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Taenia saginata oncosphere excretory/secretory peptidases
A C White1, S Baig, P Robinson
1Department of Medicine, Baylor College of Medicine, Houston, Texas, USA.
Abstract:
To identify oncosphere excretory/secretory peptidases, Taenia saginata adult worms were collected from 3 patients. Eggs were hatched and activated in vitro and oncospheres cultured in vitro. The culture medium from the oncospheres was assayed with peptide substrates coupled to 7-amino-4-trifluoromethyl coumarin (AFC), and free AFC was detected fluorometrically. The endopeptidase substrates Z-Phe-Arg-AFC and Z-Arg-AFC as well as the aminopeptidase substrate Arg-AFC were hydrolyzed when incubated with spent media from the oncospheres compared to control culture medium removed prior to incubation. Hydrolysis of Z-Phe-Arg-AFC was inhibited 78% by preincubation of the medium with the serine proteinase inhibitor Phenylmethylsulfonyl fluoride. Endopeptidase activity was partially enhanced in the presence of exogenous thiols and partially inhibited with the cysteine proteinase inhibitor E-64, suggesting the presence of both serine and cysteine endopeptidases. No significant inhibition was noted with pepstatin or phenanthroline. The peptidase activities detected with Z-Phe-Arg-AFC and Arg-AFC were separated by gel-filtration fast protein liquid chromatography and eluted at volumes corresponding to molecular weights of 18 and 30 kDa, respectively. These data demonstrate that T. saginata oncospheres produce excretory/secretory peptidases, including serine and cysteine endopeptidases and an aminopeptidase. These enzymes may play a role in invasion of the intestinal mucosa of the intermediate host.
Insights
Taenia saginata oncospheres secrete peptidases, including serine and cysteine endopeptidases and an aminopeptidase. These enzymes may aid in the parasite
Area of Science:
- Parasitology
- Biochemistry
Background:
- Taenia saginata is a parasitic cestode causing taeniasis.
- Oncospheres are the larval stage of tapeworms, responsible for infecting intermediate hosts.
Purpose of the Study:
- To identify and characterize excretory/secretory peptidases produced by Taenia saginata oncospheres.
- To investigate the potential role of these enzymes in host-parasite interactions.
Main Methods:
- Taenia saginata adult worms were obtained from patients.
- Oncospheres were cultured in vitro, and their culture medium was collected.
- Peptidase activity was assayed using fluorometric peptide substrates.
- Enzyme inhibition studies were performed using specific protease inhibitors.
- Gel-filtration fast protein liquid chromatography was used for enzyme separation.
Main Results:
- Taenia saginata oncosphere excretory/secretory products hydrolyzed various peptide substrates, indicating peptidase activity.
- Serine and cysteine endopeptidases, along with an aminopeptidase, were identified.
- Phenylmethylsulfonyl fluoride significantly inhibited serine endopeptidase activity.
- E-64 partially inhibited cysteine endopeptidase activity.
- Separated enzymes corresponded to molecular weights of 18 kDa and 30 kDa.
Conclusions:
- Taenia saginata oncospheres secrete active peptidases, including serine and cysteine endopeptidases and an aminopeptidase.
- These enzymes likely play a crucial role in the invasion of the intermediate host's intestinal mucosa.
- Further research into these peptidases could reveal potential targets for therapeutic intervention.