Isolation and structure of two gastrin/CCK-like neuropeptides from the American cockroach homologous to the leucosulfakinins.

Perisulfakinin, a peptide with sequence similarity to gastrin and cholecystokinin, was isolated from the corpora cardiaca of the American cockroach. Its sequence was determined to be Glu-Gln-Phe H-Asp-Asp-Tyr(SO3H)-Gly-His-Met-Arg-Phe-amide. The peptide induced hindgut contractions in the same species at concentrations as low as 250 pM. A related non-sulfated peptide was also isolated and sequenced; it was found to be identical with non-sulfated leucosulfakinin II (pGlu-Ser-Asp-Asp-Tyr-Gly-His-Met-Arg-Phe-amide). This peptide did not stimulate hindgut contractions. The structures of the cockroach peptides of the leucosulfakinin family are thus much more conserved than the cockroach hypertrehalosemic hormones.