ASPARAGINYL ENDOPEPTIDASE ACTIVITY IN ADULT SCHISTOSOMA-MANSONI

Sequence comparisons have recently shown that the Schistosoma mansoni protein Sm32 is similar to asparaginyl endoproteinases, a novel family of cysteine proteinases, of which the legumains from legumes are the best characterized. By synthesizing and employing fluorogenic peptide substrates for the specific detection of asparaginyl endopeptidases, v ue have identified this type of activity in extracts of adult S. manso ni. The S. mansoni activity is similar to that of the legumains in its substrate specificity and sensitivity to thiol inhibitors, but differ s in its pH and temperature optima for activity. In contrast, unlike t he legumains, the schistosome asparaginyl endopeptidase activity is no t activated by the reducing agent dithiothreitol. As suggested for leg umains, Sm32 may function in the post-translational modification proce sses that regulate the activity of other molecules.