Abstract A low molecular weight intracellular and extracellular fructosyltransferase was purified from the wild (Wt) and improved mutant-type (Mt) Aureobasidium pullulans and its characteristics and thermodynamic properties determined. The Wt had been previously genetically modified by chemical mutagenesis. The purified fructosyltransferases from the Wt and Mt had subunit molecular weights between 13.4 and 17.0 kDa, respectively. The pH of the purified fructosyltransferase from the Wt and Mt were within 4.0–5.5. From the KM values, the fructosyltransferase from Mt showed higher affinity for sucrose than Wt fructosyltransferase. The optimum temperature obtained for the Mt intracellular and extracellular fructosyltransferase were 80 and 70 °C, respectively, while the Wt extracellular and intracellular fructosyltransferase was 60 °C. Most metals enhanced fructosyltransferase activity in a concentration-dependent manner except for mercury. Triton X-100 and Tween-80 enhanced the fructosyltransferase activity. Organic solvents such as acetone, ethanol, methanol, toluene and dichloromethane enhanced the enzyme activity while dimethylformamide inhibited the enzyme. From the thermodynamic and kinetic parameters ( Mt fructosyltransferase was more stable to thermal inactivation than the Wt fructosyltransferase. Hence, it can be concluded that, after strain improvement of the Wt, the purified Mt fructosyltransferase was more stable to organic solvents, surfactants, and thermal denaturation, etc. compared to the Wt. This makes Mt fructosyltransferase more useful mostly in the food industry than the Wt.

中文翻译：

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来自野生和改良突变型 Aureobasidium pullulans NAC8 的纯化果糖基转移酶的一些生化、催化、热力学和动力学特性

摘要 从野生（Wt）和改良的突变型（Mt）出芽短梗霉中纯化了一种低分子量的胞内和胞外果糖基转移酶，并确定了其特性和热力学性质。Wt 先前已通过化学诱变进行了遗传修饰。来自 Wt 和 Mt 的纯化果糖基转移酶的亚基分子量分别在 13.4 和 17.0 kDa 之间。来自 Wt 和 Mt 的纯化果糖基转移酶的 pH 值在 4.0-5.5 之间。从 KM 值来看，来自 Mt 的果糖基转移酶对蔗糖的亲和力高于 Wt 果糖基转移酶。Mt 胞内和胞外果糖基转移酶的最适温度分别为 80 和 70 °C，而 Wt 胞外和胞内果糖基转移酶的最适温度为 60 °C。除汞外，大多数金属以浓度依赖性方式增强果糖基转移酶活性。Triton X-100 和 Tween-80 增强了果糖基转移酶的活性。有机溶剂如丙酮、乙醇、甲醇、甲苯和二氯甲烷增强酶活性，而二甲基甲酰胺抑制酶活性。从热力学和动力学参数（ Mt 果糖基转移酶比 Wt 果糖基转移酶对热失活更稳定。因此，可以得出结论，经过 Wt 的菌株改进，纯化后的 Mt 果糖基转移酶对有机溶剂、表面活性剂和热失活更稳定。与 Wt 相比，变性等。这使得 Mt 果糖基转移酶在食品工业中比 Wt 更有用。