Somatostatin-20: natural growth-hormone-slowing peptide
A naturally occurring gut peptide from the somatostatin family that signals the pituitary gland to slow growth hormone release; used as a lab research tool.
- Class
- Endogenous somatostatin-family peptide (porcine-isolated extended form)
- Status
- No approved therapeutic status identified in attached sources
- Main caveat
- Source file contains a chemical identity record only; no efficacy, mechanism, safety, or regulatory evidence is attached
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
What this is
Somatostatin-20 is a naturally occurring, 20-residue peptide belonging to the somatostatin family — the group of signalling peptides best known for telling the pituitary gland to hold back growth hormone. It was first isolated from porcine (pig) duodenal tissue in 1984, purified alongside two close relatives, somatostatin-28 and somatostatin-25 (Arakawa and colleagues, 1984). Unlike the canonical 14-amino-acid form of somatostatin (SST-14) that was discovered more than a decade earlier, somatostatin-20 carries an extra six amino-acid tail at its N-terminus — hence the larger residue count and the "NH₂-terminally extended" label used in the original characterisation. The stored 20-letter sequence (APRERKAGCKNFFWKTFTSC) represents the backbone; SST-20 contains an intramolecular disulfide bond between its two cysteine residues, forming the same constrained ring that is central to somatostatin family receptor activity, but this bond is not visible in the linear sequence shown here.
History
Somatostatin itself was first characterised in 1973 by Brazeau and colleagues from ovine hypothalamic extracts, where it was found to potently inhibit growth-hormone release. Over the following decade it became clear that the gut and other peripheral tissues produce a wider range of somatostatin-family peptides than the hypothalamus alone. In 1980, a 28-residue form (somatostatin-28) was isolated from porcine hypothalamus and recognised as a probable precursor. Arakawa and colleagues then reported in 1984, in Life Sciences, that porcine duodenum contains at least three additional extended forms simultaneously — somatostatin-25, somatostatin-28, and the newly characterised somatostatin-20 — establishing that the gastrointestinal tract processes the prosomatostatin precursor into a broader set of molecular forms than previously appreciated (Arakawa and colleagues, 1984).
What it does
Somatostatin-20 is a member of the somatostatin peptide family, whose defining feature is broad inhibition of secretion: growth hormone from the pituitary, insulin and glucagon from the pancreas, gastrin, gastric acid, and a range of other gastrointestinal hormones. All somatostatin family peptides exert these effects by binding to somatostatin receptors (SSTR1–5), a family of G-protein-coupled receptors that are expressed widely across the brain, pituitary, pancreas, and gut. The pharmacologically active core of somatostatin-20 — the Phe-Trp-Lys-Thr motif within the disulfide-constrained ring — is identical to that of SST-14, which is required for high-affinity binding across SSTR subtypes. The six additional N-terminal residues in somatostatin-20 distinguish it from SST-14 but are analogous to the N-terminal extension present in somatostatin-28, a form with documented preferential affinity for SSTR5. Whether somatostatin-20's own N-terminal extension confers equivalent subtype selectivity has not been reported in the available literature.
Evidence
- Human: No human clinical data are reported in the literature for somatostatin-20 specifically. Clinical research on the somatostatin family has focused on SST-14 itself and on synthetic analogs (octreotide, lanreotide, pasireotide).
- Animal: Somatostatin-20 was isolated and characterised from porcine duodenal tissue. No animal pharmacological data specific to the SST-20 form are reported in the available dossier literature.
- In vitro: Somatostatin-20 was co-isolated with somatostatin-28 and somatostatin-25 from porcine duodenum (Arakawa and colleagues, 1984). No receptor-binding or functional potency data specific to the somatostatin-20 form appear in the available dossier sources.
