Leupeptin alters the proteolytic processing of P126, the major parasitophorous vacuole antigen of Plasmodium falciparum

Among several protease inhibitors tested, only leupeptin was found to modify qualitatively the processing of P126, a major antigen of the parasitophorous vacuole of Plasmodium falciparum, and to inhibit the release of merozoites. Whereas P126 is normally processed upon merozoite release into 2 polypeptides of 50 and 73 kDa which are discharged in the culture medium, leupeptin treatment led to the recovery of a 56 kDa fragment which was recognized by a monoclonal antibody specific for the 50 kDa polypeptide and of a 73 kDa fragment comigrating with the one obtained in normal culture conditions. Mild trypsinization of the 56 kDa polypeptide gave rise to a 50 kDa product the tryptic fragments of which comigrated with those of the 50 kDa antigen obtained from untreated cultures.