Abstract: AIM:To identify the cathepsins in adult worms of Schistosoma japonicum and their proteolytic activities. METHODS: The vomitus from adult worms of S. japonicum was collected. The proteolytic activity of cathepsins in the vomitus was identified and measured using synthetic substrates with arginyl bonds. RESULTS: Specific synthetic substracts Z Arg Arg AMC (for cathepsin B) and Z Phe Arg AMC (for cathepsin B and L) were degraded by the vomitus. An inhibitor, Z Phe PheCHN 2 for cathepsin L , inhibited partialy the activity of
the vomitus to degrade Z-Phe-Arg-AMC. The optimal pH for cathep sin B/L is 5.0- 5.5.CONCLUSION: The vomitus of S. japonicum has cathepsin B-and L-like activity.

Key words: Schistosoma japonicum, cathepsins, proteolytic activity