Mastoparan
A 14-amino-acid wasp-venom peptide that switches on G proteins, triggers mast cells, and punches holes in membranes — a classic lab tool, not a drug
Mastoparan is a short peptide — fourteen amino acids, Ile-Asn-Leu-Lys-Ala-Leu-Ala-Ala-Leu-Ala-Lys-Lys-Ile-Leu-NH2 — from the venom of the wasp Vespula lewisii, first described in 1979 as a 'mast-cell degranulating' peptide: it makes mast cells dump their histamine, part of why wasp stings sting. Its real fame in the lab came later, when it was shown to do something unusual — activate the cell's heterotrimeric G proteins directly, from the inside, mimicking the signal a hormone receptor normally sends. That made mastoparan a go-to tool for studying G-protein signalling. Chemically it is an amphipathic, positively charged helix: one face greasy, one face charged, which lets it insert into and disrupt membranes. That membrane activity makes mastoparan and its many engineered variants (mastoparan-L, -M, -X, Polybia-MP-I) antimicrobial, antiviral and toxic to tumour cells, which is where much current research sits. Mastoparan is a venom peptide and research tool; it is not an approved medicine and has not been given to people as a treatment.
No established human dose Details ↓
Recommended Dosing
No established human dose
Mastoparan is a wasp-venom peptide and research tool; it has never been given to people as a treatment. The work is in cells and animals, where synthetic peptide or its analogs are used at experimental amounts that do not carry over to people.
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What is it?
Mastoparan is the prototype of a family of wasp-venom peptides. It was isolated from the venom of the wasp Vespula lewisii and named in 1979 for its most obvious effect: degranulating mast cells, the immune cells that release histamine, which contributes to the local reaction to a wasp sting. Structurally it is a 14-residue, positively charged, amphipathic peptide that folds into an alpha-helix with a hydrophobic face and a cationic face — the classic architecture of a membrane-active peptide.
Its defining laboratory property, shown by Higashijima and colleagues in 1988, is direct activation of heterotrimeric G proteins. Mastoparan speeds up GTP binding and GTPase activity of purified G proteins by promoting the release of bound GDP — exactly the mechanism a cell-surface receptor uses — and pertussis toxin blocks this, just as it uncouples receptors from G proteins. In a lipid membrane, mastoparan adopts a shape resembling the cationic intracellular loop of a G-protein-coupled receptor, so it mimics an agonist-bound receptor from the inside. This made mastoparan a standard pharmacological tool for probing G-protein signalling.
The same amphipathic helix that lets mastoparan sit in membranes also lets it permeabilise them, and much modern work exploits that. A systematic study of 55 natural mastoparan-family peptides from wasp venoms sorted them into subfamilies and showed most trigger mast-cell degranulation, with the hydrophobic face and C-terminal amidation being critical — a structure-function map for the family. Engineered mastoparan derivatives have been designed as antibacterial agents: a tryptophan-substituted, rearranged analog killed multidrug-resistant bacteria by disrupting their membranes and treated infection in mice with low toxicity.
Mastoparan's membrane activity extends to viruses and tumours. Mastoparan-L-derived peptides inhibited herpes simplex virus 1 in cell culture, largely by disrupting the viral particle before it attached to cells. And mastoparan-M, delivered in a phytosome nanoparticle, suppressed breast-cancer growth in mice by disturbing mitochondrial membrane integrity and triggering apoptosis; a related wasp peptide, Polybia-mastoparan I, packaged in bacterial outer-membrane vesicles, restricted bladder-cancer growth in mice while stimulating anti-tumour immunity. These illustrate why mastoparans are studied as antimicrobial and anticancer leads and as cell-penetrating/delivery peptides.
Throughout, mastoparan is a venom peptide and a research tool. No published study has given mastoparan to people as a treatment, it is approved nowhere, and material sold online under its name is an unregulated research chemical — one whose mast-cell-degranulating, membrane-lytic nature makes it biologically potent. Nothing here is a dose or a therapy; this page records what the published science says.
Mechanism of Action
Mastoparan is an amphipathic, cationic wasp-venom alpha-helix with two linked modes of action: it activates heterotrimeric G proteins directly (mimicking a receptor) and degranulates mast cells, and it inserts into and disrupts membranes, giving it antimicrobial, antiviral and anticancer activity.
Direct G-protein activation
Promotes GDP release and GTP binding on heterotrimeric G proteins, mimicking an agonist-bound GPCR; pertussis-toxin-sensitive (PMID 3129426).
Mast-cell degranulation
Triggers histamine release from mast cells — its original named activity — shared across the wasp mastoparan family (PMIDs 540362, 37235365).
Membrane disruption
As an amphipathic cationic helix it permeabilises microbial, viral and tumour-cell membranes, underlying its antimicrobial, antiviral and anticancer effects (PMIDs 40248899, 38932240, 39816377).
