Compound monograph
Met-enkephalin
Met-enkephalin is a linear five-residue peptide with the sequence Tyr-Gly-Gly-Phe-Met and free amino and carboxyl termini.
01
Identity & nomenclature
Met-enkephalin is a linear five-residue peptide with the sequence Tyr-Gly-Gly-Phe-Met and free amino and carboxyl termini.
Metenkefalin is the WHO Recommended INN List 59 name for this parent. A D-tyrosyl synonym collected by PubChem conflicts with its specified structure and is excluded. PubMed and Nature give different ending pages for Hughes et al.; that pagination discrepancy remains unresolved.
Canonical name: Metenkefalin.
Declared aliases and development codes: Methionine enkephalin, Methionine-enkephalin, [Met5]enkephalin.
02
Molecular properties
| Molecular formula | C27H35N5O7S |
|---|---|
| Molecular mass | 573.665 Da |
| CAS Registry Number | 58569-55-4 |
| PubChem CID | 443363 |
| UNII | 9JEZ9OD3AS |
| One-letter sequence | YGGFM |
| Three-letter sequence | Tyr–Gly–Gly–Phe–Met |
| Terminal groups | Free N-terminus; Free C-terminal carboxyl |
Positions count the mature chain from 1. All chiral amino-acid residues are L; glycine is achiral. Terminal groups are recorded separately.
03
Structural characteristics
The chain contains standard L-amino-acid residues and no inter-residue covalent closure.
Terminal features: Free N-terminus, Free C-terminal carboxyl.
04
Molecular targets & mechanisms
05
Analytical considerations
The molecular formula describes the parent; the average mass is calculated using CIAAW 2024 abridged atomic weights. PubChem reports 573.7 Da at one-decimal precision: the calculated minus displayed difference is -0.035 Da (-61.0075 ppm), consistent with that display precision. Hydrated crystal associations do not add covalent peptide rings.
What the studies reported
No verified findings are published for this record under Content Policy v1.
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Verified bibliography
Cited studies by type
The 4 papers this record cites, counted by the kind of work each reports. A count is the size of this record's selection, not of the research that exists, and says nothing about results, safety, effectiveness or approval.
A paper can report more than one kind of work. Each count opens those papers in the bibliography. Compare every record on the Evidence Map.
Reference 1
Identification of two related pentapeptides from the brain with potent opiate agonist activity.Hughes J, Smith TW, Kosterlitz HW, Fothergill LA, Morgan BA, Morris HR
Nature · 1975-12-18 · Journal Article
currentReference 2
Morphine-like peptides in mammalian brain: isolation, structure elucidation, and interactions with the opiate receptor.Simantov R, Snyder SH
Proceedings of the National Academy of Sciences of the United States of America · 1976-07 · Journal Article
currentReference 3
Preliminary analysis of 1H and 13C spectral and relaxation behavior in methionine-enkephalin.Bleich HE, Cutnell JD, Day AR, Freer RJ, Glasel JA, McKelvy JF
Proceedings of the National Academy of Sciences of the United States of America · 1976-08 · Journal Article
currentReference 4
The crystal structures of [Met5]enkephalin and a third form of [Leu5]enkephalin: observations of a novel pleated beta-sheet.Griffin JF, Langs DA, Smith GD, Blundell TL, Tickle IJ, Bedarkar S
Proceedings of the National Academy of Sciences of the United States of America · 1986-05 · Journal Article
current
Study models of these references
What kind of experiment each cited paper reports, taken from its abstract unless marked. Not a summary of results.
| Reference | Study models |
|---|---|
| Hughes J et al. 1975 | Chemical, structural or analytical study; no biological model reported |
| Simantov R et al. 1976 | Study models reported: in vitro · from the abstract |
| Bleich HE et al. 1976 | Chemical, structural or analytical study; no biological model reported |
| Griffin JF et al. 1986 | Chemical, structural or analytical study; no biological model reported |
Record history
Published 2026-10-21.
- : Analytical notes
Each entry names the parts of this record that changed on that date. Changes to links between records and to catalogue links are not listed. This history covers the tracked record fields; study findings are not listed here.
Cite this record: Purely Peptides Research Library. Met-enkephalin. Published 2026-10-21; updated 2026-10-21. https://purelypeptides.org/research/compounds/met-enkephalin/
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Methodology & citation verification
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