Kisspeptin

Kisspeptin-10 is a C-terminally amidated decapeptide belonging to the RFamide family — a group of neuropeptides defined by their shared arginine-phenylalanine-amide C-terminal motif. That motif is not incidental: it is the recognition element, and its integrity is what a specification for this peptide most needs to establish.

Identity and classification

The KISS1 gene product is processed into peptides of several lengths — 54, 14, 13 and 10 residues — which share the same C-terminal decapeptide. Kisspeptin-10 is that shared core, corresponding to residues 45–54 of the precursor. It is catalogued as an agonist ligand at KISS1R, also designated GPR54.

The older literature name metastin refers to the same gene product and still appears in catalogues.

Species variants — check which one you have

Kisspeptin-10 sequences differ between species at the C-terminal residue, and this is a genuine source of confusion:

• Human: YNWNSFGLRF-NH₂ — terminates in phenylalanine.
• Mouse and rat: the corresponding peptide terminates in tyrosine rather than phenylalanine, making it formally an RYamide rather than an RFamide. Different sequence, different formula, different registry number, different mass.

This listing is the human sequence. A certificate quoting the human CAS alongside a rodent sequence, or vice versa, has conflated the two. Given that the difference is one oxygen atom — 16 Da — it is also not something a low-resolution mass measurement will resolve confidently.

Structure

Ten standard L-residues, C-terminally amidated: Tyr-Asn-Trp-Asn-Ser-Phe-Gly-Leu-Arg-Phe-NH₂. Linear, no cyclisation, no cysteine and no disulfide, no non-natural residues.

Three compositional features shape the analysis:

• The C-terminal RF-amide. Arg-Phe-NH₂ is the family-defining motif. Loss of the amide gives the free acid, which is a different compound.
• One tryptophan at position 3 — the most photolabile standard residue.
• Two asparagines at positions 2 and 4 — and asparagine is the residue most prone to deamidation.

Specification and characterisation

• Deamidation is the characteristic degradation route for this peptide. Asn residues deamidate to aspartate through a succinimide intermediate, giving a +1 Da mass shift and, importantly, a change in charge. With two asparagines there are two such sites. Asn-Gly and Asn-Ser sequences are the fastest deamidating contexts, and this peptide has Asn-Ser at positions 4–5. Ion-exchange chromatography separates deamidated from intact material better than reverse phase does, because the change is one of charge.
• C-terminal amidation completeness. Also a +1 Da difference — which means it is not separable from deamidation by nominal mass alone. High-resolution MS, or peptide mapping, is needed to distinguish the two +1 Da routes.
• RP-HPLC purity at 214 nm, with 280 nm strongly informative via the tryptophan and tyrosine.
• Tryptophan oxidation to N-formylkynurenine on light exposure, a +32 Da change.
• Counter-ion and net peptide content. Commonly supplied as the acetate or trifluoroacetate.

Handling and stability

Store sealed at 2–8 °C, desiccated, protected from light. Light protection is specific here, driven by the tryptophan.

Reference catalogues do not recommend storing aqueous solutions of this peptide beyond one day. Deamidation is base-catalysed and accelerates markedly above neutral pH, so alkaline buffers are particularly unsuitable for anything but immediate use.

Equilibrate in a desiccator before opening.

Related compounds in this library

No other RFamide peptide is supplied here. PT-141 and melanotan II are the other tryptophan-containing peptides in the catalogue and share the same light-protection requirement for the same reason.

References

Chemical, specification and analytical sources. This list is deliberately limited to chemistry and analytical references.

• Cayman Chemical, kisspeptin-10 (human) — formula, molecular weight, sequence
• Tocris, kisspeptin-10 — classification and specification data
• ChemicalBook, CAS 374675-21-5 — registry confirmation
• Bachem, Handling and Storage Guidelines for Peptides — deamidation, tryptophan photolability, solution stability

Cosmic Aminos supplies this material as a laboratory reagent for in-vitro research use only. It is not a drug, food, cosmetic or dietary supplement, is not approved by the Food and Drug Administration for any use, and is not for human or veterinary consumption. No dosing, administration or preparation guidance is provided.