-adenosylmethionine, the principal cellular methyl donor, NNMT sits at the junction of NAD+ and methyl-group metabolism; its expression is high in adipose tissue and liver. The best-characterised pharmacological work is Neelakantan et al., 'Selective and membrane-permeable small molecule inhibitors of nicotinamide N-methyltransferase reverse high fat diet-induced obesity in mice', Biochemical Pharmacology, 2018, which reported the design of this inhibitor series and studied it in diet-induced obese mice.

The human evidence base is empty. There are no published human administration studies, and the rodent literature is preclinical proof-of-concept for a target rather than a characterised compound with pharmacokinetic or safety data. The quaternary ammonium centre also matters commercially: the free cation and each of its salts are distinct chemical entities, and the registry number, formula and mass given here describe the iodide specifically.