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Infect. Immun., 04 1996, 1328-1334, Vol 64, No. 4
JP Dalton, KA Clough, MK Jones and PJ Brindley
Adult Schistosoma mansoni parasites synthesize and secrete both cathepsin L
and cathepsin B cysteine proteinases. These cysteine proteinase activities,
believed to be involved in hemoglobin digestion by adult schistosomes, were
characterized by using specific fluorogenic peptide substrates and
zymography. Both cathepsin L- and B-like activities with pH optima of 5.2
and 6.2, respectively, predominated in soluble extracts of worms, and both
these activities were secreted by adult worms into the culture medium. The
specific activity of cathepsin L was about double that of cathepsin B when
each was assayed at its pH optimum, and moreover, the specific activities
of cathepsins L and B in extracts of female schistosomes were 50 to 100%
higher than in extracts of male schistosomes. Analysis of the primary
structure of two cloned S. mansoni cathepsins L, here termed cathepsin L1
and cathepsin L2, revealed that they are only 44% similar and that
cathepsin L2 showed more identity (52%) with human cathepsin L than with
schistosome cathepsin L1. Moreover, differences in their active site,
propeptide region, and potential for glycosylation suggest separate
functions for schistosome cathepsin L1 and cathepsin L2.
Copyright © 1996, American Society for Microbiology
Characterization of the cathepsin-like cysteine proteinases of Schistosoma mansoni
Molecular Parasitology Unit, Queensland Institute of Medical Research, Australia.
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