Bancal P, Henson C A, Gaudillère J P, Carpita N C
Institut National de la Recherche Agronomique, Centre de Mondésir, Clermont Ferrand, France.
Carbohydr Res. 1991 Sep 18;217:137-51. doi: 10.1016/0008-6215(91)84124-w.
A fructan exohydrolase selective for (2----1)-linked terminal fructosyl linkages, isolated from barley (Hordeum vulgare L. cv. Morex) stems and leaf sheaths, was used to elucidate the chemical structures of several oligomeric fructans extracted from liliaceous and graminaceous species. Products released by enzymic and mild acid hydrolysis were separated by reversed-phase high-performance liquid chromatography. Gas-liquid chromatography-mass spectrometry of partially methylated alditol acetates permitted unequivocal deduction of many linkage sequences, first of the hydrolysis products and then of the original oligomers. We found that bifurcose, a tetrasaccharide formed by addition of a fructosyl unit to O-6 of the central fructose residue of 1-kestose, was a central molecule in the generation of the branched, oligomeric fructans of wheat (Triticum aestivum L. cv. Fidel). These arise by the extension of both (2----1)- and (2----6)-linked chains from the bifurcose branch-point residue. Some of the (2----6)-linked units that slowly accumulate in oligomers may arise in vivo from selective hydrolysis, by fructan exohydrolases, of (2----1)-linked terminal units at branch point residues rather than by the action of (2----6)-specific synthases. Limited hydrolysis by specific exohydrolases in vitro coupled with separation of the oligomeric products constitutes an effective approach to the sequence analysis of complex oligosaccharides.
从大麦（Hordeum vulgare L. cv. Morex）茎和叶鞘中分离出的一种对（2→1）连接的末端果糖基键具有选择性的果聚糖外切酶，被用于阐明从百合科和禾本科植物中提取的几种低聚果聚糖的化学结构。通过反相高效液相色谱法分离酶解和温和酸水解释放的产物。部分甲基化糖醇乙酸酯的气-液色谱-质谱联用技术能够明确推断出许多连接序列，首先是水解产物的连接序列，然后是原始低聚物的连接序列。我们发现，双歧糖是一种由果糖基单元添加到1-蔗果三糖中心果糖残基的O-6位形成的四糖，它是小麦（Triticum aestivum L. cv. Fidel）分支低聚果聚糖生成过程中的核心分子。这些低聚果聚糖是通过双歧糖分支点残基上（2→1）和（2→6）连接的链的延伸而产生的。一些在低聚物中缓慢积累的（2→6）连接单元可能在体内是由果聚糖外切酶对分支点残基上（2→1）连接的末端单元进行选择性水解产生的，而不是由（2→6）特异性合成酶的作用产生的。体外特定外切酶的有限水解与低聚产物的分离相结合，构成了一种对复杂寡糖进行序列分析的有效方法。
