Expression of an active cathepsin B-like protein Sm31 from Schistosoma mansoni in insect cells.

Recombinant Schistosoma mansoni cathepsin B was produced in insect cells via the baculovirus expression vector system as a 37.5 kDa precursor molecule and a 31 kDa mature enzyme. Extracts prepared from cells infected with the recombinant virus were able to cleave a synthetic dipeptide substrate specific for cathepsin B. Proteolytic activity was inhibited by trans-epoxysuccinyl-L-leucyl-amido (4-guanidino) butane (E64) but not by phenylmethylsulphonyl-fluoride (PMSF), pepstatin and 1,10-phenanthroline. Specific inhibition by diazomethylketone derivatives, which bind covalently to the active centre of cysteinyl proteinases was also demonstrated.