Kisspeptin-10: structure and analysis

What is Kisspeptin-10?

Kisspeptin-10 is the ten-amino-acid C-terminal fragment of kisspeptin, the peptide product of the KISS1 gene. The parent peptide is considerably longer; this fragment is the portion that carries the activity, which is why it is the form supplied.

It belongs to the RFamide family, meaning it terminates in arginine-phenylalanine with the C-terminus present as an amide rather than a free acid. The sequence also contains a tryptophan residue.

How is Kisspeptin-10 produced?

Assembled by solid-phase peptide synthesis: the chain is built one residue at a time on an insoluble resin support, then cleaved from the resin, deprotected and purified — most commonly by reversed-phase high-performance liquid chromatography. The purified material is lyophilized to a dry solid.

The impurity profile that appears on a certificate is a record of where that process was imperfect: deletion sequences from an incomplete coupling, truncated chains, and species retaining a protecting group.

What are the molecular figures for Kisspeptin-10?

Calculated from the formula C63H83N17O14, not measured. The average molecular weight counts the natural abundance of each element's isotopes; the monoisotopic mass is the mass of the single most abundant isotopic composition, which is the figure a mass spectrometer is usually compared against.

The expected ions follow from the monoisotopic mass by adding one proton per charge. They are a starting point for recognising a spectrum, not a substitute for one: adducts, salts, modifications and multiply charged species all move the observed m/z, and the certificate reports what was actually measured for a batch.

Adducts, salts, modifications and multiply charged species all move an observed m/z away from any figure calculated here, and a certificate reports what was measured for a batch rather than what was expected of it.

What is the sequence of Kisspeptin-10?

Kisspeptin-10 is 10 residues long. Written in the one-letter amino-acid code, as the cited record states it:

The sequence is what an identity test resolves. The mass a spectrometer is compared against is the mass this chain implies, which is why a single missing or substituted residue changes the result by an amount that cannot be mistaken for instrument variation — the deletion is detectable rather than invisible.

Sequence information describes the molecule, not the material in a vial. What establishes a specific batch is the identity method and result on its certificate.

How does Kisspeptin-10 compare with related compounds?

Related compounds are not interchangeable. Published figures differ between them, and in this catalogue three compounds share a GHRH backbone while several share the same structural class — which is exactly why identity is confirmed analytically rather than inferred from the label.

How is the identity of Kisspeptin-10 confirmed?

Mass spectrometry confirms the ten-residue chain and, importantly, the C-terminal amide. The amide and the free acid differ by roughly one mass unit, which is a small difference requiring high-resolution measurement to resolve confidently — and a difference that matters, because the free-acid form is a distinct compound.

Which impurities can appear in Kisspeptin-10?

The tryptophan residue is the analytically significant feature. Tryptophan is among the most readily oxidised and most light-sensitive amino acids, so oxidation products are a plausible impurity class and light protection is a reasonable handling precaution.

Incomplete C-terminal amidation is the other characteristic impurity, and because it produces only a small mass shift, it is a result that depends on the resolution of the identity method rather than being obvious from a low-resolution spectrum.

What does a certificate of analysis for Kisspeptin-10 report?

A certificate for a batch of this material names the batch, names the issuing laboratory, and states for each parameter both the method used and the specification the result was measured against. Identity and purity are the two core results; net peptide content states how much of the fill weight is actually peptide.

A certificate belongs to a batch, not to a product line. When a new batch is released it is tested again, and the certificate published against it is that batch's certificate — a previous batch's result is never carried forward.

Is Kisspeptin-10 for human use?

No. This page describes structure and analysis. It makes no claim about what this compound does, and none should be inferred from it. Material is supplied for laboratory research use only: it is not a drug, food, dietary supplement, cosmetic or medical device, it is not for human or veterinary consumption, and no dosing, administration or reconstitution guidance is provided for any such use.

References

• Kisspeptin-10 — PubChem, National Library of Medicine
• Metastasis-suppressor KiSS-1 — human — UniProt Knowledgebase
• Kisspeptin-10 — ChEMBL, European Bioinformatics Institute
• Molecular identification and functional characterization of the kisspeptin/kisspeptin receptor system in lower vertebrates — Biol Reprod, 2008