Isomaltooligosaccharides (IMOs) have good prebiotic effects, and long IMOs (LIMOs) with a degree of polymerization (DP) of 7 or above show improved effects. However, they are not yet commercially available, and require costly enzymes and processes for production. The Nterminal region of the thermostable Thermoanaerobacter thermocopriae cycloisomaltooligosaccharide glucanotransferase (TtCITase) shows cyclic isomaltooligosaccharide (CI)-producing activity owing to a catalytic domain of glycoside hydrolase (GH) family 66 and carbohydrate-binding module (CBM) 35. In the present study, we elucidated the activity of the C-terminal region of TtCITase (TtCITase-C; Met740-Phe1,559), including a CBM35-like region and the GH family 15 domain. The domain was successfully cloned, expressed, and purified as a single protein with a molecular mass of 115 kDa. TtCITase-C exhibited optimal activity at 40°C and pH 5.5, and retained 100% activity at pH 5.5 after 18-h incubation. TtCITase-C synthesized α-1,6 glucosyl products with over seven degrees of polymerization (DP) by an α-1,6 glucosyl transfer reaction from maltopentaose, isomaltopentaose, or commercialized maltodextrins as substrates. These results indicate that TtCITase-C could be used for the production of α-1,6 glucosyl oligosaccharides with over DP7 (LIMOs) in a more cost-effective manner, without requiring cyclodextran.

中文翻译：

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来自热嗜热厌氧杆菌的热稳定CITase的羧基末端区域具有产生长异麦芽低聚糖的能力。

异麦芽低聚糖（IMOs）具有良好的益生元效果，聚合度（DP）为7或更高的长IMOs（LIMOs）显示出更好的效果。但是，它们尚未在市场上买到，并且需要昂贵的酶和生产方法。耐高温嗜热厌氧杆菌的N末端区域由于糖苷水解酶（GH）家族66和碳水化合物结合模块（CBM）35的催化结构域，环异麦芽低聚糖葡糖基转移酶（TtCITase）显示出产生环状异麦芽低聚糖（CI）的活性。在本研究中，我们阐明了C- TtCITase的末端区域（TtCITase-C; Met740-Phe1,559），包括CBM35样区域和GH家族15结构域。该域已成功克隆，表达并纯化为分子量为115 kDa的单一蛋白质。TtCITase-C在40°C和pH 5.5时表现出最佳活性，并且在18小时孵育后在pH 5.5时保持100％活性。TtCITase-C通过以麦芽五糖，异麦芽五糖或商品化麦芽糖糊精为底物的α-1,6葡糖基转移反应合成了超过七个聚合度（DP）的α-1,6葡糖基产物。