Structure and biosynthesis of unusual polyamine and polyagmatine natural products

光杆菌属和致病杆菌属的昆虫病原细菌已被证明是新天然产物的丰富来源。然而，它们的结构和生物合成往往仍然未知。因此，本项目将详细研究两类结构非常特殊的天然产物的生物合成：1.与玉米胺相似的多胺天然产物。玉米醇胺只是具有广泛抗菌活性的极不寻常的天然产物的三个已知成员之一。它是一种直线型长链胺(&gt；30个碳原子长度)，带有附加的胺取代基。在生物化学上，这种不寻常的结构很可能来自一种类似于多不饱和脂肪酸生物合成的途径，但它代表了这种生物合成的一个新亚型。我们从布达佩斯杆菌中鉴定并鉴定了这类化合物中的另一个成员的结构，命名为异谷饥胺。在该化合物中，多胺部分连接到非核糖体制造的环肽上，环化机制未知。XenoGU Famine也显示出广泛的抗菌活性，但也具有高度的细胞毒性。初步工作表明，与线虫共生的几个Xnowhabdus菌株以及Photorhabdus菌株都能够产生类似的化合物。随后对其中几个细菌的基因组序列的分析也导致了对各自生物合成基因簇的识别。与根瘤菌素相似的聚乙二醇胺天然产物。这第二类不寻常的天然产物中唯一已知的成员是金霉素G、根瘤菌素和卡巴拉菌素。Nemucin和Cabanillasin已经从Xnowhabdus Cabanillasii中分离出来，并被一家法国公司在专利中描述，因为它们也显示出与多胺类似的广泛和有效的抗菌活性。Nemuchin的多肽部分与异谷饥胺非常相似，但携带的是聚苷丁胺而不是多胺部分。目前还不知道这种非常不寻常的聚苷甲胺的生物合成。在这个项目中，将鉴定这些非常不寻常的天然产物的额外成员，这显然在昆虫病原细菌中非常常见，并将阐明它们的结构。将对各自的生物合成基因簇进行鉴定和分析，并将在体外对选定的酶进行特性鉴定。此外，还将更详细地研究这些化合物的生物活性，并进行有关这些化合物作用模式的初步实验。

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.