【摘要】 从污染的右旋糖酐溶液中分离出一株外切异麦芽三糖水解酶（Exo-isomaltotrio-hydrolase,1,6-α-D-Glucan isomaltotriohydrolase EC 3.2.1.95）产生菌,经鉴定为产碱菌（Alcaligenes sp.）.研究了酶的产生条件和基本性质.产酶最适培养基组成（%）:右旋糖酐1.5、鱼粉蛋白胨1、酵母抽提物0.1、牛肉膏0.3、甲醇2,pH8.0,250ml三角瓶中装20ml培养基,于26℃200r/min旋转摇床上振荡培养48小时.酶的最适作用温度和pH分别为50℃和p H6.5—7.5,在pH5.0—10.6范围内稳定.在40℃保温24小时酶活力基本不变,50℃保温8小时剩余酶活力为71.8%,保温24小时剩余酶活力为44.2%,在55℃酶活力的半寿期为10 小时.金属离子Hg²⁺、Ag⁺对酶强烈抑制.水解右旋糖酐的终产物为异麦芽三糖,酶的作用方式为外切型.更多还原

【Abstract】 An extracellular exo-isomaltotriohydrolase (1, 6-α-D-Glucan isomaltotrio-hydrolase EC 3. 2. 1. 95) was obtained from culture broth of a dextran-degrading mi-crooganism, which had been isolated from contaminated dextran solution and was identified as Alcaligenes sp. The formation conditions and some properties of the enzyme were studied. Maximal isomaltotriohydrolase formation was obtained when the strain was aer-obically grown at 26℃ for 48 h in a medium containing 1. 5% dextran,1% fish peptone, 0. 1% yeast extract,0. 3% beef extract,2% methanol and trace amunts of inorganic salt, pH 8. 0. The enzyme had an optimal pH of 6. 5-7. 5 and an optimal temperature of 50-55℃. The enzyme was quite stable over the range of pH5. 0-10. 6 and a temperature lower than 40℃. Residual activity was nearly 100% after incubated at 40℃ for 24 h. The Half-life of enzyme activity was 10 h at 55℃. The enzyme was inhibited by Hg2+and Ag+. Isomaltotriose was the only digestion product of dextran. The result suggested that the enzyme is an exo-type dextranase,i. e. an isomaltotriohydrolase.更多还原