n nnnFlavonoids are most commonly conjugated with various sugar moietiesby UDP-sugar:glycosyltransferases (UGTs) in a lineage-specificmanner. Generally, the phylogenetics and regiospecificity offlavonoid UGTs are correlated, indicating that the regiospecificityof UGT differentiated prior to speciation. By contrast, it isunclear how the sugar donor specificity of UGTs evolved. Here,we report the biochemical, homology-modeled, and phylogeneticcharacterization of flavonoid 7-O-glucuronosyltransferases (F7GAT),which is responsible for producing specialized metabolites inLamiales plants. All of the Lamiales F7GATs were found to bemembers of the UGT88-related cluster and specifically used UDP-glucuronicacid (UDPGA). We identified an Arg residue that is specificallyconserved in the PSPG box in the Lamiales F7GATs. Substitutionof this Arg with Trp was sufficient to convert the sugar donorspecificity of the Lamiales F7GATs from UDPGA to UDP-glucose.Homology modeling of the Lamiales F7GAT suggested that the Argresidue plays a critical role in the specific recognition ofanionic carboxylate of the glucuronic acid moiety of UDPGA withits cationic guanidinium moiety. These results support the hypothesisthat differentiation of sugar donor specificity of UGTs occurredlocally, in specific plant lineages, after establishment ofgeneral regiospecificity for the sugar acceptor. Thus, the plasticityof sugar donor specificity explains, in part, the extraordinarystructural diversification of phytochemicals.展开▼
机译：ABSTRACTn n
n TOP n <字体颜色= 464c53>抽象 n 介绍 n 结果 n 讨论 n 方法 n 参考文献 n n nnn类黄酮通常与各种糖部分缀合 通过UDP-糖：糖基转移酶（UGT）以谱系特异性 方式进行修饰。通常， 类黄酮UGT的系统发育和区域特异性是相关的，表明UGT的区域特异性 在物种形成之前就已经分化。相比之下， 尚不清楚UGT的糖供体特异性如何进化。在这里， 我们报告了类黄酮7- O -葡萄糖醛酸糖基转移酶（F7GAT）， < / SUP>负责在 拉马莱斯植物中产生专门的代谢产物。发现所有拉米亚莱斯F7GAT都是与UGT88相关的簇的 成员，并且专门使用了UDP-葡萄糖醛酸 酸（UDPGA）。我们鉴定了在Lamiales F7GATs的PSPG盒中特别 保守的Arg残基。用Trp替代此Arg的 足以将Lamiales F7GAT的糖供体 特异性从UDPGA转换为UDP-葡萄糖。 Lamiales F7GAT认为Arg 残基在特异性识别UDPGA的葡糖醛酸部分具有 阳离子胍基的 阴离子羧酸盐中起关键作用部分。这些结果支持以下假设 ：在特定植物谱系中，对糖建立 的一般区域特异性后，UGT的糖供体特异性的分化发生在局部 受体。因此，糖供体特异性的可塑性 可以部分解释植物化学物质非同寻常的 结构多样化。展开▼
