Functional and Structural Characterization of a Flavonoid Glucoside 1,6-Glucosyltransferase from Catharanthus roseus
Functional and Structural Characterization of a Flavonoid Glucoside 1,6-Glucosyltransferase from Catharanthus roseus
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DOI：
10.1093/pcp/pcp088
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发表时间：
2009-08-01
影响因子：
4.9
通讯作者：
Mizukami, Hajime
中科院分区：
文献类型：
--
作者：
Masada, Sayaka;Terasaka, Kazuyoshi;Mizukami, Hajime
糖基转移酶在高等植物小分子糖苷结构多样性中起着重要作用。首次从长春花中分离到一个糖糖葡萄糖基转移酶（CaUGT3）的cDNA克隆，该酶可催化黄酮醇和黄酮类糖苷的1,6-糖基化。CaUGT3表现出独特的糖基链延伸活性，不仅形成龙胆皂苷，而且顺序形成龙胆三苷和龙胆四苷。我们利用同源性建模和定点诱变研究了CaUGT3的功能特性，并确定了位于受体结合口袋中的氨基酸对于提供足够的空间容纳类黄酮糖苷而不是类黄酮苷元至关重要。这些结果为理解和设计糖基转移酶在植物糖苷生物合成中的催化作用提供了基础信息。
Sugarsugar glycosyltransferases play an important role in structural diversity of small molecule glycosides in higher plants. We isolated a cDNA clone encoding a sugarsugar glucosyltransferase (CaUGT3) catalyzing 1,6-glucosylation of flavonol and flavone glucosides for the first time from Catharanthus roseus. CaUGT3 exhibited a unique glucosyl chain elongation activity forming not only gentiobioside but also gentiotrioside and gentiotetroside in a sequential manner. We investigated the functional properties of CaUGT3 using homology modeling and site-directed mutagenesis, and identified amino acids positioned in the acceptor-binding pocket as crucial for providing enough space to accommodate flavonoid glucosides instead of flavonoid aglycones. These results provide basic information for understanding and engineering the catalytic functions of sugarsugar glycosyltransferases involved in biosynthesis of plant glycosides.