Fauré Régis, Saura-Valls Marc, Brumer Harry, Planas Antoni, Cottaz Sylvain, Driguez Hugues
Centre de Recherche sur les Macromolécules Végétales (CERMAV-CNRS), BP53, 38041 Grenoble Cedex 9, France.
J Org Chem. 2006 Jul 7;71(14):5151-61. doi: 10.1021/jo0525682.
Complex oligosaccharides containing alpha-D-xylosyl-(1-->6)-beta-D-glucosyl residues and unsubstituted beta-(1-->4)-linked D-glucosyl units were readily synthesized using enzymatic coupling catalyzed by the Cel7B E197A glycosynthase from Humicola insolens. Constituting this library required four key steps: (1) preparing unprotected building blocks by chemical synthesis or enzymatic degradation of xyloglucan polymers; (2) generating the donor synthon in the enzymatic coupling by temporarily introducing a lactosyl motif on the 4-OH of the terminal glucosyl units of the xylogluco-oligosaccharides; (3) synthesizing the corresponding alpha-fluorides, followed by their de-O-acetylation and the glycosynthase-catalyzed condensation of these donors onto various acceptors; and (4) enzymatically releasing lactose or galactose from the reaction product, affording the target molecules in good overall yields. These complex oligosaccharides proved useful for mapping the active site of a key enzyme in plant cell wall biosynthesis and modification: the xyloglucan endo-transglycosylase (XET). We also report some preliminary enzymatic results regarding the efficiency of these compounds.
利用来自特异腐质霉的Cel7B E197A糖基合成酶催化的酶促偶联反应，可轻松合成含有α-D-木糖基-(1→6)-β-D-葡萄糖基残基和未取代的β-(1→4)-连接的D-葡萄糖基单元的复杂寡糖。构建该文库需要四个关键步骤：(1) 通过木葡聚糖聚合物的化学合成或酶促降解制备未保护的构建模块；(2) 通过在木葡寡糖末端葡萄糖基单元的4-OH上暂时引入乳糖基基序，在酶促偶联反应中生成供体合成子；(3) 合成相应的α-氟化物，然后进行脱O-乙酰化，并将这些供体在糖基合成酶催化下缩合到各种受体上；(4) 从反应产物中酶促释放乳糖或半乳糖，以较高的总收率得到目标分子。这些复杂寡糖被证明可用于绘制植物细胞壁生物合成和修饰中的一种关键酶——木葡聚糖内转糖基酶（XET）的活性位点。我们还报告了关于这些化合物效率的一些初步酶促结果。
