Qin Zhen, Yang Shaoqing, Zhao Liming, You Xin, Yan Qiaojuan, Jiang Zhengqiang
From the Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China; the School of Biotechnology, State Key Laboratory of Bioreactor Engineering, Research and Development Center of Separation and Extraction Technology in Fermentation Industry, East China University of Science and Technology, Shanghai 200237, China.
From the Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing 100083, China.
J Biol Chem. 2017 Feb 3;292(5):1666-1678. doi: 10.1074/jbc.M116.762419. Epub 2016 Dec 12.
Carbohydrates are complex macromolecules in biological metabolism. Enzymatic synthesis of carbohydrates is recognized as a powerful tool to overcome the problems associated with large scale synthesis of carbohydrates. Novel enzymes with significant transglycosylation ability are still in great demand in glycobiology studies. Here we report a novel glycoside hydrolase family 16 "elongating" β-transglycosylase from Paecilomyces thermophila (PtBgt16A), which efficiently catalyzes the synthesis of higher polymeric oligosaccharides using β-1,3/1,4-oligosaccharides as donor/acceptor substrates. Further structural information reveals that PtBgt16A has a binding pocket around the -1 subsite. The catalytic mechanism of PtBgt16A is partly similar to an exo-glycoside hydrolase, which cleaves the substrate from the non-reducing end one by one. However, PtBgt16A releases the reducing end product and uses the remainder glucosyl as a transglycosylation donor. This catalytic mechanism has similarity with the catalytic mode of amylosucrase, which catalyzes the transglycosylation products gradually extend by one glucose unit. PtBgt16A thus has the potential to be a tool enzyme for the enzymatic synthesis of new β-oligosaccharides and glycoconjugates.
碳水化合物是生物代谢中的复杂大分子。碳水化合物的酶促合成被认为是克服与碳水化合物大规模合成相关问题的有力工具。在糖生物学研究中，对具有显著转糖基化能力的新型酶仍有巨大需求。在此，我们报道了一种来自嗜热拟青霉的新型糖苷水解酶家族16“延伸型”β - 转糖基酶（PtBgt16A），它能以β - 1,3/1,4 - 寡糖作为供体/受体底物，高效催化合成更高聚合度的寡糖。进一步的结构信息表明，PtBgt16A在 - 1亚位点周围有一个结合口袋。PtBgt16A的催化机制部分类似于外切糖苷水解酶，即从非还原端逐个切割底物。然而，PtBgt16A释放出还原端产物，并将剩余的葡萄糖基用作转糖基化供体。这种催化机制与淀粉酶蔗糖酶的催化模式相似，淀粉酶蔗糖酶催化转糖基化产物逐渐逐个葡萄糖单位地延伸。因此，PtBgt16A有潜力成为用于酶促合成新型β - 寡糖和糖缀合物的工具酶。
