### O-GlcNAc转移酶及其抑制剂

1. 中国科学院大学化学与化工学院 北京 100049
• 投稿日期:2013-05-17 发布日期:2013-07-19
• 通讯作者: 王玥 E-mail:yuewang@ucas.ac.cn
• 作者简介:王玥博士1985 年出生于辽宁省, 2006 年在北京大学药学院获得学士学位, 2006 年到2012 年在北京大学天然药物及仿生药物国家重点实验室叶新山教授课题组攻读硕士和博士学位, 此后加入中国科学院大学化学与化工学院, 主要研究方向为糖化学生物学和糖类药物的发现.

### O-GlcNAc Transferase and Its Inhibitors

Wang Yue

1. School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences, Beijing 100049
• Received:2013-05-17 Published:2013-07-19

O-GlcNAc转移酶(OGT)是一种哺乳动物必需的酶, 其将单个的N-乙酰氨基葡萄糖(GlcNAc)以β-构型的O-糖苷键连接到蛋白质的丝氨酸和苏氨酸(Ser/Thr)羟基上. O-GlcNAc糖基化在细胞质和细胞核中广泛地存在, 这种蛋白质的翻译后修饰对细胞内的许多信号通路具有调节作用, 并与多种重大疾病的发生和发展密切相关. 本文主要对OGT的结构、催化机制、活性测定方法和抑制剂的研究现状进行综述, 并对研究前景进行展望.

O-GlcNAc transferase (OGT), one of essential mammalian enzymes, catalyses the transfer of N-acetylglucos- amine from UDP-N-acetylglucosamine (UDP-GlcNAc) to hydroxyl groups of serines and threonines (Ser/Thr) in proteins. O-GlcNAcylation is widely located in cytoplasm and nucleus. This kind of protein post-translational modification is involved in the regulation of many cellular signaling pathways and closely associated with the occurrences and developments of numerous critical illnesses. In animals, OGT is encoded by a single highly conserved gene. However, human OGT includes three different isoforms at least: nucleocytoplasmic OGT (ncOGT), mitochondrial OGT (mOGT) and short OGT (sOGT). All of the isoforms comprise two distinct regions: a multidomain catalytic region and an N-terminal region with different numbers of tetratricopeptide repeats (TPRs), which is closely related to their subcellular localizations. The structures of the catalytic region and TPRs were reported and it was supported that OGT uses an ordered sequential "bi-bi" mechanism though the details of catalytic mechanism were not completely understood. To discover the inhibitors of OGT, several OGT activity assay methods were developed. The conventional method uses a radiolabeled glycosyl donor substrate such as UDP-[3H]-GlcNAc or UDP-[14C]-GlcNAc so that it is not suitable for in vivo test or rapid analysis. O-GlcNAc antibody-based western blot was performed to measure the activity of OGT in vivo, but it is infeasible to determine low abundance protein with single O-GlcNAc. Three high throughput activity assays were reported: ligand displacement OGT assay, protease-protection assay strategy and azido-enzyme-linked immunosorbent assay (azido-ELISA). The first two methods have especially been used to find new OGT inhibitors through screening compound libraries, but the results have to be verified by the conventional method. To date, OGT inhibitor activity of several candidates was evaluated and as found, two of them {2-acetamido-1,3,4,6-tetra-O-acetyl-2-deoxy-5-thio-α-D-glucopyranose and 4-methoxyphenyl 6-acetyl-2-oxobenzo[d]-oxazole-3(2H)-carboxylate} worked effectively in vivo and were valuable for understanding the functional roles of OGT. Nevertheless, there are still important questions to be answered in the research of OGT: (1) What is the general base that catalyzes O-GlcNAcylation reaction? (2) How can OGT recognize so many protein substances with the preservation of substance specificity? (3) How can we develop robust high-throughput OGT assays and isoform-specific OGT inhibitors? In conclusion, there is a long way to go for comprehensive understanding of OGT.