Aminopeptidases as Immobilized Enzymes on the Peritrophic Membranes of Insects
Peters, Werner; Kalnins, Monika
Evidence could be obtained for the presence of aminopeptidases on peritrophic envelopes and peritrophic membranes as well as the apical parts of the midgut cells of the following species of insects: Locusta migratoria Von Linne 1761 [Saltatoria], Acheta domestica Linnaeus 1758 [Saltatoria], Forficula auricularia Linnaeus 1758 [Dermaptera], Periplaneta americana (Linnaeus 1758) [Blattodea], Blaberus giganteus Linnaeus 1758 [Blattodea], Pachnoda sp. [Coleoptera], Apis mellifera Linnaeus 1758 [Hymenoptera], and Phormia terrae-novae Robineau-Desvoidy 1830 [Diptera]. Differences occurred between the species in the degree of staining and the extent of the stainable areas along the midgut. Electron microscopic investigations showed that aminopeptidases may be present on both sides and also in the peritrophic envelope of cockroaches which consist of numerous peritrophic membranes. The aminopeptidases seem to adhere to the peritrophic membranes of cockroaches rather firmly as there was no recognizable decrease in staining if the peritrophic membranes were washed several times and if they remained in phosphate buffer for up to 2 hours. These enzymes are probably longer conserved as immobilized enzymes whereas soluble enzymes in the lumen of the peritrophic envelope are shed more quickly with the faeces.