SCHISTOSOMES EXPRESS 2 FORMS OF CATHEPSIN-D

We report here a cDNA and its deduced amino acid sequence encoding a c athepsin D-like, aspartic protease expressed by adult stages of the hu man blood fluke Schistosoma mansoni. The cDNA encodes a short signal p eptide, a pro-enzyme peptide of 37 amino acid residues, and a mature e nzyme of 377 residues which has strong homology with mammalian catheps ins D. This aspartic protease, although 84% identical in amino acids o f the mature enzyme region to the previously reported cathepsin D from the Asian schistosome S. japonicum, differs remarkably from the S. ja ponicum enzyme in having a carboxyl terminal extension of 43 amino aci d residues. These cathepsins D of schistosomes may play pivotal roles in the degradation of hemoglobin obtained by the parasites from ingest ed host erythrocytes. (C) 1997 Elsevier Science B.V.