title: Strategies for the isolation of insect peptides.
abstract: Two distinct diuretic peptides affect the rate of fluid secretion of the Malpighian tubules in Locusta. Diuretic peptide (DP 1) has a molecular mass ca. 4500 and acts via cyclic AMP: the second diuretic peptide (DP 2) has a molecular mass of ca. 1000 and operates via an unknown transduction mechanism; the possible involvement of cGMP, calcium mobilization and the breakdown of phosphoinositides has been investigated. Preliminary sequence data for DP 1 is reported and details are provided concerning the isolation and characterisation of a peptide which is present in large amounts in the storage lobes of the corpora cardiaca and co-chromatographs with DP 1 on high performance size-exclusion chromatography. Adipokinetic hormones (AKH) present in the corpora cardiaca of insects can regulate lipid metabolism. AKH occurs in two forms as AKH I and as AKH II: these hormones have been isolated and characterised in both Locusta and Schistocerca. AKH I is a decapeptide of the following structure: pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-ThrNH2 and is identical in Locusta and Schistocerca. AKH II is different in these two insects: AKH II-L from Locusta is: pGlu-Leu-Asn-Phe-Ser-Ala-Gly-TrpNH2 and AKH II-S from Schistocerca is: pGlu-Leu-Asn-Phe-Ser-Thr-Gly-TrpNH2. These structures have been established using newly developed quick and simple procedures employing HPLC and gas-phase sequencing which enables full structures to be elucidated from 2-3 nmoles of peptide. Comparisons are made between the structures of AKH and related peptides isolated from insects and crustacea.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004231:Diuresis; D007301:Insect Hormones / Q000302:isolation & purification* / Q000502:physiology; D007313:Insecta / Q000032:analysis* / Q000502:physiology; D008053:Lipid Mobilization; D010455:Peptides / Q000302:isolation & purification* / Q000502:physiology
chemical_list: D007301:Insect Hormones; D010455:Peptides