Glycosylation is one of the most prevalent molecular modifications in nature. Single or multiple sugars can decorate a wide range of acceptors from proteins to lipids, cell wall glycans and small molecules, dramatically affecting their activity. Here, we discovered that by 'hijacking' an enzyme of the cellulose synthesis machinery involved in cell wall assembly, plants evolved cellulose synthase-like enzymes (Csls) and acquired the capacity to glucuronidate specialized metabolites, that is, triterpenoid saponins. Apparently, endoplasmic reticulum-membrane localization of Csls and of other pathway proteins was part of evolving a new glycosyltransferase function, as plant metabolite glycosyltransferases typically act in the cytosol. Discovery of glucuronic acid transferases across several plant orders uncovered the long-pursued enzymatic reaction in the production of a low-calorie sweetener from licorice roots. Our work opens the way for engineering potent saponins through microbial fermentation and plant-based systems.

中文翻译：

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植物类萜代谢是细胞壁生物合成机制的组成部分。

糖基化是自然界中最普遍的分子修饰之一。单个或多个糖可以修饰从蛋白质到脂质，细胞壁聚糖和小分子的各种受体，从而极大地影响其活性。在这里，我们发现通过“劫持”参与细胞壁组装的纤维素合成机器中的一种酶，植物进化出了纤维素合酶样酶（Csls），并获得了葡萄糖醛酸专门化代谢产物的能力，即三萜皂苷。显然，Csls和其他途径蛋白的内质网膜定位是进化新糖基转移酶功能的一部分，因为植物代谢物糖基转移酶通常在细胞质中起作用。在多个植物订单中发现葡萄糖醛酸转移酶发现了从甘草根中生产低热量甜味剂的长期追求的酶促反应。我们的工作为通过微生物发酵和基于植物的系统工程设计高效皂苷开辟了道路。