Isolation and identification of AKH/RPCH family peptides in blister beetles (Meloidae)

Abstract

Abstract. Two peptides were isolated from methanolic extracts of corpora cardiaca of the blister beetle, Decupotoma 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‐Am‐Trp‐Gly‐AsnNH2 and (2) pGlu‐Leu‐Asn‐Phe‐Ser‐Pro‐Asn‐TrpNH2, 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 (Decupotoma 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 Decupotoma lunata nor the synthetic peptides Del‐CC and Tem‐HrTH were active in mobilizing carbohydrates or lipids in the blister beetle.