ISOLATION AND STRUCTURAL ELUCIDATION OF 2 PYROKININS FROM THE RETROCEREBRAL COMPLEX OF THE AMERICAN COCKROACH

By monitoring the contractile activity of the hyperneural muscle of th e American cockroach in vitro two peptides were isolated from the retr ocerebral complex of the American cockroach. Three purification steps using reversed-phase high performance liquid chromatography on C-18 co lumns containing trifluoroacetic acid or heptafluorobutyric acid as or ganic modifiers were sufficient to achieve homogenous peptide preparat ions. The structures of both peptides were elucidated by a combination of Edman degradation and mass spectrometry which yielded the followin g structures: His-Thr-Ala-Gly Phe-Ile-Pro-Arg-Leu-NH2 (Pea-PK-1) and S er-Pro-Pro-Phe-Ala-Pro-Arg-Leu-NH2 (Pea-PK-2). The C-terminal sequence Phe X-Pro-Arg-Leu-NH2 characterized the peptides as members of the in sect pyrokinin family. The synthetic peptides were shown to have the s ame retention times as the natural peptides. The occurrence of both pe ptides in the retrocerebral complex suggests a physiological role as n eurohormones. The effects of the synthetic pyrokinins were clearly dis tinguishable in their actions on the hyperneural muscle. Regarding the threshold concentrations, Pea-PK-2 was only 0.3% as active as Pea-PK- 1. (C) 1997 Elsevier Science Inc.