Function
While GHRP-2 is used in research to induce robust GH pulses and study anabolic and metabolic effects; clinically developed as pralmorelin for GH deficiency diagnostics6272, Melanotan I is approved in some regions for prevention of phototoxicity in erythropoietic protoporphyria and is studied as a skin-darkening, photoprotective peptide3444.
Mechanism
While GHRP-2 works as a second-generation hexapeptide growth hormone–releasing peptide that mimics ghrelin by agonizing GHSR-1a, strongly stimulating pulsatile GH release and modestly raising prolactin, ACTH, and cortisol62723096, Melanotan I is a linear 13-amino-acid analog of α-MSH (afamelanotide) that selectively activates MC1R on melanocytes, increasing eumelanin synthesis and providing photoprotection3444.
Length and Sequence
GHRP-2 is 6 amino acids long, whereas Melanotan I is longer as it has a length of 13 amino acids. GHRP-2 is made up of a sequence of Alanine, D-2-Nal, Alanine, Tryptophan, Phenylalanine, Lysine. Melanotan I is made up of a sequence of Serine, Tyrosine, Serine, Nle, Glutamic acid, Histidine, Phenylalanine, Arginine, Tryptophan, Glycine, Lysine, Proline, Valine.