Which kisspeptin does a vial labelled "kisspeptin" contain?

The label alone does not say. UniProt lists four forms cut from the same precursor: kisspeptin-54 (metastin), -14, -13 and -10. They share the last ten residues but differ in length and mass, so LC-MS tells them apart easily, and a mixture shows as separate masses in one run. Tell the partner laboratory which form you expect before testing.

What mass should a kisspeptin-10 certificate show?

PubChem lists kisspeptin-10 at an average molecular weight of 1302.4 g/mol and a monoisotopic mass of 1301.63 Da, with an amidated C-terminus. A main mass near 5857 g/mol instead indicates kisspeptin-54. A mass about 1 Da high can mean deamidation or a free-acid C-terminus, which needs high-resolution mass spectrometry to confirm.

Does kisspeptin-10 degrade in the vial?

It can. A 2024 anti-doping study found a degradation product probably caused by oxidation of its tryptophan to kynurenine, and a black-market vial it examined appeared more degraded than the reference standard, though it held no unexpected impurities. A quantified, degradation-aware test shows how much intact kisspeptin-10 remains, which is the figure to compare with the label.

One of the 30 compound testing profiles

Kisspeptin

Kisspeptin-10 is a 10-amino-acid amidated peptide (C63H83N17O14, average mass 1302.4 g/mol); because the name kisspeptin also covers the 54-residue form, a test should first confirm which length the vial holds, then look for oxidation of its single tryptophan.

Kisspeptins are C-terminally amidated peptides cut from the human KiSS-1 precursor, which UniProt lists in four lengths: metastin (kisspeptin-54), kisspeptin-14, kisspeptin-13 and kisspeptin-10, all sharing the same final ten residues (UniProt Q15726).

Test your kisspeptin

Identity card

Formula: C63H83N17O14
Average mass: 1,302.4 g/mol
Monoisotopic mass: 1,301.63 Da
Length: 10 residues
Modifications: C-terminal amide (Phe10-NH2); Free N-terminus
Also sold as: Kisspeptin-10, KP-10, Kisspeptin-54, KP-54, Metastin
Sequence: YNWNSFGLRF
Note: Identity fields describe kisspeptin-10 (PubChem CID 25240297). The name kisspeptin alone is also used for kisspeptin-54, also called metastin (PubChem CID 71306396, C258H401N79O78, average mass 5857 g/mol, monoisotopic mass 5853.98 Da). The PubChem kisspeptin-54 structure has Arg at position 14, which matches a natural variant listed by UniProt (rs4889, precursor position 81); the UniProt reference sequence has Pro there, so a kisspeptin-54 made to that sequence has a different mass. Kisspeptin-13 and kisspeptin-14 are further forms listed in UniProt Q15726.

Source: Kisspeptin-10 compound record (CID 25240297), Kisspeptin (kisspeptin-54) compound record (CID 71306396), Metastasis-suppressor KiSS-1 (Q15726).

Check a certificate's mass against these values with the mass checker, prefilled for Kisspeptin.

What usually goes wrong with kisspeptin. Documented failure modes, with sources.

One name, four molecules

UniProt places metastin (kisspeptin-54) at residues 68 to 121 of the KiSS-1 precursor, kisspeptin-14 at 108 to 121, kisspeptin-13 at 109 to 121 and kisspeptin-10 at 112 to 121, all ending in a phenylalanine amide (UniProt Q15726). PubChem titles its 54-residue record simply "Kisspeptin", at 5857 g/mol (PubChem), against 1302.4 g/mol for kisspeptin-10 (PubChem). Agree the expected form before testing, or a correct result can read as a failure. For kisspeptin-54, also agree the residue at position 14: the PubChem structure carries Arg, the UniProt reference sequence carries Pro.

Tryptophan oxidation to kynurenine

Kisspeptin-10 has one tryptophan, at position 3. An anti-doping study that validated an LC-HRMS method for kisspeptin-10 found a degradation product probably caused by oxidation of that tryptophan to kynurenine, and when it analysed a black-market vial, the product had no unexpected impurities but appeared more degraded than the purchased reference standard (Colpaert et al., 2024). Tryptophan oxidation also occurs easily during sample handling (König et al., 2023), so a small oxidised peak needs the handling history before it is blamed on the product. Oxidised forms differ in mass, so LC-MS shows them where UV purity alone may not.

