The biologically active C-terminal region of mouse/rat Kisspeptin, with the leucine residue at position 8 of this peptide isotopically labelled with carbon-13 and nitrogen-15, giving a mass increase of 7 compared to the unlabelled peptide.

Kisspeptin, is cleaved from a 145 amino acid precursor to a 54 amino acid peptide in humans and a 52 amino acid peptide in mice. Smaller isoforms of 14, 13 and 10 amino acids have also been isolated, each sharing the common C-terminal sequence. Kisspeptin-10 (KP-10) is the most potent member of the kisspeptin family and the plasma half-life of is approximately 6 fold shorter than KP-54. KP-10 is produced by the trophoblast cells in the first trimester of pregnancy and inhibits cell migration of primary trophoblasts which is essential for placental invasion.

Kisspeptin, a product of the KISS1 gene, is a hypothalamic neuropeptide that stimulates gonadotropin-releasing hormone (GNRH) neurons and drives fertility. Kisspeptin binds specifically to the G-protein-coupled receptor-54, now known as Kiss1r, which is expressed in almost all GNRH neurons. Kiss1r is also expressed in other areas of the brain and periphery, highlighting other possible roles for kisspeptin outside of reproduction