Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark.
Chr. Hansen A/S, Bøge Alle 10-12, 2970, Hørsholm, Denmark.
Nat Commun. 2017 Dec 7;8(1):1987. doi: 10.1038/s41467-017-02031-z.
Carminic acid, a glucosylated anthraquinone found in scale insects like Dactylopius coccus, has since ancient times been used as a red colorant in various applications. Here we show that a membrane-bound C-glucosyltransferase, isolated from D. coccus and designated DcUGT2, catalyzes the glucosylation of flavokermesic acid and kermesic acid into their respective C-glucosides dcII and carminic acid. DcUGT2 is predicted to be a type I integral endoplasmic reticulum (ER) membrane protein, containing a cleavable N-terminal signal peptide and a C-terminal transmembrane helix that anchors the protein to the ER, followed by a short cytoplasmic tail. DcUGT2 is found to be heavily glycosylated. Truncated DcUGT2 proteins synthesized in yeast indicate the presence of an internal ER-targeting signal. The cleavable N-terminal signal peptide is shown to be essential for the activity of DcUGT2, whereas the transmembrane helix/cytoplasmic domains, although important, are not crucial for its catalytic function.
胭脂红酸是一种葡萄糖基蒽醌，存在于胭脂虫等介壳虫中，自古以来就被用作各种应用的红色着色剂。在这里，我们展示了一种从胭脂虫中分离出来的膜结合 C-葡萄糖基转移酶，命名为 DcUGT2，它催化了法呢基奎宁酸和胭脂酸分别向其相应的 C-葡萄糖苷 dcII 和胭脂酸的葡萄糖基化。DcUGT2 预测为一种 I 型内质网（ER）膜蛋白，包含一个可切割的 N 端信号肽和一个将蛋白锚定在 ER 上的 C 端跨膜螺旋，后面跟着一个短的细胞质尾巴。发现 DcUGT2 高度糖基化。在酵母中合成的截断的 DcUGT2 蛋白表明存在内部 ER 靶向信号。可切割的 N 端信号肽对于 DcUGT2 的活性是必需的，而跨膜螺旋/细胞质结构域虽然很重要，但对于其催化功能不是关键的。
