te Poele Evelien M, Grijpstra Pieter, van Leeuwen Sander S, Dijkhuizen Lubbert
Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen , Nijenborgh 7, 9747 AG Groningen, The Netherlands.
Bioconjug Chem. 2016 Apr 20;27(4):937-46. doi: 10.1021/acs.bioconjchem.6b00018. Epub 2016 Mar 8.
Lactic acid bacteria use glucansucrase enzymes for synthesis of gluco-oligosaccharides and polysaccharides (α-glucans) from sucrose. Depending on the glucansucrase enzyme, specific α-glucosidic linkages are introduced. GTFA-ΔN (N-terminally truncated glucosyltransferase A) is a glucansucrase enzyme of Lactobacillus reuteri 121 that synthesizes the reuteran polysaccharide with (α1 → 4) and (α1 → 6) glycosidic linkages. Glucansucrases also catalyze glucosylation of various alternative acceptor substrates. At present it is unclear whether the linkage specificity of these enzymes is the same in oligo/polysaccharide synthesis and in glucosylation of alternative acceptor substrates. Our results show that GTFA-ΔN glucosylates catechol into products with up to at least 5 glucosyl units attached. These catechol glucosides were isolated and structurally characterized using 1D/2D (1)H NMR spectroscopy. They contained 1 to 5 glucose units with different (α1 → 4) and (α1 → 6) glycosidic linkage combinations. Interestingly, a branched catechol glucoside was also formed along with a catechol glucoside with 2 successive (α1 → 6) glycosidic linkages, products that are absent when only sucrose is used as both glycosyl donor and acceptor substrate.
乳酸菌利用葡聚糖蔗糖酶从蔗糖合成低聚葡萄糖和多糖（α-葡聚糖）。根据葡聚糖蔗糖酶的不同，会引入特定的α-糖苷键。GTFA-ΔN（N端截短的葡糖基转移酶A）是罗伊氏乳杆菌121的一种葡聚糖蔗糖酶，它能合成具有（α1→4）和（α1→6）糖苷键的罗伊多糖。葡聚糖蔗糖酶还能催化各种替代受体底物的糖基化反应。目前尚不清楚这些酶在低聚糖/多糖合成以及替代受体底物糖基化过程中的键特异性是否相同。我们的结果表明，GTFA-ΔN能将儿茶酚糖基化为连接有至少5个葡糖基单元的产物。这些儿茶酚糖苷通过一维/二维（1）H核磁共振光谱进行分离和结构表征。它们含有1至5个葡萄糖单元，具有不同的（α1→4）和（α1→6）糖苷键组合。有趣的是，还形成了一种支链儿茶酚糖苷以及一种具有两个连续（α1→6）糖苷键的儿茶酚糖苷，而当仅使用蔗糖作为糖基供体和受体底物时，这些产物是不存在的。
