Cysteine proteinases from Schistosoma haematobium adult worms

To identify and characterize cysteine proteinases from Schistosoma haematobium, lyophilized adult worms were homogenized, and enzymes were isolated and purified. From extracts prepared in acidic buffer, 3 putative cysteine proteinases were identified either directly or indirectly. The first proteinase (ShCP1) was identified by labeling with a radioiodinated inhibitor, Z-Tyr-Ala-CHN2, as a 35-kDa protein. However, it could not be detected by silver staining, amino acid sequencing, or by a monoclonal antibody specific for a similar molecule from Schistosoma mansoni. A second cysteine proteinase, ShCP2, was purified by gel filtration and dialysis. This 32-kDa molecule was thiol-dependent and was labeled with Z-Tyr-Ala-CHN2. The amino terminal amino acid sequence of ShCP2 showed remarkable similarity (up to 77%) to that of S. mansoni cathepsin B (SmCP2) as well as to mammalian cysteine proteinases. Both ShCP1 and ShCP2 reacted with polyclonal antibodies against S. mansoni, suggesting the existence of shared antigenic epitopes. A third activity, ShCP3, was identified as possibly a distinct proteinase based on its similarities to a 28-kDa cysteine proteinase from S. mansoni. This preliminary investigation demonstrates that the overall profile of cysteine proteinases in S. haematobium is very similar to that of S. mansoni.