title: The involvement of the cysteine proteases of Clonorchis sinensis metacercariae in excystment.
abstract: The effects of trypsin, bile, trypsin-bile, pepsin, dithiothreitol (DTT) and metacercarial excretory-secretory product (ESP) on the in vitro excystment of Clonorchis sinensis metacercariae were investigated. The majority of metacercariae excysted immediately in trypsin-bile in PBS solution, a process which was complete after 30 min of incubation. When incubated in metacercarial ESP in PBS, excystment was potentiated in the presence of 5 mM DTT, but was inhibited dose-dependently by a cysteine protease inhibitor, iodoacetic acid. Two active protease bands of 28 and 40 kDa were identified in the ESP of metacercariae by gelatin substrate SDS-PAGE. Scanning electron microscopy demonstrated that the larvae in solutions of DTT and ESP migrated through a small hole on the metacercarial wall, whereas larvae were liberated by entire wall disruption in trypsin solution. These results suggest that trypsin is a major extrinsic factor of the rapid excystment of C. sinensis metacercariae, and that endogenous cysteine proteases are also involved in metacercarial excystment.
authors.affiliation: Department of Parasitology and Tropical Medicine, Seoul National University College of Medicine and Institute of Endemic Diseases, Seoul National University Medical Research Center, Seoul 110-799, Korea.
authors.forename: Shunyu
authors.initials: S
authors.lastname: Li
authors.forename: Young-Bae
authors.initials: YB
authors.lastname: Chung
authors.forename: Byung-Suk
authors.initials: BS
authors.lastname: Chung
authors.forename: Min-Ho
authors.initials: MH
authors.lastname: Choi
authors.forename: Jae-Ran
authors.initials: JR
authors.lastname: Yu
authors.forename: Sung-Tae
authors.initials: ST
authors.lastname: Hong
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000494:pharmacology; D003004:Clonorchis sinensis / Q000201:enzymology / Q000502:physiology*; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D015801:Helminth Proteins / Q000494:pharmacology; D010434:Pepsin A / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology
chemical_list: D001647:Bile Acids and Salts; D015853:Cysteine Proteinase Inhibitors; D015801:Helminth Proteins; D014357:Trypsin; D003546:Cysteine Endopeptidases; D010434:Pepsin A; D004229:Dithiothreitol