Its principal ligand is bradykinin, a 9 amino acid peptide generated in pathophysiologic conditions such as inflammation, trauma, burns, shock, and allergy.

Tertiapin is a 21-amino acid peptide isolated from venom of the European honey bee (Apis mellifera).

Psalmotoxin is a 40-amino acid peptide, possessing 6 cysteines linked by three disulfide bridges.

ANP is a 28-amino acid peptide with a 17-amino acid ring in the middle of the molecule.

The 25-amino acid peptide of hepcidin is secreted by the liver and is considered the "master regulator" of iron metabolism.

Glucagon-like peptide-2 (GLP2) is a 33-amino acid proglucagon-derived peptide produced by intestinal enteroendocrine cells.

Iberiotoxin is a 37-amino acid peptide.

It was found to be an 18-amino acid peptide processed from the C-terminus of a 200-amino acid precursor, which is called prosystemin.

RDH12 is mainly expressed in neuroretina and is composed of 7 exons encoding a 360-amino acid peptide.