PEROXIDASE-ACTIVITY OF A TSA-LIKE ANTIOXIDANT PROTEIN FROM A PATHOGENIC AMEBA

The 29 kDa surface protein of Entamoeba histolytica is an abundant ant igenic protein expressed by pathogenic strains of this organism. The p rotein is a member of a widely-dispersed group of homologues which inc ludes at least two cysteinyl peroxidases, Salmonella typhimurium alkyl hydroperoxidase C-22 protein (AhpC) and Saccharomyces cerevisiae thio l-specific antioxidant protein (TSA). Here, for the first time in a pa thogenic eukaryote, we have demonstrated that the amoebic protein also possesses peroxidatic and antioxidant activities in the presence of r eductants such as dithiothreitol or thioredoxin reductase plus thiored oxin. Although the S. typhimurium AhpF flavoprotein was not an effecti ve reductant of the amoebic TSA protein, one inhibitory monoclonal ant ibody directed toward amoebic TSA was also partially inhibitory toward reduced but not oxidized bacterial AhpC. These antioxidant proteins a re likely to be important not only in general cell protection, but als o in the promotion of infection and invasion by these pathogenic organ isms through protection against oxidative attack by activated host pha gocytic cells. (C) 1997 Elsevier Science Inc.