Apamin

Chemical Identity

Property	Value
Chemical Formula	C79H131N31O24S4
Molecular Weight	2027 Da
CAS Number	24345-16-2
Peptide Class	Bee Venom Neurotoxin (18 amino acids)
Sequence	CNCKAPETALCARRCQQH-NH2
Disulfide Bonds	2 (Cys1-Cys11, Cys3-Cys15)
Origin	Apis mellifera (honeybee)

Structure

Apamin is an 18-amino acid bee venom peptide with two disulfide bonds forming a compact structure. It is the smallest known neurotoxic peptide. The rigid cage-like structure is essential for its ability to cross the blood-brain barrier and block neuronal potassium channels.

Mechanism of Action

Apamin selectively blocks small-conductance calcium-activated potassium channels (SK1, SK2, SK3) by binding to the external vestibule of the channel pore. This inhibition increases neuronal excitability by preventing the afterhyperpolarization that follows action potentials. SK2 selectivity makes it a valuable neuroscience research tool.

Clinical Applications

• Research tool: SK channel characterization in neuroscience
• Neuroscience: Studying neuronal excitability and learning/memory
• Movement disorders: SK channel modulators for ataxia
• Bee venom therapy: Component of apitherapy

Pharmacokinetics

• Half-life: ~20 minutes (IV)
• Blood-brain barrier: Crosses readily
• Route: Research use (IV, intracerebroventricular)
• Potency: Active at nanomolar concentrations

Safety and Side Effects

Neurotoxicity (convulsions, hyperexcitability), respiratory failure at high doses, and potential anaphylaxis. Therapeutic index is narrow. Primarily used as a research reagent rather than therapeutic.

References

• Habermann, E. (1972). Bee and wasp venoms. Science, 177, 314-322.
• Stocker, M. (2004). Ca(2+)-activated K+ channels: molecular determinants and function of the SK family. Nature Reviews Neuroscience, 5, 758-770.