Function
While Acetyl tetrapeptide-5 is used in cosmetic eye formulations to decrease puffiness, eye bags, and dark circles by reducing edema and protecting proteins such as SOD from glycation51150159154, 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 Acetyl tetrapeptide-5 works as a synthetic tetrapeptide, Ac-βAla-His-Ser-His (Eyeseryl), with reported ACE-1 inhibition and anti-glycation activity, proposed to improve microcirculation and reduce capillary permeability and fluid accumulation in periorbital tissues51150159157, 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
Acetyl tetrapeptide-5 is 4 amino acids long, whereas Melanotan I is longer as it has a length of 13 amino acids. Acetyl tetrapeptide-5 is made up of a sequence of βAla, Histidine, Serine, Histidine. Melanotan I is made up of a sequence of Serine, Tyrosine, Serine, Nle, Glutamic acid, Histidine, Phenylalanine, Arginine, Tryptophan, Glycine, Lysine, Proline, Valine.