SCHISTOSOMA-MANSONI - ISOLATION AND CHARACTERIZATION OF SMPI56, A NOVEL PROTEASE INHIBITOR

Tegumental extracts from adult worms of Schistosoma mansoni contain an inhibitory activity to the S. mansoni 28-kDa serine protease and to p ancreatic elastase. By using biotinylated elastase and streptavidin-ag arose, the postulated protease inhibitor has been isolated from the cr ude worm extract in a single step. Monospecific rabbit antibodies rais ed against the protease inhibitor have immunoprecipitated a 56-kDa [S- 35]Met-labeled serine protease inhibitor which was designated Smpi56 ( S. mansoni protease inhibitor, 56 kDa). Smpi56 binds tightly to and in hibits the 28-kDa protease of S. mansoni and pancreatic and neutrophil elastase but not papain, pepsin, thrombin, trypsin, chymotrypsin, pro teinase K, urokinase and acetylcholinesterase. The biological function of Smpi56 is still not known, but in view of its elastase inhibitory activity it may be speculated that the parasite is employing Smpi56 to protect itself from activated neutrophils. Smpi56 may also potentiall y protect the parasite from its endogenous 28-kDa protease. (C) 1994 A cademic Press, Inc.