Page data last changed: . Chemistry registry snapshot: . Registry refreshes and identity assessments are separate from scientific content review.
Pentapeptide opioid — YGGF is the classic motif.
Part of the Neuropeptides & signaling cluster
Overview
Met-enkephalin (YGGFM) is an endogenous opioid pentapeptide foundational to pain and reward neurobiology research.
Source & context
Biological / chemical source: Brain, adrenal
Primary research or clinical context: Pain & reward research
Opioid peptide family
Enkephalins, endorphins, and dynorphins share related motifs and receptor preferences — a core chapter in neuropeptide education.
Sequence
One-letter sequence commonly cited for Met-enkephalin (educational; isoforms and modifications may differ):
YGGFM
Residues plotted ~100° apart around an α-helix — clustering of one color reveals an amphipathic face.
Structure & chemistry
Molecular identity & reference confidence
Source-supported reference
Reference values are taken from the cited molecular record or curated profile. A database match is not independent laboratory verification; modifications, counter-ions, and formulations can change the measured mass.
- Molecular form
- Met-enkephalin (source record; form not independently established)
- Species
- Not established by this molecular identity audit
- Termini (N / C)
- Not specified / Not specified
Average reference mass
Reference policy updated: 2026-10-05
- PubChem molecular record · 2026-10-01
- Molecular formula
- C27H35N5O7S
- Average reference mass
- ≈ 573.7
- PubChem CID: 443363
- CAS RN: 58569-55-4
- UNII: 9JEZ9OD3AS
Chemistry values: PubChem · fetched 2026-10-01.
Clinical development snapshot
ClinicalTrials.gov lists 8 registered studies with “Met-enkephalin” as an intervention (snapshot 2026-10-01). A registry footprint is not evidence of efficacy or approval.
| NCT | Title | Phase | Status | Updated |
|---|---|---|---|---|
| NCT03283397 | A Phase IIIb, Multicenter, International Study to Evaluate the Efficacy, Safety and Tolerability of EK-12 in P | Phase 3 | terminated | 2024-08-13 |
| NCT04374032 | Clinical Trial to Evaluate the Efficacy and Safety of an Immunomodulatory Therapy for the Treatment of Patient | Phase 3 | completed | 2020-12-24 |
| NCT00109941 | Opioid Growth Factor in Treating Patients With Advanced Pancreatic Cancer That Cannot Be Removed By Surgery | Phase 2 | completed | 2018-09-06 |
| NCT00783172 | Opioid Growth Factor (OGF) and Gemcitabine: Novel Treatment for Pancreatic Cancer | Phase 1 | terminated | 2018-09-06 |
| NCT00706576 | Treatment of Unresectable Hepatocellular Cancer With Opioid Growth Factor | Phase 1 | completed | 2017-08-02 |
| NCT00982696 | Treatment of Advanced Head and Neck Cancer | Phase 2 | terminated | 2014-09-30 |
Met-enkephalin — 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: Met-enkephalin (source record; form not independently established)Average reference mass: 573.7 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 Met-enkephalin
What is Met-enkephalin?+
Met-enkephalin (YGGFM) is an endogenous opioid pentapeptide foundational to pain and reward neurobiology research.
What Canadian product status is recorded for Met-enkephalin?+
Canadian product status for Met-enkephalin 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 typical length of Met-enkephalin?+
Met-enkephalin is commonly described as approximately 5 amino acids (Neuropeptide).
Related peptides
References & further reading
- 1.Clement-Jones et al. (1980). Met-enkephalin circulates in human plasma. Nature
- 2.Fischer et al. (1987). Interaction of met-enkephalin with human granulocytes. Ann N Y Acad Sci
- 3.Szweda et al. (2016). Smart Polymeric Nanocarriers of Met-enkephalin. Biomacromolecules
- 4.Scanes et al. (2024). Disparate Effects of Stressors on Met-Enkephalin System Parameters and on Plasma Concentrations of Corticosterone in Young Female Chickens. Animals (Basel)
- 5.Eybalin et al. (1984). Immunofluorescence with Met-enkephalin and Leu-enkephalin antibodies in the guinea pig cochlea. Hear Res
- 6.Nabeshima et al. (1992). Stress-induced changes in brain Met-enkephalin, Leu-enkephalin and dynorphin concentrations. Life Sci
- 7.Pierzchała-Koziec et al. (2019). Isolation stress impacts Met-enkephalin in the hypothalamo-pituitary-adrenocortical axis in growing Polish Mountain sheep: a possible role of the opioids in modulation of HPA axis. Stress
- 8.Kamel et al. (2007). Plasma met-enkephalin, beta-endorphin and leu-enkephalin levels in human hepatic encephalopathy. East Mediterr Health J
- 9.PubChem — compound summary for Met-enkephalin (CID 443363)
- 10.Wikipedia — Met-enkephalin