CHARACTERIZATION AND CLONING OF THE CATHEPSIN-L PROTEINASES OF SCHISTOSOMA-JAPONICUM

Adult Schistosoma japonicum parasites synthesize and secrete both cath epsin L and cathepsin B cysteine proteinases. The specific activities of cathepsin L were many-fold higher than that of cathepsin B. The cDN As encoding two distinct cathepsin L proteinases, here termed cathepsi n L1 and L2, were isolated. The deduced amino acid sequences of the ma ture cathepsin L1 and L2 were similar to 41% identical, and moreover, S. japonicum cathepsin L2 showed more similarity with human cathepsin L than with schistosome cathepsin L1. Schistosome cathepsin L proteina ses may be involved in the digestion of hemoglobin obtained from host erythrocytes. However, since we detected their presence in schistosome eggs, the release of these enzymes by eggs trapped in the liver and o ther organs may be associated with the granulomatous responses which c haracterize the pathology of human schistosomiasis. (C) 1995 Academic Press, Inc.