Function
While Humanin exerts neuroprotective and cytoprotective effects in models of Alzheimer’s disease, ischemia, and metabolic stress, reducing apoptosis and improving cell survival7136141, Melanotan II is studied as a tanning and libido-enhancing agent; increases melanin production and can reduce food intake and modulate sexual arousal in animal models and humans3545.
Mechanism
While Humanin works as a mitochondrial-derived 24-amino-acid peptide that protects cells against diverse apoptotic insults by interacting with cell-surface cytokine receptor complexes and intracellular targets, thereby activating pro-survival STAT3 and other pathways7136141, Melanotan II is a cyclic heptapeptide melanocortin analog (Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2) that acts as a non-selective, high-potency agonist at MC1R, MC3R, MC4R, and MC5R, influencing pigmentation, appetite, and sexual behavior3545.
Length and Sequence
Humanin is 24 amino acids long, whereas Melanotan II is shorter as it has a length of 7 amino acids. Humanin is made up of a sequence of Methionine, Alanine, Proline, Arginine, Glycine, Phenylalanine, Serine, Cysteine, Leucine, Leucine, Leucine, Leucine, Leucine, Threonine, Serine, Glutamic acid, Isoleucine, Aspartic acid, Leucine, Proline, Valine, Lysine, Arginine, Arginine, Alanine. Melanotan II is made up of a sequence of Nle, Aspartic acid, Histidine, Phenylalanine, Arginine, Tryptophan, Lysine.