PROTEINASE ACTIVITY IN THE PLEROCERCOID OF PROTEOCEPHALUS-AMBLOPLITIS(CESTODA)

Host invasion and tissue migration of several helminths have been link ed to expression and release of parasite-derived proteinases. The pler ocercoid of the cestode Proteocephalus ambloplitis can migrate into th e visceral organs or, in the case of bass, from them into the intestin al tract of the same individual fish. It does this within a few hours, aided by secretion of a substance from its apical gland. Proteinase a ctivity in this plerocercoid, obtained from the host liver, was define d by pH optimum, by substrate and inhibitor specificity, and by electr ophoretic and chromatographic techniques. Homogenates of plerocercoid contained a metalloproteinase exhibiting a molecular weight of 30 000 determined by gelatin substrate gel electrophoresis. Peak activity of this proteolytic enzyme in gel filtration fractions when azocoll was u sed as substrate then corresponded to a molecular weight of 31 500. Th e proteinase showed collagenolytic, haemoglobinolytic and slight elast inolytic activity, and it had a pH optimum at 9.0. Enzyme activity cou ld be inhibited by various chelating agents. The metalloproteinase ide ntified in this study constitutes the only enzyme class present in thi s larval stage of P. ambloplitis. We suggest that the plerocercoid's m etalloproteinase is the substance secreted from the apical organ, nece ssary for the previously recognized tissue migration phase. This enzym e might also have a nutritional function.