Identification of the adipokinetic hormone of the large milkweed bug Oncopeltus fasciatus

The adipokinetic hormone (AKH) of the large milkweed bug Oncopeltus fasciatus is isolated from an acidified methanolic extract of 200 corpora cardiaca, purified by single step reversed phase high-performance liquid chromatography (HPLC) and N-terminally deblocked using pyroglutamate aminopeptidase. The sequence is identified by Edman degradation and matrix assisted laser desorption/ionization-time of flight mass spectroscopy as pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp amide. This structure is confirmed by chemical synthesis and coelution of native and synthetic peptide on HPLC. The AKH of O. fasciatus is identical to Tenmo-HrTH, a member of the adipokinetic/red pigment-concentrating hormone peptide family that had been isolated earlier from several tenebrionid beetles. Tenmo-HrTH causes a significant rise in the concentration of haemolymph lipids when injected into adult male and female O. fasciatus, but displays no hyperglycaemic activity. There is no indication of the presence of other AKHs in O. fasciatus. The large milkweed bug represents the first member of the seed bugs (Lygaeidae) for which the endogenous AKH has been identified.