Protease activity of 80 kDa protein secreted from the apicomplexan parasite Toxoplasma gondii

Abstract

This study describes the characterization of 80 kDa protease showing gelationlytic property among threeproteases in the excretory/secretory proteins (ESP) from Toxoplasma gondii . The protease activity was detected inthe ESP but not in the somatic extract of RH tachyzoites. This protease was active only in the presence of calcium ionbut not other divalent cationic ions such as Cu2+, Zn2+, Mg2+, and Mn2+, implying that Ca2+ is critical factor for theactivation of the protease. The 80 kDa protease was optimally active at pH 7.5. Its gelatinolytic activity was maximalat 37?C, and significant level of enzyme activity of the protease remained after heat treatment at 56?C for 30 min or100?C for 10 min. This thermostable enzyme was strongly inhibited by metal chelators, i.e., EDTA, EGTA, and 1,10-phenanthroline. Thus, the 80 kDa protease in the ESP secreted by T. gondiiwas classified as a calcium dependent neutral metalloprotease.