阿维菌素中L-齐墩果糖的生物合成机制研究

Avermectins, produced by Streptomyces avermectins, are a group of macrolactone antibiotics with remarkable insecticidal activity and have been widely used in aveterinary and medicinal fields. An unusual sugar appendage contains two L-oleandroses presents in all eight avermectins and is found very important for their bioactivities. Unfortunately, the biosynthesis mechanism of L-oleandrose in avermectin remains elusive. In this project, we will overexpress and purify four important proteins, AvrE, AvrF, AvrH, and AvrI, which are involved in the late biosynthetic steps of L-oleandrose. We will also prepare the substrates and product standards by bioassays and chemical synthesis. Finally, we will elucidate the functions of all these proteins and propose a detailed biosynthesis pathway of L-oleandrose in avermectin, which will lay a solid foundation for further combinatorial biosynthesis and synthetic biological studies of avermectin.

阿维菌素是由阿维链霉菌产生的一种具有杀虫活性的大环内酯类抗生素，广泛应用于畜牧业和医药行业中。它的结构中特殊的L-齐墩果糖二糖结构对阿维菌素的生物活性有显著影响，但对于阿维菌素中L-齐墩果糖的生物合成机制还有一些未阐明的问题。本课题将通过体外酶学的研究手段对L-齐墩果糖生物合成中四个重要蛋白(AvrE, AvrF, AvrH, AvrI)的功能进行研究，清晰地阐释阿维菌素中L-齐墩果糖的生物合成途径，为通过组合生物合成和合成生物学得到新结构的阿维菌素类药物分子打下基础。

阿维菌素是八元大环内酯类抗生素，结构中含有的特殊的L-齐墩果糖二糖对阿维菌素的杀虫活性有显著影响。本课题通过体外酶学的研究手段对L-齐墩果糖生物合成中三个重要蛋白AvrI, AvrF和 AvrH的功能进行研究，验证了它们的功能分别是TDP-3,4-二酮-2,6-二脱氧-D-葡萄糖-3-酮基还原酶，TDP-2,6-二脱氧-4-酮-D-阿洛糖-5-异构酶，TDP-L-橄榄糖-3-氧甲基转移酶。基于以上的生物合成过程，我们成功的在大肠杆菌中重构了TDP-L-齐墩果糖的途径。该课题补全了阿维菌素的生物合成途径，并且为之后研究提供了坚实的基础。