Amine receptors (biogenic amine-binding GPCRs) belong to the Class A GPCR family. Biogenic amines are a collection of amines that have biological properties (hormones, neurotransmitters, neuromodulators). They are derived from aromatic amino acids. Orphan receptor is the term used to describe a GPCR for which the ligand has not been identified. (Adapted from PMID:17088868 and FBrf0193587).