农用抗生素-多氧霉素与马来亚霉素核苷骨架的比较生物合成研究

Polyoxin is a peptidyl nucleoside antibiotic with significant bioactivity against phytopathengenic fungi, as a result, it has been extensively used in agriculture. Malayamycin is also a nucleoside agro-antibiotic which highlights remarkable antifungal bioactivity and application potentials. Our previous studies have illustrated the mechanism for the biosynthesis of the intermediate-octosyl acid in polyoxin nucleoside skeleton pathway, to our surprise, malayamycin nucleoside skeleton is structurally similar to octosyl acid, while its biosynthetic gene cluster contains all of the essential genes which are correspondingly homologous to those required for the biosynthesis of polyoxin nucleoside skeleton, implicating that the enzymatic reactions in the biosynthetic pathways of polyoxin and malayamycin nucleoside skeletons are highly amazing and unusual, however, the mechanism for the biosynthesis of both nucleoside skeletons has long remained elusive. This study, with combination of bioinformatic, genetic, and biochemical approaches, aims to decipher the nucleoside skeleton biosynthetic pathways of polyoxin and malayamycin at molecular level, and to elucidate the mechanisms of the distinctive enzymatic reaction(s) governing the structural diversities of both nucleoside skeletons, thereof laying a foundation for future studies on the combinatorial biosynthesis of this group of antibiotics.

多氧霉素(Polyoxin)为肽核苷类抗生素，由于其抗植物病原真菌活性显著，故在农业上广泛使用；马来亚霉素(Malayamycin)则是具有良好抗真菌生物活性及应用潜力的核苷类农用抗生素。本课题组前期研究揭示了多氧霉素核苷骨架中间代谢产物-庚糖酸的生物合成机理，令人惊奇的是，马来亚霉素核苷骨架与庚糖酸结构相似，但其生物合成基因簇中含有多氧霉素核苷骨架生物合成所必需的全部同源基因，由此暗示多氧霉素和马来亚霉素核苷骨架生物合成途径中拥有新奇的酶促反应；然而迄今为止，二者核苷骨架的生物合成机理一直悬而未决。本研究旨在综合生物信息学、遗传学和生物化学手段，从分子水平上解析多氧霉素和马来亚霉素核苷骨架的生物合成途径，同时破解调控二者核苷骨架结构差异的独特酶促反应机制，进而为今后该类抗生素的组合生物合成研究奠定基础。

多氧霉素(Polyoxin)为肽核苷类抗生素，由于其抗植物病原真菌活性显著，故在农业上广泛使用；马来亚霉素(Malayamycin)则是具有良好抗真菌生物活性及应用潜力的核苷类农用抗生素。本项目研究通过综合多学科研究手段，克隆了马来亚霉素的生物合成基因簇，解析了多氧霉素与马来亚霉素核苷骨架的生物合成途径，阐明了多氧霉素核苷骨架与肽基模块氨甲酰多氧草胺酸组装的酶促反应机理，进而从分子水平上揭示了多氧霉素与马来亚霉素核苷骨架的生物合成机理。此外，项目组通过与本团队结构生物学课题组合作，解析了假尿苷合成酶MalM(TruD)的晶体结构，并实现了假尿苷在大肠杆菌中的工程化产生；值得一提的是，本项目组成功改造多氧霉素工业菌株为细胞工厂，利用合成生物学策略，人工设计并合成了多个个结构新颖，活性显著的杂合抗生素，另外，本研究的相关成果已在合作企业得到产业化应用。与此同时，在本项目的支持下，项目组在相关核苷类抗生素的生物合成与合成生物学研究方面也获得可喜进展，从而为今后核苷类抗生素的应用基础研究奠定了坚实的基础。