ISOLATION AND IDENTIFICATION OF AKH/RPCH FAMILY PEPTIDES IN BLISTER BEETLES (MELOIDAE)

Two peptides were isolated from methanolic extracts of corpora cardiaca of the blister beetle, Decapotoma lunata, by a single-step purification procedure, utilizing C-18 reversed-phase high-performance liquid chromatography (RP-HPLC) for separation, and the increase of haemolymph lipids in Locusta migratoria for bioassay. The native peptides were analysed by matrix-assisted laser-desorption ionization mass spectrometry revealing main ions at m/z 1180 and 1009 respectively which were attributed to the [M + Na](+) form of the respective peptides. After deblocking of the N-terminal pyroglutamate residue of each peptide, the structures of the deblocked peptides were determined by pulsed-liquid phase sequencing employing Edman chemistry. The sequences of the two peptides, (1) pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-Gly-AsnNH(2) and (2) pGlu-Leu-Asn-Phe-Ser-Pro-Asn-TrpNH(2), characterize them as deca- and octapeptide members of the AKH/RPCH family. Whereas the decapeptide is a novel member of this family and is given the acronym Del-CC (Decapotoma lunata corpus cardiacum peptide), the octapeptide has previously been found in tenebrionid beetles and has the acronym Tem-HrTH. The corpora cardiaca of two other species of blister beetles (Cyaneolytta pectoralis and Mylabris coeca) contain the same two peptides as D. lunata, as judged by RP-HPLC and biological activity. Neither a corpus cardiacum extract of Decapotoma lunata nor the synthetic peptides Del-CC and Tem-HrTH were active in mobilizing carbohydrates or lipids in the blister beetle.