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Most toxic natural peptide
α-Amanitin
~0.1 mg/kg
Bicyclic octapeptide · MW 919 Da · Amanita phalloides
The estimated lethal dose for humans is around 0.1 mg per kilogram of body weight. α-Amanitin inhibits RNA polymerase II, halting gene transcription in liver cells. No antidote exists. Symptoms are delayed 6–24 hours, by which time severe liver damage has already begun.
Source: Wieland T. (1983) Peptides of Poisonous Amanita Mushrooms. Springer.
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Fastest-acting venom peptide
Conus geographus venom
< 5 min
Conantokin-G · Conotoxins · 10–30 residues
The geography cone snail's venom cocktail — targeting sodium, calcium, and potassium channels simultaneously — can cause death within minutes. Its 'lightning-strike cabal' conotoxins cause immediate paralysis, and it has killed more humans than any other cone snail.
Source: Olivera BM. (2006) Conus peptides: biodiversity-based discovery and exogenomics. J Biol Chem.
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Smallest biologically active peptide hormone
TRH (Thyrotropin-releasing hormone)
3 aa
pGlu-His-Pro-NH₂ · MW 362 Da · Hypothalamus
TRH is just three amino acids yet functions as a complete hormone — travelling through the blood to trigger TSH release from the pituitary. The smallest peptide hormone in the human body. Its pyroglutamate N-terminus protects it from peptidase degradation.
Source: Guillemin R. (1978) Nobel Lecture — Peptides in the Brain. Science.
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Most expensive peptide drugs (synthesis cost)
Ziconotide
$100K+ /g
Ziconotide: 25 aa · 3 disulfide bonds · Conus magus
Ziconotide requires 25 amino acid couplings plus 3 precisely-configured disulfide bonds — any error wastes the entire batch, which is why reported synthesis costs run to six figures per gram. Fatty-acid conjugation and the extra purification steps it needs make lipidated peptides among the most expensive active ingredients manufactured at scale.
Source: Peptide Therapeutics Market Reports (2023), Evaluate Pharma.
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Largest-scale peptide manufacturing
Lipidated peptide analogues
Tonne scale
~30-residue analogues with a C18 fatty diacid chain
Attaching a fatty diacid to a lysine side chain lets a peptide bind reversibly to serum albumin, extending its half-life from minutes to about a week. That single piece of chemistry turned ~30-residue peptides into products made by solid-phase synthesis on a tonne scale — a volume nobody expected peptide manufacturing to reach.
tonnes
annual production scale
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Longest natural peptide / shortest protein
Adrenomedullin (52 aa)
52 aa
MW ~6 kDa · Adrenal medulla · Vasodilatory hormone
The peptide/protein boundary is conventionally ~50 amino acids (arbitrary). Adrenomedullin at 52 residues sits right at the edge. Among classic peptide hormones, CRH (41 aa) and NPY (36 aa) also push the upper limit. The longest spider silk spidroin, at ~4,000 residues, is unambiguously a protein.
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Most abundant peptide in the human body
Glutathione
5–10 mM
ECG (Glu-Cys-Gly) · MW 307 Da · All living cells
Glutathione (γ-Glu-Cys-Gly) is present in virtually every cell at 5–10 mM — the most abundant small peptide in human biology and the body's primary antioxidant. Red blood cells contain ~2 mM to protect hemoglobin. Without it, cells would be destroyed by their own metabolic byproducts.
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First medicine from a cone snail peptide
Ziconotide (from ω-MVIIA)
2004
Binds N-type calcium channels · 25 aa · Conus magus
ω-Conotoxin MVIIA blocks N-type calcium channels, a mechanism unrelated to opioid receptors. It physically blocks the channels in spinal cord neurons, preventing pain signals from reaching the brain. Its target is a calcium channel, not an opioid receptor, so its pharmacology is entirely different.
Source: Miljanich GP. (2004) Ziconotide: neuronal calcium channel blocker. Curr Med Chem.
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First peptide ever synthesized
Glycylglycine (Gly-Gly)
1901
GG · MW 132 Da · Emil Fischer · Berlin
In 1901, Emil Fischer linked two glycines with what he named the peptide bond — producing the world's first synthetic peptide. He coined 'peptide' from Greek peptos (digested). This single experiment is the founding moment of all peptide chemistry and the modern drug industry.
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Most pharmacologically diverse venom
Cone Snail Venom
100–200
Distinct conopeptides per species · 700 species · ~140,000 total
Each of the ~700 cone snail species produces 100–200 pharmacologically distinct conopeptides. Combined: up to 140,000 unique bioactive peptides — the planet's most diverse peptide pharmacopeia. Less than 1% have been characterized in the lab.
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Smallest known neurotoxic peptide
Apamin
18 aa
CNCKAPETALCARRCQQH · MW 2,027 Da · Honey bee venom
Apamin, from honeybee venom, is the smallest naturally occurring neurotoxic peptide. Just 18 residues — stabilised by two disulfide bonds — it crosses the blood-brain barrier and specifically blocks SK potassium channels in neurons that regulate memory formation. Its extraordinary selectivity has made it one of the most important pharmacological tools in neuroscience for dissecting cognition circuits.
Source: Habermann E. (1972) Bee and wasp venoms. Science 177(4046):314-22.
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Most stable natural peptide
Kalata B1
Indestructible
GLPVCGETCVGGTCNTPGCTCSWPVCTRN · 29 aa · Viola odorata
Kalata B1 from sweet violet is the most chemically stable natural peptide known. Its head-to-tail cyclic backbone plus three interlocking disulfide bonds (a cystine knot) make it impervious to boiling, acid, base, and all known proteases. Originally found in an African medicinal tea used to accelerate childbirth, the cyclotide scaffold is now used in drug design to graft active sequences into an indestructible molecular framework.
Source: Craik DJ et al. (1999) The cyclotide family of circular miniproteins. J Mol Biol.