Allatostatins from the retrocerebral complex and antennal pulsatile organ of the American cockroach: structural elucidation aided by matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry

The occurrence of allatostatins in retrocerebral complexes and antennal pul satile organs of the American cockroach, Periplaneta americana, was investi gated. Previously, molecular cloning of the P. americana allatostatin gene had predicted 14 peptides of this family [Ding et al., Comparison of the al latostatin neuropeptide precursors in the distantly related cockroaches Per iplaneta americana and Diploptera punctata. Pur J Biochem 1997;234:737-746] , however, only two forms had been identified by peptide isolation procedur es [Weaver et al., Identification of two allatostatins from the CNS of the cockroach Periplaneta americana: novel members of a family of neuropeptide inhibitors of insect juvenile hormone biosynthesis. Comp Biochem Physiol 19 94;107(C):119-127]. Using an extract of only 200 corpora cardiaca/corpora a llata, we have found that at least 11 allatostatins occur in the retrocereb ral complex. These peptides were already separated from other substances of the crude extract in the first HPLC step with heptafluorobutyric acid as o rganic modifier, and subsequently identified by MALDI-TOF mass spectrometry . Moreover, we have demonstrated the occurrence of nearly all allatostatins , including the cleavage product of Pea-AST-2 (LPVYNFGL-NH2), in antennal p ulsatile organs of males and females. Allatostatins are predominant neurope ptides in these organs. Additionally, only two other known peptides could b e identified in these organs by mass screening: proctolin and leucomyosuppr essin. The function of allatostatins in antennal pulsatile organs remains u nclear. We assume a release into the hemolymph via the ampullac, which coul d act as neurohemal release sites. The method described for the identificat ion of allatostatins is a very fast method for neuropeptide screening in ne urohemal tissues. (C) 1999 Elsevier Science B.V. All rights reserved.