Published Research
These are studies of mastoparan read from their PubMed records on November 7, 2026: the 1979 discovery of the mast-cell-degranulating wasp-venom peptide; the 1988 demonstration that it activates G proteins directly; a structure-function survey of the mastoparan family's degranulation activity; and studies of mastoparan-derived antibacterial, antiviral and anticancer peptides in cells and animals. The evidence is in cells and animals; mastoparan has not been given to people as a treatment.
Discovery: mastoparan, a mast-cell-degranulating wasp-venom peptide
A new peptide was isolated from the venom of the wasp Vespula lewisii, its amino-acid sequence determined, and it was named mastoparan for its ability to degranulate mast cells — the founding description of the mastoparan family of wasp-venom peptides (a discovery study).
Mastoparan activates G proteins directly, mimicking a receptor
Mastoparan increased the GTPase activity and nucleotide binding of purified heterotrimeric G proteins by promoting release of bound GDP — the same mechanism cell-surface receptors use — and pertussis toxin blocked this; in a lipid bilayer its structure resembled the cationic intracellular loop of a G-protein-coupled receptor, so it mimics an agonist-bound receptor from the inside (the classic mechanistic study).
Diversity and mast-cell degranulation of the mastoparan family
A systematic survey of 55 natural mastoparan-family peptides from wasp venoms sorted them into four subfamilies and, via a synthetic peptide library tested on mast-cell lines, found most induced mast-cell degranulation; the hydrophobic face and C-terminal amidation were critical for activity — a structure-function map of the family (an in-vitro study).
Mastoparan-derived antibacterial peptides against drug-resistant bacteria (mice)
Peptides engineered from a mastoparan (tryptophan substitution and residue rearrangement) included an analog with high activity against multidrug-resistant bacteria and low cytotoxicity and hemolysis; it killed bacteria mainly by membrane disruption and treated infection in mice — a preclinical antibacterial result built on the mastoparan scaffold.
Mastoparan-L-derived peptides inhibit herpes simplex virus 1
Mastoparan-L-derived peptides inhibited HSV-1 in Vero cells, with over 80% inhibition and up to 99% suppression of viral replication, acting mainly at the early infection stage; an alpha-helical analog appeared to disrupt the viral particle before cell attachment — an antiviral mechanism (an in-vitro study).
Mastoparan-M nanoparticles suppress breast cancer in mice
Mastoparan-M, delivered in a phytosome nanoparticle, inhibited breast-cancer (4T1) cell growth by arresting the cell cycle and disrupting mitochondrial membrane integrity, accumulated at tumours and suppressed tumour growth in a mouse model with favorable tolerability — a preclinical anticancer result for the mastoparan scaffold.
No Established Human Dose
Mastoparan is a wasp-venom peptide and research tool; it has never been given to people as a treatment. The work is in cells and animals, where synthetic peptide or its analogs are used at experimental amounts that do not carry over to people. No regulator has approved any dose, and no published human dose exists, so no amount is printed here.
What this rests on: PMID 540362, PMID 3129426, PMID 40248899.
Educational information, not medical advice. The doses on this page come from approved labels, published studies and, where no study exists, amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no label and no published test that says what forms or vial sizes Mastoparan is sold in. A vial's own label is a seller's claim, not a source.
Mixing a vial: a worked example
Unknown: no human dose of Mastoparan has been established (see No Established Human Dose below), so there is no amount to work out. The reconstitution calculator does the arithmetic for any vial, water and dose.
Storage before and after mixing
Unknown: no label or published stability study on file says how to store Mastoparan, before or after mixing. The mixing guide sets out the general rules, with their sources: keep a mixed vial in the fridge, and use it promptly, as the bacteriostatic water label says of any drug dissolved in it. The 28 days often quoted is the limit for an opened multiple-dose vial from a manufacturer, an outer limit set for sterility, not a time a mixed solution has been shown to keep. Nobody has published how long Mastoparan stays intact once mixed.
How it is taken
Unknown: with no established human dose, there is no established way of taking Mastoparan. What the human studies gave and how is set out under No Established Human Dose.
What to expect, and when
How long it stays in the body: a half-life of not established for humans; a membrane-active venom peptide used as a research tool. After about five half-lives almost none is left.
When effects appear: unknown; no source on this page gives a time to effect for Mastoparan. Results reported in the studies are under Published Research.
Source: half-life: PMID 39816377.
