Evolution of vasopressins in marsupials: a new hormone, phenypressin (Phe2-Arg8-vasopressin), present in the Macropodidae

A duplication of the pressor hormone has been found in some marsupials, either American species belonging to the family Didelphidae or Australian species belonging to the family Macropodidae. Two pressor peptides, lysine vasopressin and phenypressin (Phe2-Arg8-vasopressin) have been chemically identified in the red Kangaroo (Macropus rufus) and the Tammar (Macropus eugenii). In contrast, the brush-tailed Possum (Trichosurus vulpecula), a species belonging to the family Phalangeridae, has a single pressor hormone, arginine vasopressin. Because this latter hormone was also found in a prototherian species, the Echidna, it might be assumed that it is the product of a primitive gene and that a duplication and subsequent mutations led to lysine vasopressin and phenypressin in Macropodidae.