Two asparagines and a C-terminal amide

Kisspeptin-10 contains Asn2 and Asn4. Asparagine deamidation proceeds through a succinimide intermediate and can produce isoaspartyl residues (Reissner and Aswad, 2003). The C-terminal amide is a further deamidation site: in heat-stressed oxytocin, the C-terminal Gly9 amide deamidated fastest of the three sites, each event adding 0.985 Da, and the products were identified by ESI-MS/MS (Hawe et al., 2009). A shift that small needs accurate mass, and an isoaspartyl product has the same mass as the aspartyl one, so only chromatography separates those two.

Which tests matter most

LC-MSSettles which kisspeptin is present (10, 13, 14 or 54 residues) and separates kynurenine-oxidised forms from intact peptide.
HRMSResolves the 0.985 Da shift of deamidation at Asn2, Asn4 or the C-terminal amide.
HPLC-UVGives purity and separates same-mass isoaspartyl forms and degradation products from the main peak.
Counter-ion contentThe free N-terminus and Arg9 bind counter-ions, so peptide content differs from powder weight.

Reading kisspeptin results

When kisspeptin-10 was incubated in human serum, four breakdown products corresponding to the y9, y8, y7 and y5 fragments were found (Colpaert et al., 2024). Y-type fragments keep the C-terminus, so these are chains missing Tyr1 and progressively more. They were found under biological conditions, but they are also the masses to check if a vial shows lighter, related peaks.

UniProt annotates the tyrosine at precursor position 112, the first residue of kisspeptin-10, as a phosphotyrosine (UniProt Q15726). The PubChem record for synthetic kisspeptin-10 has an ordinary tyrosine there (PubChem). A report that discusses modifications should say which structure it used as its reference.

Public Tested.ph results

No public kisspeptin records yet

Each public kisspeptin record will appear here with its identity, HPLC purity and measured amount against the label, once the first vial is tested.

FIG 13Amount against the label

Questions about testing kisspeptin

Which kisspeptin does a vial labelled "kisspeptin" contain?: The label alone does not say. UniProt lists four forms cut from the same precursor: kisspeptin-54 (metastin), -14, -13 and -10. They share the last ten residues but differ in length and mass, so LC-MS tells them apart easily, and a mixture shows as separate masses in one run. Tell the partner laboratory which form you expect before testing.
What mass should a kisspeptin-10 certificate show?: PubChem lists kisspeptin-10 at an average molecular weight of 1302.4 g/mol and a monoisotopic mass of 1301.63 Da, with an amidated C-terminus. A main mass near 5857 g/mol instead indicates kisspeptin-54. A mass about 1 Da high can mean deamidation or a free-acid C-terminus, which needs high-resolution mass spectrometry to confirm.
Does kisspeptin-10 degrade in the vial?: It can. A 2024 anti-doping study found a degradation product probably caused by oxidation of its tryptophan to kynurenine, and a black-market vial it examined appeared more degraded than the reference standard, though it held no unexpected impurities. A quantified, degradation-aware test shows how much intact kisspeptin-10 remains, which is the figure to compare with the label.

Sources

Kisspeptin-10 compound record (CID 25240297), PubChem, US National Library of Medicine
Kisspeptin (kisspeptin-54) compound record (CID 71306396), PubChem, US National Library of Medicine
Metastasis-suppressor KiSS-1 (Q15726), UniProt
Colpaert T et al. Investigating the detection of the novel doping-relevant peptide kisspeptin-10 in urine using liquid chromatography high-resolution mass spectrometry. Biomed Chromatogr. 2024;38(9):e5946, Biomedical Chromatography (PubMed)
König S et al. Oxidation products of tryptophan and proline in adipokinetic hormones: artifacts or post-translational modifications? Life (Basel). 2023;13(12):2315, Life (PubMed)
Reissner KJ, Aswad DW. Deamidation and isoaspartate formation in proteins: unwanted alterations or surreptitious signals? Cell Mol Life Sci. 2003;60(7):1281-95, Cellular and Molecular Life Sciences (PubMed)
Hawe A et al. Towards heat-stable oxytocin formulations: analysis of degradation kinetics and identification of degradation products. Pharm Res. 2009;26(7):1679-88, Pharmaceutical Research (PMC)

Last reviewed 6 Oct 2026.