Identification and partial characterization of the proteases from different developmental stages of Schistocephalus solidus (Cestoda: Pseudophyllidae).

The proteolytic activities of extracts prepared from procercoids and plerocercoids as well as adults of the pseudophyllidean cestode Schistocephalus solidus were examined using several proteins and synthetic peptides as substrates. Whole bodies of procercoids and the isolated syncytial tegument of plerocercoids and adults prepared by freeze-thaw were studied. Extracts of procercoids contained a chymotrypsin-like proteinase exhibiting a molecular weight of 23,500 determined by gel filtration chromatography. The proteinase showed collagenolytic activity and had a pH optimum at 8. Such a proteinase was absent in plerocercoids and adults. In these developmental stages leucine aminopeptidases were detected in the isolated syncytial tegument having molecular weights of 93,500 (plerocercoids) and 89,000 (adults), respectively. The aminopeptidases in both stages displayed optimal activity at pH 8.5. The chymotrypsin-like proteinase of the procercoid is possibly necessary for the penetration of the host's intestinal wall, whereas the aminopeptidases of the plerocercoid and the adult of S. solidus may aid in parasite nutrition by degrading oligopeptides at the tegumental surface.