Dr. Murai Éva szerk.: Parasitologia Hungarica 12. (Budapest, 1979)
Parasit. Hung. 12. 1979. Fasciola hepatica (L., 1758): Studies on Protease and Protease Inhibitor Activity Éva HAJDÚ — Dr. István MATSKÁSI — Dr. Sándor JUHÁSZ Veterinary Medical Research Institute, Hungarian Academy of Sciences, Budapest "Fasciola hepatica (L., 1758): Studies on protease and protease inhibitor activity" Hajdú, É. - Matskási, I. - Juhász, S. - Parasit. Hung. ^2. 21-30. 1979. ABSTRACT. Proteolytic enzyme and protease inhibitor activities were demonstrated in somatic extracts and maintenance media of liver flukes (Fasciola hepatica) . Against previous observations the extract and the medium reveals BAEE- and BTEEsplitting activities also at alkaline pH (8.0). The somatic extract inactivates the esterolytic effect of bovine trypsin and chymotrypsin. In vitro maintained live flukes, too, were able to decrease the activity of bovine proteases added to the medium, even after sealing of their oral sucker with the tissue cement Histoacryl. The liver fluke (Fasciola hepatica) derives its nutrients from the liver tissue and blood (HALTON, 1967). The muscular oral sucker and oesophageal suction play a decisive role in the mechanism of nutrient intake, but it has been postulated that proteolytic enzymes released by the parasite may also coUaborate in the digestion of host tissue. The involvement of parasite proteases in the nutrition process has been implied from light and electron microscopic observations (THORSELL and BJÖRKMAN, 1965; HALTON, 1963, 1967; HOWELL, 1973. PENNOIT de COOMAN and van GREMBERGEN (1942) were the first to detect proteolytic enzyme activity against a natural protein (casein) in extracts prepared from liver fluke homogenates; they designated the parasite protease tentatively as cathepsin C. In more detailed studies LOCATELLI and BERETTA (1969) established and acid pH optimum (range: 1. 8 - 3.0) of the enzyme activity on haemoglobin substrate, and inactivity of the protease at a neutral pH. An in vitro release of protease by the liver fluke was verified by THORSELL and BJÖRKMANN (1965), and later by LOCATELLI and BERETTA (1969) on the basis of gelatinolysis. The flukes placed in a gelatine-containing maintenance medium produced a lysis of gelatin, signs of which were most conspicuous around the oral region. Flukes with a ligated oral part failed to produce gelatinolysis. Histological examinations suggested that the proteolytic enzymes arise by synthesis in the parasite gut rather than by release from digested host tissues (Thorsell and Björkman, 1965; HOWELL, 1973; Halton, 1967). The protease inhibitors produced and released by the parasite play an important role in host-parasite interaction. Certain authors (PAPPAS and READ, 1972a; JUHÁSZ, 1979) belive that such inhibitors protect the parasite itself, or its more sensitive organs, against the proteolytic enzymes (trypsin, chymotrypsin) of the host. Evidence of the release of protease inhibitors has up to now been obtained in several Nematode ( Ascaris suum, Ascaridia galli , Nippostrongylus brasiliensis) and tapeworm species (Ligula intestinalis, Proteocepha- lus longicoUis) (von BRAND, 1973; KASSAI and TOTH, 1969; KENINA, 1971; JUHÁSZ, 1979; PAPPAS and READ, 1972a, b; REICHENBACH-KLINKE and REICHENBACH-KLINKE, 1970; MATSKÁSI and JUHÁSZ, 1977). Only a single attempt has been reported at the detection of protease inhibitors in 2 I
