Isolation, primary structure, andsynthesis of locustapyrokinin: a myotropic peptide of Locusta migratoria

A neuropeptide which stimulates the motility of the cockroach hindgut has been isolated from an extract of 9000 brain-corpora cardiaca-corpora allata-subesophageal ganglion complexes of Locusta migratoria. Biological activity was monitored during HPLC purification by observing the myotropic effect of column fractions on the isolated hindgut of Leucophaea maderae. The primary structure of this myotropic peptide was established as a blocked 16-residue peptide: pGlu-Asp-Ser-Gly-Asp-Gly-Trp-Pro-Gln-Gln-Pro-Phe-Val-Pro-Arg-Leu-NH2. This novel locust peptide was designated as locustapyrokinin, or Lom-PK. Lom-PK was synthesized and shown to have chromatographic and biological properties identical to those of the native material. Lom-PK has a Phe-X-Pro-Arg-Leu-NH2 carboxy terminal in common with leucopyrokinin (or Lem-PK), a blocked myotropic neuropeptide isolated from the cockroach hindgut. The constituent amino acids of this C-terminal are important for biological activity on the Leucophaea hindgut. The primary structure of this novel insect peptide is, however, substantially different from Lem-PK at the amino-terminal sequence.