The biosynthesis and enzymology of complex rubromycin and tropone marine bacterial natural products

长期以来，海洋天然产品在很大程度上仍然是一种尚未开发和探索不足的药学化合物来源。与此同时，许多具有生物活性的海洋天然产物已被表征，其中许多来自细菌。通常，这些分子具有高度复杂的结构，阻碍或完全阻碍化学合成，而它们的生物合成取决于不寻常的酶反应。我的研究项目侧重于详细表征酶学基础的生态和药学上有趣的天然产物的生物合成，例如，作为海洋无脊椎动物（珊瑚，被囊动物，牡蛎或海绵）的防御工具，例如基于肌钙蛋白的天然产品，如tropodiethic acid或rosebacticides。这些化合物是通过例如，受玫瑰杆菌属或珊瑚相关假弧菌属等主要海洋细菌的影响，在那里它们作为有效的珊瑚保护剂、除藻剂或细菌信号分子。在过去，我们阐明了细菌苯乙酸分解代谢途径，并确定了假定的前体的托品天然产物。我们现在的目标是获得这些代谢物的生物合成所需的所有酶，并详细描述它们，以使这些天然产物的体外酶促合成成为可能，并深入了解潜在的生物化学。作为该项目的第二个支柱，将研究由放线菌产生的红霉素家族芳香聚酮化合物的生物合成，放线菌通常从海洋被囊动物中分离出来。直到最近，关于红霉素的生物合成的细节知之甚少，特别是在芳香族聚酮化合物中例外的螺酮缩酮药效团，其有效的生物活性是必不可少的。我们在体外成功地重建了完整的酶促螺缩酮pharamacophore形成，从而深入了解新的酶反应，并发现了各种以前未被识别的中间体。我们现在试图解决这些酶的结构，并进行详细的机理研究，以进一步了解这些复杂的生物合成步骤。此外，将研究修饰螺缩酮的最终途径步骤。两个项目的目的都是阐明与生态和药学相关的海洋天然产品生物合成的酶学基础。这种知识可能是有用的，例如，用于建立体内和体外生产平台和生物活性化合物的生物工程，同时也促进了我们对自然界中结构复杂性如何产生的基本理解。

Marine natural products remained a largely untapped and underexplored source of pharmaceutically interesting compounds for a long time. Meanwhile, numerous bioactive marine natural products have been characterized, many of which derive from bacteria. Often, these molecules feature highly intricate structures that impede or completely thwart chemical synthesis, while their biosynthesis depends on unusual enzyme reactions. My research project focusses on the detailed characterization of the enzymology underlying the biosynthesis of ecologically and pharmaceutically interesting natural products that, e.g., serve as defensive tools for marine invertebrates (corals, tunicates, oysters, or sponges), as exemplified by tropone-based natural products such as tropodithietic acid or rosebacticides. These compounds are produced, e.g., by predominant marine bacteria such as Roseobacter or coral-associated Pseudovibrio sp., where they serve as potent coral protectants, algaecides, or bacterial signaling molecules. In the past, we elucidated the bacterial phenylacetic acid catabolic pathway and identified the postulated precursor for tropone natural products. We now aim to acquire all enzymes required for the biosynthesis of thee metabolites and characterize them in detail to enable the in vitro enzymatic synthesis of these natural products and gain insight into the underlying biochemistry. As a second pillar of the project, the biosynthesis of the rubromycin family of aromatic polyketides will be investigated that are produced by Actinobacteria, which are commonly isolated from marine tunicates. Until recently, little details were known about the biosynthesis of rubromycins, in particular of the spiroketal pharmacophore that is exceptional among aromatic polyketides and essential for their potent bioactivities. We successfully reconstituted the complete enzymatic spiroketal pharamacophore formation in vitro that granted insight into novel enzyme reactions and led to the discovery of various previously unrecognized intermediates. We now seek to solve the structures of these enzymes and conduct detailed mechanistic studies to further our understanding of these complex biosynthetic steps. Moreover, final pathway steps that modify the spiroketal will be investigated. Taken together, both project parts aim at elucidating the enzymology underlying the biosyntheses of ecologically and pharmaceutically relevant marine natural products. This knowledge may be useful, e.g., for the establishment of in vivo and in vitro production platforms and bioengineering of bioactive compounds, while also furthering our fundamental understanding of how structural complexity is generated in nature.