title: Proteolytic breakdown of the Neb-trypsin modulating oostatic factor (Neb-TMOF) in the hemolymph of different insects and its gut epithelial transport.
abstract: The degradation of the unblocked hexapeptide, trypsin modulating oostatic factor of the flesh fly Neobellieria (Sarcophaga) bullata (Neb-TMOF) was studied in vitro in the hemolymph of the lepidopteran Spodoptera frugiperda, the orthopteran Schistocerca gregaria and the dictyopteran Leucophaea maderae. The half-life in the different species varied from approximately 3min in L. maderae to approximately 25min in S. gregaria. Purification of the degradation products and ESI-Qq-oa-Tof mass spectrometry revealed the fragments Asn-Pro-Thr-Asn, Leu-His and Asn-Pro, which were the same in the hemolymph of all species. Except in Leucophaea, Neb-TMOF was cleaved in dipeptides starting from the C-terminus and the reaction could be, at least partially, inhibited by captopril. These observations suggest that a dipeptidase, which has very similar enzymatic properties as mammalian angiotensin converting enzyme (ACE) and which circulates in the hemolymph, apparently is involved in the breakdown of Neb-TMOF and might be a common but not a universal enzyme in insect hemolymph.The introduction of Neb-TMOF into the gut of S. gregaria with the help of a capillary tube (intubation) demonstrated that the intact peptide is able to cross the gut epithelium and to appear in the hemolymph compartment. Since [3H]-inulin, which is too large to cross cell membranes, was found to penetrate the gut walls at a measurable rate, the paracellular pathway might be also permeable to smaller peptides. There was indeed a clear correlation between the molecular weight of inulin, Neb-TMOF, and inositol and the rate of penetration of these compounds through the gut epithelium to the hemolymph. These are promising findings in view of a potential use of such peptides for insect control purposes.
authors.affiliation: Zoological Institute, Katholieke Universiteit Leuven, Naamesestraat 59, B-3000, Leuven, Belgium
authors.forename: W
authors.initials: W
authors.lastname: Zhu
authors.forename: A
authors.initials: A
authors.lastname: Vandingenen
authors.forename: R
authors.initials: R
authors.lastname: Huybrechts
authors.forename: T
authors.initials: T
authors.lastname: Vercammen
authors.forename: G
authors.initials: G
authors.lastname: Baggerman
authors.forename: A
authors.initials: A
authors.lastname: De Loof
authors.forename: C P.
authors.initials: CP
authors.lastname: Poulos
authors.forename: A
authors.initials: A
authors.lastname: Velentza
authors.forename: M
authors.initials: M
authors.lastname: Breuer