Discovery and biosynthetic investigations of NAD-derived natural products

天然产物及其衍生物作为药物开发的先导结构具有重要意义。它们是由特征性的生物合成酶产生的，这些酶转化特定的初级代谢产物并产生总的天然产物碳骨架。典型的天然产物类别的成员，如萜类化合物、聚酮化合物和非核糖体肽衍生自寡异戊二烯基二磷酸、活化的C2-结构单元如丙二酰辅酶A或氨基酸。除了这些经典的天然产物家族之外，最近显示中心电子载体烟酰胺腺嘌呤二核苷酸（NAD）充当结构独特的异亮氨酰-tRNA合成酶抑制剂的生物合成的构建块。生物信息学分析表明，新的NAD利用代谢途径对未知的NAD衍生的天然产物在自然界中编码。该项目的目标是NAD衍生的天然产物的鉴定和生物合成研究。为了实现这些目标，将开发和应用同位素引导的非靶向代谢组学方法。将合成13 C标记的生物合成前体并用于喂养实验，以选择性标记NAD衍生的代谢物。在一种互补的方法中，将建立一个异源生产平台，以实现沉默生物合成基因簇的产品鉴定。将分离新型NAD衍生代谢物，并基于抗性基因考虑（氨酰-tRNA合成酶抑制剂）确定其结构和生物学特性，重点关注抗生素活性。该项目的第二个目的是对选定的基因簇进行生物合成研究，重点是编码的PLP依赖酶的酶学。因此，该项目将有助于调查新发现的NAD衍生的天然产物类别，有可能发现新的抗感染药物，以及参与其生物合成的前所未有的酶化学。

Natural products and their derivatives have significance as lead structures for drug development. They are generated by characteristic biosynthetic enzymes, which convert specific primary metabolites and produce the overall natural product carbon backbones. Members of canonical natural product classes, such as terpenoids, polyketides and non-ribosomal peptides are derived from oligoprenyl diphosphates, activated C2-building blocks like malonyl-CoA or amino acids. Besides these classical natural product families, it was recently shown that the central electron carrier nicotinamide adenine dinucleotide (NAD) acts as a building block for the biosynthesis of structurally unique isoleucyl-tRNA synthetase inhibitors. Bioinformatic analyses suggests, that novel NAD-utilizing metabolic pathways towards yet unknown NAD-derived natural products are encoded in Nature. The project aim is the identification and biosynthetic investigation of NAD-derived natural products. To achieve these goals, an isotope-guided untargeted metabolomics methods will be developed and applied. 13C-labeled biosynthetic precursors will be synthesized and utilized for feeding experiments to enable selective labeling of NAD-derived metabolites. In a complementary approach, a heterologous production platform will be established to enable product identification of silent biosynthetic gene clusters. Novel NAD-derived metabolites will be isolated and their structural and biological properties determined with a focus on antibiotic activity, based on resistance gene considerations (aminoacyl-tRNA synthetase inhibitors). The second aim of the project is the biosynthetic investigation of a selected gene cluster, focusing on the enzymology of the encoded PLP-dependent enzyme. The project will thus contribute to the investigation of the newly discovered NAD-derived natural product class, with the potential to discover novel antiinfectives, as well as unprecedented enzyme chemistries involved in their biosynthesis.