Song Kyoung-Ju, Nam Ho-Woo
Department of Parasitology and Catholic Institute of Parasitic Diseases, College of Medicine, Catholic University of Korea, Seoul 137-701, Korea.
Korean J Parasitol. 2003 Sep;41(3):165-9. doi: 10.3347/kjp.2003.41.3.165.
This study describes the characterization of 80 kDa protease showing gelationlytic property among three proteases in the excretory/secretory proteins (ESP) from Toxoplasma gondii. The protease activity was detected in the ESP but not in the somatic extract of RH tachyzoites. This protease was active only in the presence of calcium ion but not other divalent cationic ions such as Cu(2+), Zn(2+), Mg(2+), and Mn(2+), implying that Ca(2+) is critical factor for the activation of the protease. The 80 kDa protease was optimally active at pH 7.5. Its gelatinolytic activity was maximal at 37 degrees C, and significant level of enzyme activity of the protease remained after heat treatment at 56 degrees C for 30 min or 100 degrees 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. gondii was classified as a calcium dependent neutral metalloprotease.
本研究描述了在刚地弓形虫排泄/分泌蛋白（ESP）中的三种蛋白酶中，具有凝胶溶解特性的80 kDa蛋白酶的特性。在ESP中检测到蛋白酶活性，但在RH速殖子的体细胞提取物中未检测到。这种蛋白酶仅在钙离子存在时具有活性，而在其他二价阳离子如Cu(2+)、Zn(2+)、Mg(2+)和Mn(2+)存在时无活性，这意味着Ca(2+)是激活该蛋白酶的关键因素。80 kDa蛋白酶在pH 7.5时活性最佳。其凝胶溶解活性在37℃时最大，在56℃热处理30分钟或100℃热处理10分钟后，该蛋白酶仍保留显著水平的酶活性。这种耐热酶受到金属螯合剂（即EDTA、EGTA和1,10 - 菲咯啉）的强烈抑制。因此，刚地弓形虫分泌的ESP中的80 kDa蛋白酶被归类为钙依赖性中性金属蛋白酶。