Mechanism
Somatostatin family peptides signal through five receptor subtypes (SSTR1–5), all of which are Gi/o-coupled GPCRs. Activation primarily inhibits adenylate cyclase, reducing intracellular cAMP; this is the principal mechanism by which pituitary growth-hormone secretion is suppressed. SSTRs also open inwardly rectifying K⁺ channels and suppress voltage-gated Ca²⁺ entry, collectively dampening secretory cell excitability. SSTR2 and SSTR5 are the predominant subtypes governing growth-hormone regulation, while SSTR5 shows markedly higher affinity for the N-terminally extended somatostatin-28 relative to SST-14; because somatostatin-20 shares structural features of both forms, it is a logical candidate for receptor-selectivity studies, though no such data are reported in the primary literature to date.
The structural basis for receptor engagement is the conserved disulfide-bridged ring containing the Phe-Trp-Lys-Thr tetrapeptide pharmacophore. In somatostatin-20, the two cysteine residues that form this bridge correspond to positions 7 and 20 of the stored sequence (APRERKAGCKNFFWKTFTSC); the linear sequence does not represent the bioactive conformation.
Open questions
- No binding-affinity data (Ki or IC50) at any SSTR subtype have been published for somatostatin-20 as a distinct ligand — the relative potency compared with SST-14 and SST-28 remains uncharacterised.
- It is unclear whether somatostatin-20 is secreted as a discrete biologically active form in vivo or exists primarily as a tissue-specific processing intermediate of prosomatostatin.
- The functional significance of the six-residue N-terminal extension relative to the SST-14 core has not been probed for SST-20 specifically.
- Species conservation of the SST-20 cleavage site across mammals beyond porcine tissue has not been systematically documented.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does the short positive tail that distinguishes SST-20 from the standard somatostatin molecule make it grab a different receptor?
If true, it could explain why gut-derived somatostatin-20 behaves differently from brain somatostatin, and might inspire drugs that selectively target appetite or growth-hormone circuits without hitting unintended receptors.
Could SST-20 dampen hunger and growth-hormone pulses without fully triggering the ghrelin receptor?
If SST-20 is a partial activator of the ghrelin receptor, it could serve as a natural blueprint for drugs that reduce appetite or excessive growth-hormone levels with fewer side effects than full agonists or full blockers.
Does swapping one proline for another amino acid change which receptor SST-20 targets?
If a single residue swap can redirect SST-20 between receptors, drug designers could use this peptide as a starter scaffold to quickly generate receptor-specific drugs for conditions like acromegaly, carcinoid tumors, or obesity.
Is SST-20 made exclusively in the gut because the enzymes that process somatostatin work differently there?
If SST-20 is a gut-exclusive signal, it could explain why gut surgery changes hormone and appetite regulation in unexpected ways, and might open a new class of gut-targeted therapies for obesity or hormonal tumors that avoid brain side effects.
Could SST-20 suppress excess growth hormone better than current drugs by acting on both known receptors that control it?
If this holds, patients with acromegaly or growth-hormone-secreting tumors who respond incompletely to existing drugs might benefit from SST-20-derived therapies that close a molecular loophole current treatments miss.
Could locking SST-20 into a rigid two-ring shape make it stable enough and precise enough to work as a drug?
If this engineering approach works, it could yield a new kind of somatostatin drug that lasts longer in the body and targets two receptor types at once, potentially helping patients with tumors or hormone excess conditions who do not respond well to current single-receptor treatments.
▸full evidence table2 metrics
| metric | value | tool |
|---|---|---|
| ipTM | 0.8631913065910339 | boltz-2 |
| ranking score | 0.807591438293457 | boltz-2 |
▸structural qualityopenfold3
| metric | value | note |
|---|---|---|
| gpde | 0.644 | global PDE — lower = better |
| disorder | NaN | fraction disordered |
▸3-letter notation
▸recipeboltz-2 1.0
| parameter | value |
|---|---|
| model | boltz-2 1.0 |
| weights | — |
| hardware | nvidia_nim_api |
| mlx version | — |
| python | — |
| random seed | — |
| msa strategy | none |
| diffusion samples | 1 |
| runtime | — |
| predicted by | mlx@peptide |
| predicted at | 2026-04-24 |
▸citationbibtex
@peptide{pep10493,
sequence = {APRERKAGCKNFFWKTFTSC},
target = {ghsr},
author = {peptidemodel},
year = {2026},
status = {synthesized}
}