PROTEOLYTIC DEGRADATION OF HOST HEMOGLOBIN BY SCHISTOSOMES

Schistosomes acquire amino acids for growth, development, and reproduc tion by catabolizing hemoglobin obtained from ingested host erythrocyt es. While the biochemical pathway(s) involved has not been determined definitively, a number of proteases including schistosome legumain and cathepsin L-, D-, B- and C-like enzymes have been ascribed roles in t he degradation of hemoglobin to diffusible peptides. Transcripts encod ing these schistosome proteases, which appear to be expressed in the g astrodermis and cecum of the schistosome, have been reported. Because these enzymes are candidate targets at which to direct novel anti-schi stosomal therapies, the comparative biochemistry of these and their co unterpart mammalian proteases is now the focus of research in a number of laboratories. This paper reviews reports dating from 40 years ago to the present on how schistosomes digest host-derived hemoglobin, and interprets apparent anomalies in some earlier compared to later repor ts, the latter having benefited from the availability of PCR and gene cloning technologies. More specifically, the review concentrates on fi ve proteolytic enzymes, and their associated genes, which have been as cribed key roles in the pathway of hemoglobin degradation. (C) 1997 El sevier Science B.V.