Melanocortin-related peptides

The melanocortins are peptides cut from pro-opiomelanocortin (POMC), among them ACTH and the melanocyte-stimulating hormones, which share the core sequence His-Phe-Arg-Trp. α-MSH, the first 13 residues of ACTH acetylated and amidated, is the reference sequence here. Synthetic relatives range from its C-terminal tripeptide (KPV) to a cyclic analog with D-phenylalanine in the core (PT-141) and an ACTH fragment extended with Pro-Gly-Pro (Semax).

Members compared

Calculated from each structure

Peptide	Residues	Formula	Monoisotopic mass (Da)	Charge, pH 7	pI	Termini
KPV	3	C16H30N4O4	342.2267	1.0	9.70	free amine; free acid
PT-141	7	C50H68N14O10	1,024.5243	0.2	9.50	N-acetyl; free acid
Semax	7	C37H51N9O10S	813.3480	-0.8	5.36	free amine; free acid
α-MSH	13	C77H109N21O19S	1,663.7929	1.2	10.44	N-acetyl; amide

Sequences and relationships

Each member's sequence in three-letter code, and how it relates to α-MSH, worked out position by position from the structures. Members with no entry in the last column are not direct sequence relatives of α-MSH.

Relationship to α-MSH

Peptide	Sequence	Relationship
KPV	H-Lys-Pro-Val-OH	Residues 11–13 of α-MSH; N-terminus free amine (reference: N-acetyl); C-terminus free acid (reference: amide)
PT-141	Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-OH	—
Semax	H-Met-Glu-His-Phe-Pro-Gly-Pro-OH	—
α-MSH	Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2	Reference sequence

Shared analytical features

The sequence-specific variants from each member's entry, counted across the family: what an HPLC or mass spectrometry result for these peptides is most often read against.

Variants by number of members

Variant	Members
Methionine oxidation	2 of 4: Semax, α-MSH
Tryptophan oxidation	2 of 4: PT-141, α-MSH
C-terminal amide	1 of 4: α-MSH
Stereochemistry	1 of 4: PT-141

Every member can also carry the synthesis-related variants common to all synthetic peptides, described in How synthetic peptides are made.

Pairs compared in detail

• α-MSH and KPV compared

Sources & Further Reading

1. Prohaska T, Irrgeher J, Benefield J, Böhlke JK, Chesson LA, Coplen TB, et al. Standard atomic weights of the elements 2021 (IUPAC Technical Report). Pure and Applied Chemistry 2022;94(5):573–600. doi:10.1515/pac-2019-0603
2. Wang M, Huang WJ, Kondev FG, Audi G, Naimi S. The AME 2020 atomic mass evaluation (II). Tables, graphs and references. Chinese Physics C 2021;45(3):030003. doi:10.1088/1674-1137/abddaf
3. Rice P, Longden I, Bleasby A. EMBOSS: the European Molecular Biology Open Software Suite. Trends in Genetics 2000;16(6):276–277. doi:10.1016/S0168-9525(00)02024-2
4. Pace CN, Vajdos F, Fee L, Grimsley G, Gray T. How to measure and predict the molar absorption coefficient of a protein. Protein Science 1995;4(11):2411–2423. doi:10.1002/pro.5560041120
5. Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein. Journal of Molecular Biology 1982;157(1):105–132. doi:10.1016/0022-2836(82)90515-0
6. Meija J, Coplen TB, Berglund M, Brand WA, De Bièvre P, Gröning M, et al. Isotopic compositions of the elements 2013 (IUPAC Technical Report). Pure and Applied Chemistry 2016;88(3):293–306. doi:10.1515/pac-2015-0503
7. Roepstorff P, Fohlman J. Letter to the editors: proposal for a common nomenclature for sequence ions in mass spectra of peptides. Biomedical Mass Spectrometry 1984;11(11):601. doi:10.1002/bms.1200111109
8. Biemann K. Contributions of mass spectrometry to peptide and protein structure. Biomedical and Environmental Mass Spectrometry 1988;16(1–12):99–111. doi:10.1002/bms.1200160119
9. Geiger T, Clarke S. Deamidation, isomerization, and racemization at asparaginyl and aspartyl residues in peptides. Succinimide-linked reactions that contribute to protein degradation. Journal of Biological Chemistry 1987;262(2):785–794. doi:10.1016/S0021-9258(19)75855-4
10. Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharmaceutical Research 2010;27(4):544–575. doi:10.1007/s11095-009-0045-6
11. D'Hondt M, Bracke N, Taevernier L, Gevaert B, Verbeke F, Wynendaele E, et al. Related impurities in peptide medicines. Journal of Pharmaceutical and Biomedical Analysis 2014;101:2–30. doi:10.1016/j.jpba.2014.06.012

Cosmic Peptides. (2026, October 25). Melanocortin-related peptides. Cosmic Peptides Research Library. Retrieved October 26, 2026, from https://cosmicpeptides.com/research/peptides/families/melanocortin

@misc{cosmicpeptides_research_peptides_families_melanocortin,
  author       = {{Cosmic Peptides}},
  title        = {Melanocortin-related peptides},
  howpublished = {Cosmic Peptides Research Library},
  year         = {2026},
  month        = oct,
  url          = {https://cosmicpeptides.com/research/peptides/families/melanocortin},
  urldate      = {2026-10-26},
  note         = {Last reviewed 2026-10-25}
}

TY  - ELEC
AU  - Cosmic Peptides
TI  - Melanocortin-related peptides
T2  - Cosmic Peptides Research Library
PB  - Cosmic Peptides
PY  - 2026
DA  - 2026/10/25
UR  - https://cosmicpeptides.com/research/peptides/families/melanocortin
Y2  - 2026/10/26
LA  - en
ER  -