State Key Laboratory of Natural and Biomimetic Drugs & Key Laboratory of Molecular Cardiovascular Sciences of Ministry of Education, School of Pharmaceutical Sciences, Peking University, 38 Xueyuan Road, Beijing, 100191, China.
Department of Biochemistry and Biophysics &, Department of Integration of Chinese and Western Medicine, School of Basic Medical Sciences, Peking University, 38 Xueyuan Road, Beijing, 100191, China.
Angew Chem Int Ed Engl. 2019 Aug 12;58(33):11513-11520. doi: 10.1002/anie.201905505. Epub 2019 Jul 8.
Herein, the catalytic promiscuity of TcCGT1, a new C-glycosyltransferase (CGT) from the medicinal plant Trollius chinensis is explored. TcCGT1 could efficiently and regio-specifically catalyze the 8-C-glycosylation of 36 flavones and other flavonoids and could also catalyze the O-glycosylation of diverse phenolics. The crystal structure of TcCGT1 in complex with uridine diphosphate was determined at 1.85 Å resolution. Molecular docking revealed a new model for the catalytic mechanism of TcCGT1, which is initiated by the spontaneous deprotonation of the substrate. The spacious binding pocket explains the substrate promiscuity, and the binding pose of the substrate determines C- or O-glycosylation activity. Site-directed mutagenesis at two residues (I94E and G284K) switched C- to O-glycosylation. TcCGT1 is the first plant CGT with a crystal structure and the first flavone 8-C-glycosyltransferase described. This provides a basis for designing efficient glycosylation biocatalysts.
本文探索了来自药用植物翠雀（Trollius chinensis）的新型 C-糖基转移酶（CGT）TcCGT1 的催化混杂性。TcCGT1 可以高效且区域特异性地催化 36 种黄酮类化合物和其他类黄酮的 8-C-糖基化，还可以催化各种酚类化合物的 O-糖基化。在 1.85Å分辨率下测定了 TcCGT1 与尿苷二磷酸复合物的晶体结构。分子对接揭示了 TcCGT1 催化机制的新模型，该模型由底物的自发去质子化引发。宽敞的结合口袋解释了底物的混杂性，而底物的结合构象决定了 C-或 O-糖基化活性。两个残基（I94E 和 G284K）的定点突变将 C-糖基化转变为 O-糖基化。TcCGT1 是第一个具有晶体结构的植物 CGT，也是第一个被描述的黄酮类化合物 8-C-糖基转移酶。这为设计高效糖基化生物催化剂提供了基础。
