ADULT SCHISTOSOMA-MANSONI EXPRESS CATHEPSIN-L PROTEINASE ACTIVITY

This report presents the deduced amino sequence of a novel cathepsin L proteinase from Schistosoma mansoni, and describes cathepsin L-like a ctivity in extracts of adult schistosomes. Using consensus primers spe cific for cysteine proteinases, gene fragments were amplified from adu lt S. mansoni cDNA by PCR and cloned. One of these fragments showed ma rked identity to Sm31, the cathepsin B cysteine proteinase of adult S. mansoni, whereas another different from Sm31 and was employed as a pr obe to isolate two cDNAs from an adult S. mansoni gene library. Togeth er these cDNAs encoded a novel preprocathepsin L of 319 amino acids; t his zymogen is predicted to be processed in vivo into a mature, active cathepsin L proteinase of 215 amino acids. Closest homologies were wi th cathepsins L from rat, mouse and chicken (46-47% identity). Souther n hybridization analysis suggested that only one or a few copies of th e gene was present per genome,demonstrated that its locus was distinct from that of Sm31, and that a homologous sequence was present in Schi stosoma japonicum. Because these results indicated that schistosomes e xpressed a cathepsin L proteinase, extracts of adult S. mansoni were e xamined for acidic, cysteine proteinase activity. Based on rates of cl eavage of peptidyl substrates employed to discriminate between classes of cysteine proteinases, namely cathepsin L (Z-phe-arg-AMC), cathepsi n B (Z-arg-arg-AMC) and cathepsin H (Bz-arg-AMC), the extracts were fo und to contain vigorous cathepsin L-like activity. In contrast, comple te inhibition of this activity was observed when the cathepsin L inhib itor Z-phe-ala-CHN2 was included which together demonstrated that the conspicuous, acidic cysteine proteinase activity in extracts of adult S. mansoni was cathepsin L-like. The cathepsin L may be crucial for sc histosome metabolism of host hemoglobin.