Trematode peptidases are important molecules responsible for biocatalysis in many basal biological processes and are crucial in host-parasite interactions. Therefore, these enzymes are intensively studied in order to characterize their biological functions and to use them as potential diagnostic or therapeutic targets. Lately, investigation of transcriptome and secretome revealed, that adult Fascioloides magna (giant liver fluke) expresses and secretes a variety of peptidases. Thus, this thesis focuses on three newly identified enzymes: cathepsin L (FmCL), cathepsin B (FmCB) and cathepsin D (FmCD). In other trematode species, these cathepsins are being linked mainly with the digestion of host blood. We applied quantitative PCR (qPCR) to investigate relative expression levels of the three enzymes among three developmental stages - egg, miracidium and adult. It was revealed that all cathepsins have the highest expression in adult flukes in comparison to eggs and miracidia. We also localized the place of transcription of FmCL, FmCB and FmCD in adult fluke using RNA in situ hybridization. All of the peptidases were detected in gastrodermis, and in addition, they were localized in the reproductive system. The latter surprising finding is suggesting that these enzymes might have multiple functions in adult F....

Two isoforms of the tick Ixodes ricinus digestive peptidases cathepsins L1 and L3 are expressed also in salivary glands. In order to assess their role in this tissue, the specific antibodies against these peptidases were prepared by affinity chromatography and used for their detailed immuno-localization using cutting-edge methods of electron microscopy.

The hard tick Ixodes ricinus is an important blood-feeding parasite that transmits tick- borne diseases, such as tick-borne encephalitis and Lyme disease. Ticks employ a battery of proteolytic enzymes, including cathepsins, to digest their bloodmeal. These proteins are potential targets for the development of anti-tick vaccines. This work is focused on cathepsin L from I. ricinus (IrCL), namely its isoenzymes IrCL1 and IrCL3. IrCL1 was expressed in Pichia pastoris and chromatographically purified. Its substrate specifity was determined by the cleavage of (a) peptide fluorogenic substrates and (b) protein substrates analyzed by mass spectrometry. The proteolytic activity of IrCL1 was modulated by its interaction with glycosaminoglycans, which affected the pH optimum value. Futhermore, a proteolytically active mutant of IrCL1 with reduced number of N-glycosylation sites was prepared; this form will be used for crystallization experiments. IrCL3 was expressed in Escherichia coli, refolded and activated to its active form. The proteolytic activity of IrCL3 is in many ascpects similar to that of IrCL1, including substrate specifity, acidic pH optimum and activity modulation by glycosaminoglycans. Key words: cysteine proteases, cathepsin L, hard tick I. ricinus, substrate specifity, proteolytic activity...

Fascioloides magna (the giant liver fluke) originated from North America, is known in the Czech Republic since 1930s. This pathogenic fluke invades mostly cervids, but livestock too. Excretory-secretory products (ES products) contain number of esential biomolecules which are produced by excretory and secretory system of the fluke. These molecules play key role in many biological process during the life cycle not only of fascioloid flukes (e.g. migration in the host tissues, immune evasion and digestion). Due to their antigenic properties they could be also used in immunodiagnostics. Excretory-secretory proteins from adult Fascioloides magna and comparative related species Fasciola hepatica were purified and separated by the basic biochemical methods (1D, 2D electrophoresis, ion-exchange chromatography) and their activity was confirmed by specific (fluorogenic peptide) and nonspecific (gelatine) substrates. By using the mass spectrometry methods (MALDI TOF/TOF), the most abundant peptidolytically active proteins from ES products of F. magna were identified as cathepsin L (FmCL). Recombinant analog of FmCL was expressed in Pichia pastoris expression system. The peptidolytic activity was again confirmed using the synthetic fluorogenic substrates; the specifity of recombinant FmCL active site was...