Isolation of a novel RFamide peptide from the midgut of the American cockroach, Periplaneta americana.

In insects (FM)RFamide-immunoreactive endocrine cells are ubiquitously present in the midgut, but the identity of the peptide(s) produced by these cells is unknown. The major RFamide-immunoreactive peptide from the midgut of the American cockroach, Periplaneta americana, was isolated and identified as Ala-Asn-Arg-Ser-Leu-Arg-Leu-Arg-Pheamide. This is a novel member of an arthropod peptide family, previously known only from mosquitoes and horseshoe crabs. Its abundance in the midgut suggests that it plays an important function in digestion.