抗肿瘤BIQ聚酮榴菌素生物合成中独特的糖基化机制研究

榴菌素能特异地抑制Cdc7激酶、FTase、IMPDH等的活性，是BIQ中最具潜力的临床抗癌候选药物。其生物合成存在非常独特糖基化过程：橄榄糖通过两个C-C单键与受体连接生成榴菌素A，另一个玫红糖通过O-C糖苷键接在橄榄糖上形成榴菌素B。C-糖基化是一种少见的后修饰方式，而糖基与受体通过两个C-C单键相连的目前仅此一例，更让人迷惑的是其基因簇内仅有一个糖基转移酶基因。因此榴菌素的糖基化过程是值得深入研究的科学问题。前期我们发现了一株可有效遗传操作的榴菌素产生菌，并测定了该菌的全基因组序列。本项目在此基础上，利用基因敲除、定点突变、生物转化、体外酶促反应等手段开展研究，旨在明确参与该糖基化过程的糖基转移酶，找到影响其催化活性的关键位点，阐明两个C-C单键形成的基本过程和决定因素，初步揭示该酶所蕴含的独特催化机制，从而为在组合生物合成中利用该酶创造新的活性物质或提高现有化合物的药效等奠定基础。

Granaticin can specifically inhibit Cdc7 kinase , FTase and IMPDH. As such, it is the most potential clinical anticancer drug candidate amongst the BIQ members. During its biosynthesis, a very unique biosynthetic glycosylation processes was found: Olivose sugar attached to the BIQ algycone through two C-C bonds forming granaticin A, another rhodinose sugar connecting with the olivose sugar moiety by an O-C glycoside bond. C-glycosylation is a rare post-modification pattern, and sugar-receptor linked via two C-C bonds currently was only found in this case. More confusing is the only one glycosyltransferase gene existing in the granaticin biosynthetic gene cluster. So the glycosylation of granaticin is a scientific issue worthy of further study. We previously found a genetic manipulable granaticin producing strain, and determined the whole genome sequence of it. On these bases, by the use of gene knockout , site-directed mutagenesis, biotransformation and in vitro enzymatic reaction , this project aims to specify the glycosyltransferase(s) involved in the granaticin glycosylation process , to find the key active sites with decisive influence on its catalytic activity, to illustrate the two C-C bonds forming process, and to preliminary reveal the unique catalytic mechanism inside, thereby paving the way to creat new bioactive substances by using this unique glycosyltransferase in a combinational biosynthesis strategy.