Side effects, and when to stop or get help
From the Side Effects section: No human adverse-event data exist: no published study has administered mastoparan to people as a treatment; It is a mast-cell degranulator (histamine release) and a membrane-lytic peptide, so allergic-type and cell-damaging effects are intrinsic to its action — a biological fact, not a safety profile; Some mastoparan analogs can be hemolytic/cytotoxic; engineering (e.g. tryptophan substitution) is used to reduce this (PMID 40248899) — a design consideration, not human data; Material sold online as 'mastoparan' is an unregulated research chemical of unverified content and potent biological activity. Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping Mastoparan. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“Mastoparan is a venom peptide that has not been given to people as a drug, so there is no human safety profile; the points below reflect that research status and its potent biology”).
Interactions
Unknown: a PubMed search for human interaction studies of Mastoparan (reviewed 2026-11-07) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of Mastoparan products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: Research Chemical (Not a drug: Drugs@FDA and the openFDA label endpoint hold no record, and FDA GSRS and ChEMBL hold no approved-drug record for mastoparan (searched November 7, 2026)). Sport: Not on the 2026 List.
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
Mastoparan is a venom peptide that has not been given to people as a drug, so there is no human safety profile; the points below reflect that research status and its potent biology.
Contraindications & Cautions
Mastoparan has no approved use and no label. These points reflect its research status.
Legal Status
Mastoparan is a wasp-venom peptide used as a research compound; it is not a drug and is not approved in any country.
Frequently Asked Questions
?What is mastoparan?
A 14-amino-acid amphipathic peptide (Ile-Asn-Leu-Lys-Ala-Leu-Ala-Ala-Leu-Ala-Lys-Lys-Ile-Leu-NH2) from the venom of the wasp Vespula lewisii, first described in 1979 as a mast-cell-degranulating peptide (PMID 540362).
?Why is it used in the lab?
Because it activates the cell's heterotrimeric G proteins directly, mimicking a hormone receptor — a handy tool for studying G-protein signalling (PMID 3129426).
?What is it being studied for?
As an amphipathic membrane-active peptide, mastoparan and its variants are studied as antibacterial, antiviral and anticancer agents in cells and animals (PMIDs 40248899, 38932240, 39816377).
?Is it a drug I can take?
No. Mastoparan is not a medicine, has no FDA application or label, and is approved nowhere. It is a biologically potent venom peptide; material sold online as mastoparan is an unregulated research chemical. Grey Peptides lists no sellers and recommends no source.
References
- [mechanism] Hirai Y, et al. "A new mast cell degranulating peptide "mastoparan" in the venom of Vespula lewisii." Chem Pharm Bull (Tokyo), 1979;27(8):1942-4. PMID: 540362.
- [mechanism] Higashijima T, et al. "Mastoparan, a peptide toxin from wasp venom, mimics receptors by activating GTP-binding regulatory proteins (G proteins)." J Biol Chem, 1988;263(14):6491-4. PMID: 3129426.
- [mechanism] Ye X, et al. "Characterization of the Molecular Diversity and Degranulation Activity of Mastoparan Family Peptides from Wasp Venoms." Toxins (Basel), 2023;15(5). PMID: 37235365.
- [animal] Jing J, et al. "The α-Helical Antibacterial Peptides Derived from Mastoparan with Broad-Spectrum Activity against Multidrug-Resistant Pathogens." ACS Infect Dis, 2025;11(5):1129-1139. PMID: 40248899.
- [mechanism] Vilas Boas LCP, et al. "Antiviral Activities of Mastoparan-L-Derived Peptides against Human Alphaherpesvirus 1." Viruses, 2024;16(6). PMID: 38932240.
- [animal] Zhao H, et al. "Phytosomes Loaded with Mastoparan-M Represent a Novel Strategy for Breast Cancer Treatment." Int J Nanomedicine, 2025;20:109-124. PMID: 39816377.
- [other] Mastoparan is a tetradecapeptide (Ile-Asn-Leu-Lys-Ala-Leu-Ala-Ala-Leu-Ala-Lys-Lys-Ile-Leu-NH2) isolated from the venom of the wasp Vespula lewisii and named by Hirai and colleagues in 1979 as a mast-cell-degranulating peptide, as described in the discovery paper carded on this page (read November 7, 2026). Many natural and engineered variants exist (mastoparan-L, -M, -X, Polybia-MP-I).
- [other] US FDA, Drugs@FDA and the openFDA label endpoint, searched November 7, 2026: no application and no label record for mastoparan. It is a wasp-venom peptide used as a research tool and studied as an antimicrobial/anticancer lead, not a drug; FDA GSRS and ChEMBL hold no approved-drug record for it.
Sources & Citations
The six studies carded above were read from their PubMed records on November 7, 2026. Mastoparan's sequence, its origin from Vespula lewisii venom, its mast-cell-degranulating activity, its direct activation of G proteins, the family's structure-function map, and the antibacterial, antiviral and anticancer activity of mastoparan-derived peptides are from the discovery paper and studies carded here; the absence of US approval or a drug record from Drugs@FDA, openFDA, FDA GSRS and ChEMBL was checked the same day. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.