Page data last changed: . Registry refreshes and identity assessments are separate from scientific content review.
The smallest known neurotoxic peptide, and the defining pharmacological probe for SK potassium channels.
Also known as: apamine
Part of the Foundational & therapeutic peptides cluster
Overview
Apamin is an 18-amino-acid neurotoxic peptide from honeybee venom, cross-linked by two disulfide bonds into a compact fold. It is the classic selective blocker of small-conductance calcium-activated potassium (SK) channels, so it is used throughout neuroscience to dissect the afterhyperpolarization that follows neuronal firing. This page is educational and not medical advice.
Source & context
Biological / chemical source: Honeybee venom (Apis mellifera)
Primary research or clinical context: Widely used pharmacological research tool for SK-channel physiology
SK-channel probe
By blocking SK channels, apamin removes part of the potassium current that normally repolarizes neurons after an action potential, increasing excitability. Its high selectivity made it the reference tool for identifying SK channels and studying their role in rhythmic firing, synaptic plasticity and muscle activity.
Context and cautions
Apamin makes up a few percent of dry bee venom and is a potent neurotoxin, so it is handled strictly as a laboratory reagent. Researchers have examined SK-channel modulation in memory and movement disorders, but such work is exploratory. This page provides educational background only.
Sequence of the selected reference form
Sequence backbone for the reference form: Mature apamin, two disulfides and His18-amide. Termini, stereochemistry and modifications are described below.
Structure & chemistry
Molecular identity & reference confidence
Source-supported reference
Reviewed UniProt specifies the18-residue mature chain, His-amide and the two disulfides, corroborated by the GSRS protein definition and the original folding paper. PubChem16133797 and16218850 have exactly identical standard InChI, not merely equal masses; their different imidazole naming does not establish a different molecular form. These ancillary attributes conflict with the annotated two disulfides and terminal amidation and are not used. The exact PubChem formulaC79H131N31O24S4 matches independent atom accounting of those modifications.
- Molecular form
- Mature apamin, two disulfides and His18-amide
- Species
- Apis mellifera
- Termini (N / C)
- Free Cys amino terminus / His carboxamide
Average reference mass · Molecular identity assessment: 2026-10-05
Reference policy updated: 2026-10-05
- PubChem PUG molecular properties, CID 16133797 · 2026-10-05
- PubChem structure-derived biologic notation, CID 16133797 · 2026-10-05
- Reviewed UniProtKB P01500 · 2026-10-05
- NIH NCATS/FDA GSRS apamin complete protein definition · 2026-10-05
- Original apamin folding study (1992) · 2026-10-05
H-Cys(1)-Asn-Cys(2)-Lys-Ala-Pro-Glu-Thr-Ala-Leu-Cys(1)-Ala-Arg-Arg-Cys(2)-Gln-Gln-His-NH2
- Molecular formula
- C79H131N31O24S4
- Average reference mass
- ≈ 2,027.4
- Backbone
- Mature apamin, two disulfides and His18-amide
- C-terminus
- His carboxamide
- PubChem CID: 16133797
- UNII: X644P85KUR
Chemistry values: curated profile, PubChem.
Apamin — reconstitution calculator
Enter how much peptide is in the vial and how much diluent (e.g. bacteriostatic water) is added. The tool returns the resulting solution concentration — and, for any amount you type, the volume it corresponds to. This is educational arithmetic, not a dosing recommendation.
Reference form: Mature apamin, two disulfides and His18-amideAverage reference mass: 2,027.4 Da
Enter an amount to see the volume it corresponds to.
Educational concentration mathematics only. This tool does not recommend a dose, amount, or protocol, and nothing here is medical advice. Many peptides are not authorized by Health Canada for human use — see our reconstitution and bacteriostatic-water guides for context.
FAQ about Apamin
What is Apamin?+
Apamin is an 18-amino-acid neurotoxic peptide from honeybee venom, cross-linked by two disulfide bonds into a compact fold. It is the classic selective blocker of small-conductance calcium-activated potassium (SK) channels, so it is used throughout neuroscience to dissect the afterhyperpolarization that follows neuronal firing. This page is educational and not medical advice.
What Canadian product status is recorded for Apamin?+
Canadian product status for Apamin has not been verified in this profile. No verified record here does not mean no authorization exists. Status depends on the product, formulation and use; consult Health Canada's product records.
What is the length of the selected reference form for Apamin?+
The selected reference form (Mature apamin, two disulfides and His18-amide) has 18 residues or residue-derived units in its backbone. Other forms in this family may have a different length.
Related peptides
References & further reading
- 1.Habermann (1984). Apamin. Pharmacol Ther
- 2.Kuzmenkov et al. (2022). Apamin structure and pharmacology revisited. Front Pharmacol
- 3.Gu et al. (2020). Therapeutic Effects of Apamin as a Bee Venom Component for Non-Neoplastic Disease. Toxins (Basel)
- 4.Jang et al. (2023). Protective Effects of Apamin on Acetaminophen-Induced Hepatotoxicity in Mice. Curr Issues Mol Biol
- 5.Kim et al. (2021). Apamin Enhances Neurite Outgrowth and Regeneration after Laceration Injury in Cortical Neurons. Toxins (Basel)
- 6.Regnier-Vigouroux et al. (1989). Structural analysis of the interaction of apamin with Ia and its recognition by Ad- or Ab-restricted mouse T cells. J Immunol
- 7.Yu et al. (2014). Apamin does not inhibit human cardiac Na+ current, L-type Ca2+ current or other major K+ currents. PLoS One
- 8.Laurindo et al. (2024). The therapeutic potential of bee venom-derived Apamin and Melittin conjugates in cancer treatment: A systematic review. Pharmacol Res
- 9.UniProtKB — Apamin, Apis mellifera (P01500)
- 10.Wikipedia — Apamin