A comparative survey of the hydrolytic enzymes of ectoparasitic and free-living mites

Extracts of ectoparasitic miles of birds (Dermanyssus gallinae), sheep (Pso roptes ovis) and plants (Tetranychus urticae) and of free-living mites (Aca rus siro) contained acid and alkaline phosphatase, C4 and C8 esterases, lip ase, leucine and valine aminopeptidases and a range of glycosidase activiti es. Dermanyssus gallinae and P. ovis, species highly adapted to an animal p arasitic lifestyle. had very similar profiles and contained low activities of glycosidases. In contrast, the polyphagous species A. siro contained mod erate to high activities of every glycosidase examined, whereas the phytoph agous species, T. urticae, displayed high activities of only beta-galactosi dase and beta-glucuronidase, All extracts hydrolysed haemoglobin with optim a below pH 6. and this hydrolysis was associated with an aspartic proteinas e and variable cysteine proteinase activity dependent on species. Inhibitor -labelling with biotinyl-Phe-Ala-FMK revealed the presence of cysteine prot einases with molecular masses of 25-33.5 kDa. Each mite species contains th e enzymes necessary to complete digestion of the diet in the intracellular lysosomal compartment. The absolute and relative activities of each enzyme varied. and are discussed according to phylogeny and dietary habit. (C) 200 0 Australian Society for Parasitology Inc. Published by Elsevier Science Lt d. All rights reserved.