5-Amino-1MQ: Molecular Structure

Molecular Structure#

5-Amino-1MQ (5-amino-1-methylquinolinium) is a small organic molecule, not a peptide. Despite being commonly discussed in peptide research contexts, it lacks an amino acid chain structure. Instead, it is based on a quinolinium scaffold -- a bicyclic aromatic ring system containing nitrogen.

Chemical Identity#

Structural Features#

The molecule consists of:

• Quinoline core: A fused benzene-pyridine ring system providing the aromatic scaffold
• N-methylation at position 1: A methyl group on the ring nitrogen, creating the quaternary ammonium (quinolinium) cation. This is critical for NNMT substrate site recognition
• Amino group at position 5: A primary amine on the quinoline ring that contributes to membrane permeability and biological activity

The 1-methylquinolinium scaffold mimics the structure of 1-methylnicotinamide (1-MNA), the product of NNMT's enzymatic reaction. This structural similarity allows 5-Amino-1MQ to bind competitively at the NNMT substrate site.

Chemical Properties#

Target Selectivity#

5-Amino-1MQ is a substrate-competitive NNMT inhibitor with notable selectivity:

• NNMT IC50: Approximately 1.2 microM
• GNMT (glycine N-methyltransferase): No significant inhibition
• HNMT (histamine N-methyltransferase): No significant inhibition
• NAMPT (nicotinamide phosphoribosyltransferase): No inhibition
• NMNAT (nicotinamide mononucleotide adenylyltransferase): No inhibition

This selectivity means 5-Amino-1MQ blocks NNMT without directly interfering with other methyltransferases or NAD+ salvage enzymes, reducing the likelihood of off-target effects on methylation pathways -- at least in preclinical models.

Membrane Permeability#

The compound demonstrates high passive membrane diffusion and active transport permeability, as characterized in the original Neelakantan et al. (2018) study. The combination of the cationic quinolinium core and the amino substituent appears to facilitate cellular uptake.

Structure-Activity Relationships#

The Neelakantan et al. (2018) study evaluated a series of 1-methylquinolinium derivatives with various substitutions. Key findings:

• Primary amine substitutions (as in 5-Amino-1MQ) displayed the best combination of NNMT inhibition and membrane permeability
• The position 5 amino group was critical for the balance of potency and cellular uptake
• Other substitution patterns showed reduced activity or permeability

Stability Characteristics#

Limited stability data has been published for 5-Amino-1MQ. As a quaternary ammonium compound:

• The dry salt form is expected to be stable under standard storage conditions (-20 degrees C, protected from light and moisture)
• Solution stability has not been formally characterized in published literature
• The iodide salt form is the most commonly available from commercial suppliers