Structure and biosynthesis of unusual polyamine and polyagmatine natural products

光杆状菌属和黄杆状菌属的昆虫病原细菌已被证明是新型天然产物的丰富来源。然而，它们的结构和生物合成通常仍然未知。因此，本项目将详细研究两种结构非常不寻常的天然产物的生物合成：1。与玉米胺相似的多胺天然产物。玉米胺只是具有广泛抗菌活性的高度不寻常的天然产物类别的三个已知成员之一。它是具有额外胺取代基的线性长链胺（长度>30个碳原子）。生物化学上，这种不寻常的结构可能来自于与多不饱和脂肪酸生物合成类似的途径，但它代表了这种生物合成的一种新亚型。我们从Xellobdus budapestensis中鉴定并阐明了这类化合物的另一个成员的结构，其被命名为xenoGUFamine。在该化合物中，多胺部分连接到非核糖体形成的环肽上，环化机制未知。XenoGUFamine还显示出广泛的抗微生物活性，但也具有高度细胞毒性。初步工作显示，几种Xobacterhabdus以及与线虫共生并具有昆虫病原性的Photorhabdus菌株能够产生类似的化合物。随后对这些细菌中的几种的基因组序列的分析也导致了各自的生物合成基因簇的鉴定。Polyagmatine天然产物与nemaucin相似。这第二个不寻常的天然产物类别的唯一已知成员是腐草霉素G，nemaucin和cabanillasin。Nemauc in和cabanillasin已经从Xellobhabdus cabanillasii中分离出来，并被一家法国公司描述在专利中，因为它们也显示出与多胺类似的广泛和有效的抗微生物活性。Nemaucin具有与xenoGUFamine非常相似的肽部分，但携带聚胍丁胺而不是聚胺部分。目前还不知道这种极不寻常的polyagmatine部分的生物合成。在这个项目中，这些非常不寻常的天然产物，这显然是非常常见的昆虫病原细菌类的其他成员，将被确定，并阐明其结构。将鉴定和分析相应的生物合成基因簇，并在体外表征所选酶。此外，将更详细地研究这些化合物的生物活性，并将进行关于这些化合物作用模式的首次实验。

Entomopathogenic bacteria of the genera Photorhabdus and Xenorhabdus have been proven to be a rich source for novel natural products. However, their structure and biosynthesis is often still unknown. Therefore the biosynthesis of two structurally very unusual natural product classes will be investigated in detail in this project:1. Polyamine natural products with similarity to zeamine.Zeamine is only one of three known members of a highly unusual class of natural products with broad antimicrobial activity. It is a linear long-chain amine (>30 carbon atoms in length) with additional amine substituents. Biochemically, this unusual structure in likely to be derived from a pathways similar to the biosynthesis of polyunsaturated fatty acids but it represents a new subtype of this biosynthesis. From Xenorhabdus budapestensis we have identified and elucidated the structure of another member of this class of compounds, which was named xenoGUFamine. In this compound the polyamine moiety is attached to a nonribosomally made cyclic peptide with the cyclisation mechanism being unknown. XenoGUFamine also shows broad antimicrobial activity but is also highly cytotoxic. Preliminary work revealed that several Xenorhabdus but also Photorhabdus strains that live in symbiosis with nematodes and are entomopathogenic are able to produce similar compounds. Subsequent analysis of the genome sequences of several of these bacteria also led to the identification of the respective biosynthesis gene clusters.2. Polyagmatine natural products with similarity to nemaucin.The only known members of this second unusual class of natural products are phleomycin G, nemaucin and cabanillasin. Nemaucin and cabanillasin have been isolated from Xenorhabdus cabanillasii and were described in patents by a French company because they also show a broad and potent antimicrobial activity similar to the polyamines. Nemaucin has a peptide moiety very similar to that of xenoGUFamine but carries a polyagmatine instead of the polyamine moiety. Currently nothing in known about the biosynthesis of this highly unusual polyagmatine moiety.In this project additional members of these very unusual classes of natural products, which obviously is very common in entomopathogenic bacteria, will be identified and their structures will be elucidated. The respective biosynthesis gene clusters will be identified and analysed and selected enzymes will be characterized in vitro. Additionally, the biological activity of these compounds will be investigated in more detail and first experiments regarding the mode of action of these compounds will be performed.