Abstract:
Cercariae of the bird schistosome Trichobilharzia regenti and of the human schistosome Schistosoma mansoni employ
proteases to invade the skin of their definitive hosts. To investigate whether a similar proteolytic mechanism is used by both
species, cercarial extracts of T. regenti and S. mansoni were biochemically characterized, with the primary focus on cysteine
peptidases. A similar pattern of cysteine peptidase activities was detected by zymography of cercarial extracts and their
chromatographic fractions from T. regenti and S. mansoni. The greatest peptidase activity was recorded in both species
against the fluorogenic peptide substrate Z-Phe-Arg-AMC, commonly used to detect cathepsins B and L, and was
markedly inhibited (>96%) by Z-Phe-Ala-CHN2 at pH 4.5. Cysteine peptidases of 33 kDa and 33–34 kDa were identified
in extracts of T. regenti and S. mansoni cercariae employing a biotinylated Clan CA cysteine peptidase-specific inhibitor
(DCG-04). Finally, cercarial extracts from both T. regenti and S. mansoni were able to degrade native substrates present in
skin (collagen II and IV, keratin) at physiological pH suggesting that cysteine peptidases are important in the pentration of
host skin.
