How are ACTH and alpha-MSH related?

Alpha-MSH corresponds to the first 13 residues of ACTH, acetylated at the N-terminus and amidated at the C-terminus.

Why does older literature say 'MSH/ACTH 4-10'?

Because residues 4 to 10 belong to both hormones, so for that region the distinction does not arise.

Semax (ACTH Fragment Peptide)

Where ACTH, Alpha-MSH and Beta-Endorphin All Come From

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-233 cited sources

Proopiomelanocortin is a precursor protein cleaved into several signalling peptides including ACTH, alpha-melanocyte-stimulating hormone and beta-endorphin. Which products emerge depends on which processing enzymes a tissue expresses, so one gene yields a stress hormone in one tissue and a pigmentation signal in another.

Key facts

Precursor: Proopiomelanocortin (POMC)
Products include: ACTH, alpha-MSH, beta-endorphin
Determined by: Tissue-specific processing enzymes
alpha-MSH relationship: ACTH(1-13), acetylated and amidated
Evolution review: Dores 2011 (PMID 21388402)
Relevant here: Semax, MT-2 and KPV all derive from it

Why one gene yields several hormones

Making one long precursor and cutting it differently in different places is an efficient design. The same transcript can produce a stress hormone in one tissue and a pigmentation signal in another, with the outcome determined by which prohormone convertases that tissue expresses rather than by which gene is transcribed.

The relationship between ACTH and alpha-MSH

Alpha-MSH corresponds to the first thirteen residues of ACTH, with an acetyl group added at the N-terminus and the C-terminus amidated. It is not a separate sequence that happens to resemble ACTH — it is the same stretch of the precursor, released by a further cleavage and then chemically capped at both ends.

Research material referenced

Semax 10mg — third-party HPLC tested

View — £24.99

Why the older literature writes MSH/ACTH

Because for the shared region the distinction does not arise. Sandman and colleagues published in the Journal of Clinical Endocrinology and Metabolism in 1977 on MSH/ACTH 4-10 and measures of attention — writing both names because residues 4 to 10 belong to both hormones. That notation is a direct record of the structural relationship.

What the capping changes

N-terminal acetylation and C-terminal amidation both remove a charged group. That alters receptor preference and, importantly, removes the free termini exopeptidases require — the same protective logic seen in MT-2, which carries both modifications deliberately. Processing is not merely cutting; it is finishing.

The evolutionary picture

Dores reviewed the origin, phylogeny and post-translational processing of POMC and the melanocortins in the Annals of the New York Academy of Sciences in 2011. The system is ancient and conserved, which is part of why the same short sequences recur across so many species and why fragments of them have been studied for decades.

Why this matters for reading this catalogue

Three separate product categories on this site — Semax, MT-2 and KPV — descend from this one precursor region. They are sold and described independently, and structurally they are neighbouring or overlapping pieces of the same short hormone. Nothing supplied here is a licensed medicine and no claim is made about any of them.

Extended research context

The Semax (ACTH Fragment Peptide) deep dive

Deep dive: what the Pro-Gly-Pro extension actually accomplishes

Semax is built from a four-residue fragment of ACTH with Pro-Gly-Pro appended, and that appendix does two separate jobs at once. Proline is the only proteinogenic amino acid whose side chain bonds back to its own backbone nitrogen, forming a ring that removes the amide hydrogen and locks rotation. Proteolytic enzymes generally need an extended, rotatable backbone at their active site, so bonds near proline are poor substrates for most of them — which is why proline-rich motifs recur throughout stabilised peptide design. The second job is subtractive: Pro-Gly-Pro occupies the positions where ACTH carries Arg-Trp-Gly, and those are the residues contributing to the parent hormone's adrenal-stimulating activity. One substitution therefore buys protease resistance and removes an unwanted pharmacology, which is unusually economical design.

Deep dive: the naming point worth getting right

Semax is near-universally described as an ACTH(4-10) analogue, and peer-reviewed paper titles use that phrase. Structurally it is not quite that. ACTH residues 4 to 10 are Met-Glu-His-Phe-Arg-Trp-Gly; Semax is Met-Glu-His-Phe-Pro-Gly-Pro. The first four residues match and the last three are wholly different — replacement rather than modification. PubChem, indexing by structure rather than design lineage, records it as ACTH(4-7) plus Pro-Gly-Pro. Neither name is wrong, but the loose one obscures the fact that the substituted segment is precisely the functionally consequential part.

Deep dive: reading an unevenly distributed evidence base

Semax's roughly 231 indexed records split along an unusual line. Mechanistic work — BDNF and trkB expression in rat hippocampus, transcriptomics in focal cerebral ischaemia, neurotrophin dynamics across brain regions — appears in international journals in English and can be assessed directly. Clinical work is concentrated in Russian-language publications, principally the Korsakov Journal of Neurology and Psychiatry, indexed by translated title and often without accessible English full text, much of it predating current standards for pre-registration and reporting. The honest position is that this is evidence which is difficult to verify independently, which is a different thing from evidence that is absent, and a different thing again from evidence that is established.

Research applications

▸Neurotrophin expression research (BDNF, NGF, TrkB, TrkA)
▸Neuroprotection and cerebral ischaemia models
▸Study of proline-stabilised peptide design
▸Comparative work on ACTH fragments without steroidogenic activity
▸Transcriptomic profiling in rodent brain models

Handling checklist

✓Store lyophilised material cold, dry and protected from light
✓Expect methionine oxidation as the degradation route (+16 Da; only one Met, so not +32)
✓No reducing agent needed — the sequence contains no cysteine
✓Introduce diluent gently against the vial wall; swirl rather than shake
✓Aliquot to avoid repeated freeze-thaw cycles
✓Check whether a certificate reports net peptide content or gross salt weight

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Describing Semax as ACTH(4-10) without qualification

Fix: It shares only residues 4-7; Pro-Gly-Pro replaces Arg-Trp-Gly, and that replacement is the design's whole point.

✗ Treating Russian registration as equivalent to MHRA approval

Fix: Authorisations are jurisdictional and do not transfer. Semax has never been assessed by the MHRA, EMA or FDA.

✗ Reading a BDNF expression change as a demonstrated outcome

Fix: The studies measured gene and protein expression in rats. Expression is upstream of function and upstream again of any clinical claim.

✗ Assuming a named receptor exists

Fix: No primary receptor has been definitively established; the literature characterises downstream effects more confidently than the initiating event.

✗ Expecting ACTH-like adrenal effects

Fix: Semax does not stimulate adrenal steroidogenesis — the responsible residues were substituted out.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

What is POMC?: Proopiomelanocortin, a precursor protein cleaved into several signalling peptides including ACTH, alpha-MSH and beta-endorphin.
How are ACTH and alpha-MSH related?: Alpha-MSH corresponds to the first 13 residues of ACTH, acetylated at the N-terminus and amidated at the C-terminus.
Why does older literature say 'MSH/ACTH 4-10'?: Because residues 4 to 10 belong to both hormones, so for that region the distinction does not arise.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

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