Identification and bioactivity evaluation of the first neuropeptide from the lesser-known insect order Embioptera (webspinner).

A species of the poorly studied order Embioptera, the webspinner Oligotoma saundersii, is investigated for its complement of neuropeptides of the adipokinetic hormone (AKH) family. A methanolic extract of its corpora cardiaca (CC) is able to effect carbohydrate mobilization in the cockroach, Periplaneta americana, and liquid chromatography coupled to electrospray ionization mass spectrometry clearly identified one decapeptide as a member of the AKH family in the CC of O. saundersii. The primary structure of this peptide, code-named Olisa-AKH, is elucidated as pEVNFSPNWGG amide. It is a novel member of the AKH family and in its synthetic form it has strong hypertrehalosemic activity in the American cockroach. This effect may be explained by its near-identical structure compared with one of the endogenous cockroach AKH peptides. An analog with the reversed order of the proline and asparagine residues, viz. N(6)P(7)-Olisa-AKH, had negligible activity thus, shedding light on the requirements of the cockroach AKH receptor. From reversed-phase high-performance liquid chromatography experiments, we can conclude that the CC from an individual webspinner contains less than one pmol of Olisa-AKH. Comparison of the AKH sequences from the major orders of the Polyneoptera does not point to a close phylogenetic relationship between webspinners and stick insects.