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Most toxic natural peptide
α-Amanitin
7 mg
Bicyclic octapeptide · MW 919 Da · Amanita phalloides
Just 7 milligrams — less than one mushroom cap — is lethal to an adult. 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 & Semaglutide
$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. Synthesis costs exceed $100,000/g. Semaglutide's fatty acid conjugation and purification steps make it one of the most expensive APIs ever manufactured at scale. Global peptide drug market: $50B+ annually.
Source: Peptide Therapeutics Market Reports (2023), Evaluate Pharma.
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Best-selling peptide drug (2024)
Semaglutide (Ozempic / Wegovy)
$21 billion
31-residue GLP-1 analog with C18 fatty diacid chain · Novo Nordisk
Semaglutide is the best-selling drug in the world by revenue. It achieves 15–20% body weight loss — comparable to bariatric surgery. Demand so outstripped manufacturing capacity that Novo Nordisk acquired an entire pharmaceutical factory in North Carolina for $11 billion just to increase supply. A single 31-residue peptide is reshaping global healthcare.
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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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Most potent natural peptide painkiller
Ziconotide (from ω-MVIIA)
1,000×
More potent than morphine · 25 aa · Conus magus
ω-Conotoxin MVIIA is ~1,000× more potent than morphine for neuropathic pain. It physically blocks N-type calcium channels in spinal cord neurons, preventing pain signals from reaching the brain. Unlike opioids: non-addictive, no respiratory depression.
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.