Identification of multiple peptides homologous to cockroach and cricket allatostatins in the stick insect Carausius morosus

Eighteen peptides were isolated from brain extracts of the stick insect Car ausius morosus. The peptides were purified in four steps by high-performanc e liquid chromatography, monitored by their ability to inhibit juvenile hor mone biosynthesis by corpora allata of the cricket Gryllus bimaculatus in v itro, and chemically characterised by Edman degradation and mass spectromet ry. We obtained complete primary-structure information for nine peptides, f our of which belong to the peptide family characterised by a common C-termi nal pentapeptide sequence -YXFGLamide. The remaining five belong to the W(2 )W(9)amide peptide family, nonapeptides characterised by having the amino a cid tryptophan in positions 2 and 9. The amino-acid sequence of two other p eptides could not be completely resolved by means of Edman degradation; how ever, these peptides could be allocated to the -YXFGLamide and the W(2)W(9) amide family, respectively, by comparison of retention times, co-elution an d mass spectrometry. Both classes of neuropeptides strongly inhibit juvenil e hormone biosynthesis in crickets but show no inhibiting effect on the cor pora allata of the stick insect. (C) 2000 Elsevier Science Ltd. All rights reserved.