Compound monograph
Spexin
Spexin is an endogenous fourteen-residue amidated neuropeptide identified by computational screening of the human proteome, and a ligand of galanin receptors 2 and 3.
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Identity & nomenclature
Spexin is an endogenous fourteen-residue amidated neuropeptide identified by computational screening of the human proteome, and a ligand of galanin receptors 2 and 3.
Spexin and spadin are unrelated peptides. Mature spexin has fourteen residues, and PE 22-28 is derived from the sortilin propeptide. The former alias Spexin (22-28) incorrectly assigned that fragment to spexin. NPQ is a discovery-era designation that may refer to the precursor; it does not by itself identify the mature amidated peptide.
Declared aliases and development codes: SPX, Spexin-1, NPQ.
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Molecular properties
| Molecular formula | C74H114N20O19S |
|---|---|
| Molecular mass | 1619.9 Da |
| CAS Registry Number | 1370290-58-6 |
| PubChem CID | 122705996 |
| One-letter sequence | NWTPQAMLYLKGAQ |
| Three-letter sequence | Asn–Trp–Thr–Pro–Gln–Ala–Met–Leu–Tyr–Leu–Lys–Gly–Ala–Gln |
| Terminal groups | Free N-terminus; C-terminal amide |
Fourteen residues with a C-terminal amide, free N-terminus and no disulfide, lactam or lipid conjugation.
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Structural characteristics
A hidden Markov model screen identified the spexin precursor, followed by secretory-granule localization and recovery from cell supernatant. These observations concern precursor expression and secretion; they do not alone identify intact mature spexin. Ligand-receptor experiments found spexin activation of GALR2 and GALR3, with no GALR1 activation in the reported panel and greater potency at GALR3 than the galanin comparator. A cryo-EM study determined a spexin-bound GALR2-Gq complex. Evolutionary analysis supports local duplication of spexin, galanin and kisspeptin genes before two rounds of vertebrate whole-genome duplication.
Terminal features: Free N-terminus, C-terminal amide.
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Molecular targets & mechanisms
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Analytical considerations
Confirmation needs the fourteen-residue sequence and the terminal amide together; the free acid is 0.98 Da heavier than the amide and deamidation must be localised rather than inferred from intact mass. Include a methionine-oxidation assessment. Precursor-derived intermediates extended at the N-terminus or carrying the amidation-donor glycine should be looked for explicitly, since detecting precursor expression or immunoreactivity does not establish that the mature amidated peptide is present.
Disagreements and mix-ups
Points where sources disagree about this compound's identity, or where a name or form is easily confused with another, as noted in this record. The discrepancy register quotes the passage for each one.
Often mixed up · Name or substance
PE 22-28 is not a fragment of spexinAlso noted in PE 22-28
Often mixed up · Name or substance
NPQ: precursor or mature spexin
What the studies reported
Each finding describes one cited study in its stated model. These observations are specific to that study and do not establish effects in other settings.
Cell and tissue studies
Human, Xenopus and zebrafish GALR2/3 ligand-receptor activation assays
Using human, Xenopus and zebrafish GALR2/3 ligand-receptor activation assays, the study observed receptor activation by SPXs.
Reference [2]GALR1 ligand-receptor activation assay
Using a GALR1 ligand-receptor activation assay, the study observed no receptor activation by SPXs.
Reference [2]Human GALR2-mini-Gq cryo-electron microscopy preparation
Using a human GALR2-mini-Gq cryo-electron microscopy preparation, the study reported a spexin-bound complex at 3.5 Å nominal resolution.
Reference [3]
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Verified bibliography
Cited studies by type
The 3 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 novel peptide hormones in the human proteome by hidden Markov model screening.Mirabeau O, Perlas E, Severini C, Audero E, Gascuel O, Possenti R, Birney E, Rosenthal N, Gross C
Genome research · 2007-02-06 · Journal Article
currentReference 2
Coevolution of the spexin/galanin/kisspeptin family: Spexin activates galanin receptor type II and III.Kim DK, Yun S, Son GH, Hwang JI, Park CR, Kim JI, Kim K, Vaudry H, Seong JY
Endocrinology · 2014-02-11 · Journal Article
currentReference 3
Structural insights into galanin receptor signaling.Jiang W, Zheng S
Proceedings of the National Academy of Sciences of the United States of America · 2022-05-20 · 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 |
|---|---|
| Mirabeau O et al. 2007 | Study models reported: in vitro · from the abstract |
| Kim DK et al. 2014 | Study models reported: in vitro · from the abstract |
| Jiang W et al. 2022 | Study models reported: in vitro · from the abstract |
Record history
Published 2026-09-19.
- : Sequence and structure
- : Sequence and structure
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. Spexin. Published 2026-09-19; updated 2026-10-15. https://purelypeptides.org/research/compounds/spexin/
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Methodology & citation verification
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