Kisspeptin-54 is a peptide ligand of the orphan G protein-coupled receptor GPR54 (Kis = 1.81 and 1.45 nM for rat and human receptors, respectively).1 It is a 54 amino acid peptide encoded by the metastasis suppressor gene KISS-1. Kisspeptin-54 induces calcium mobilization in CHO-K1 cells expressing rat and human receptors (EC50s = 1.39 and 5.47 nM, respectively). It also induces arachidonic acid release in CHO cells expressing rat and human GPR54 in a concentration-dependent manner. Kisspeptin-54 (10-1,000 nM) inhibits insulin secretion from isolated mouse pancreatic β-cells in the presence of 2.8 mM, but not 11.1 mM, glucose.2 Kisspeptin-54 (1-5 nmol, i.c.v.) increases serum levels of luteinizing hormone (LH) and follicular stimulating hormone (FSH) in mice, an effect which is reversed by the gonadotropin releasing hormone (GNRH) antagonist acycline.3

References
1. Kotani, M., Detheux, M., Vandenbogaerde, A.L., et al. The metastasis suppressor gene KiSS-1 encodes kisspeptins, the natural ligands of the orphan G protein-coupled receptor GPR54. J. Biol. Chem. 276(37), 34631-34636 (2001).
2. Vikman, J., and AhrÉn, B. Inhibitory effect of kisspeptins on insulin secretion from isolated mouse islets. Diabetes Obes. Metab. 11(Suppl 4), 197-201 (2009).
3. Gottsch, M.L., Cunningham, M.J., Smith, J.T., et al. A role for kisspeptins in the regulation of gonadotropin secretion in the mouse. Endocrinology 145(9), 4073-4077 (2004).