Cicadas Contain Novel Members of the AKH/RPCH Family Peptides with Hypertrehalosaemic Activity

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Abstract
Two new members of the adipokinetic hormone/red pigment-concentrating hormone (AKH/RPCH) family of peptides were identified in the cicadas Platypleura capensis and Munza trimeni using heterologous (in migratory locusts and cockroaches) and homologous (in P. capensis) bioassays. The two peptides were isolated from the corpora cardiaca of the two cicada species by reversed-phase high performance liquid chromatography. Edman sequencing after deblocking the N-terminal 5-oxopyrrolidine-2-carboxylic acid residue revealed that both peptides have the amino acid sequence (pGlu)-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Asn. Mass spectrometry, however, showed that peptide 1 (eluting first on HPLC) had a mass 352 Dalton higher than peptide 2; the exact modification of peptide 1 is not known yet. The N- and C-terminal blocked decapeptide 2 was synthesised and shown to be chromatographically indistinguishable from the natural compound under various HPLC conditions. Because this synthetic peptide increases the carbohydrate concentration in the haemolymph of P. capensis when injected, it is named Plc-HrTH-II, Platypleura capensis hypertrehalosaemic hormone II. Flight experiments with P. capensis confirmed that this species uses carbohydrates for flight: glycogen in the flight muscle and carbohydrates in the blood decreased by 70% and 40%, respectively.

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