A novel α-d-galactosynthase from Thermotoga maritima converts β-d-galactopyranosyl azide to α-galacto-oligosaccharides
作者:Beatrice Cobucci-Ponzano、Carmela Zorzetti、Andrea Strazzulli、Sara Carillo、Emiliano Bedini、Maria Michela Corsaro、Donald A Comfort、Robert M Kelly、Mosè Rossi、Marco Moracci
DOI:10.1093/glycob/cwq177
日期:2011.4
The large-scale production of oligosaccharides is a daunting task, hampering the study of the role of glycans in vivo and the testing of the efficacy of novel glycan-based drugs. Glycosynthases, mutated glycosidases that synthesize oligosaccharides in high yields, are becoming important chemo-enzymatic tools for the production of oligosaccharides. However, while β-glycosynthase can be produced with a rather well-established technology, examples of α-glycosynthases are thus far limited only to enzymes from glycoside hydrolase 29 (GH29), GH31 and GH95 families. α-l-Fucosynthases from GH29 use convenient glycosyl azide derivatives as a strategic alternative to glycosyl fluoride donors. However, the general applicability of this method to other α-glycosynthases is not trivial and remains to be confirmed. Here, β-d-galactopyranosyl azide was converted to α-galacto-oligosaccharides with good yields and high regioselectivity, catalyzed by a novel α-galactosynthase based on the GH36 α-galactosidase from the hyperthermophilic bacterium Thermotoga maritima. These results open a new avenue to the practical synthesis of biologically interesting α-galacto-oligosaccharides and demonstrate more widespread use of β-glycosyl-azide as donors, confirming their utility to expand the repertoire of glycosynthases.
寡糖的大规模生产是一项艰巨的任务,阻碍了聚糖在体内作用的研究和新型聚糖药物功效的测试。糖合酶是高产合成寡糖的突变糖苷酶,正在成为寡糖生产的重要化学酶工具。然而,虽然 β-糖合酶可以通过相当成熟的技术生产,但 α-糖合酶的例子迄今为止仅限于来自糖苷水解酶 29 (GH29)、GH31 和 GH95 家族的酶。 GH29 的 α-l-岩藻糖合成酶使用方便的糖基叠氮衍生物作为糖基氟化物供体的战略替代品。然而,该方法对其他 α-糖合酶的普遍适用性并非微不足道,仍有待证实。在这里,β-d-吡喃半乳糖基叠氮化物被一种新型 α-半乳糖合酶催化,以良好的产率和高区域选择性转化为 α-低聚半乳糖,该酶基于来自超嗜热细菌海栖热袍菌的 GH36 α-半乳糖苷酶。这些结果为实际合成具有生物学意义的α-低聚半乳糖开辟了一条新途径,并证明了β-糖基叠氮化物作为供体的更广泛用途,证实了它们在扩展糖合酶库方面的效用。