Ferrer A, Hoebeke J, Bout D
CJF-INSERM 93-09, Equipe associèe INRA d'Immunologie Parasitaire, UFR des Sciences Pharmaceutiques, 31 Avenue Monge, Tours, 37200, France.
Exp Parasitol. 1999 May;92(1):64-72. doi: 10.1006/expr.1999.4404.
Two distinct alpha-amylases have been identified in Toxoplasma gondii. They were purified close to homogeneity from cytoplasmic and membrane fractions. The apparent molecular weight of the cytoplasmic amylase was 22,300 Da and that of the membrane enzyme was 39,600 Da by gel filtration, and 25,000 and 41,000 Da by SDS gel electrophoresis, respectively. The physicochemical and catalytic properties of both enzymes showed them to be very different. Cytoplasmic alpha-amylase had an acid isoelectric point and its optimum pH was pH 5.0; its activity was unaffected by NaCl, Ca2+, or EDTA. The membrane alpha-amylase had an isoelectric point of 7.7 and an optimum pH of 8.0. It was affected by Ca2+, inhibited by EDTA, and activated eight-fold by NaCl. Both amylases were inactivated by temperatures above 65 degrees C, but cytoplasmic amylase was more resistant to thermal denaturation.
在刚地弓形虫中已鉴定出两种不同的α淀粉酶。它们从细胞质和膜组分中纯化至接近均一状态。通过凝胶过滤，细胞质淀粉酶的表观分子量为22,300道尔顿，膜酶的表观分子量为39,600道尔顿；通过SDS凝胶电泳，分别为25,000和41,000道尔顿。两种酶的物理化学和催化特性显示它们非常不同。细胞质α淀粉酶具有酸性等电点，其最适pH为pH 5.0；其活性不受NaCl、Ca2+或EDTA的影响。膜α淀粉酶的等电点为7.7，最适pH为8.0。它受Ca2+影响，被EDTA抑制，并被NaCl激活8倍。两种淀粉酶在高于65摄氏度的温度下均失活，但细胞质淀粉酶对热变性更具抗性。
