Elucidation and inhibition of the biosynthetic pathway to the anthrax stealth siderophore petrobactin

炭疽杆菌是引起炭疽病的细菌，炭疽病是一种经常致命的动物和人类疾病。近年来，由于其孢子有可能被用作生物恐怖剂，因此引起了相当大的关注。虽然炭疽可以使用目前可用的抗生素（如环丙沙星）治疗，但炭疽杆菌可以通过基因工程使其对所有目前可用的抗生素具有抗性。这种基因工程菌株造成的生物恐怖主义威胁是相当大的，因此需要开发对B有活性的新抗生素。炭疽病铁是几乎所有细菌（包括B）增殖的必需元素。炭疽病因此，感染性细菌从其宿主获得铁的系统代表了开发治疗剂的潜在目标。铁载体是大多数细菌分泌的代谢产物，与三价铁紧密结合。在哺乳动物细胞内和哺乳动物细胞之间，三价铁与蛋白质（例如转铁蛋白和乳铁蛋白）紧密结合。由感染性细菌产生的铁载体能够从这些蛋白质中去除三价铁并将其运输到细菌细胞中。对于几种感染性细菌，已知抑制它们用于铁载体合成的途径会强烈减弱或消除它们引起感染的能力。B。炭疽菌已显示分泌两种铁载体，称为杆菌素和岩杆菌素。而B不需要杆菌素。在小鼠炭疽菌感染模型的生长中，petrobactin起着显著的作用。这归因于petrobactin而不是bacillibactin避开哺乳动物免疫系统的能力，表明设计用于抑制催化petrobactin组装的酶的小分子可能是针对B的有效抗生素。炭疽病为了设计这样的抑制剂，需要在分子水平上对这些酶如何催化petrobactin的组装有基本的理解。遗传学研究表明，petrobactin生物合成途径是一个独特的杂交两个众所周知的铁载体生物合成途径，其中之一是几乎完全未在分子水平上探索。生物化学研究已经开始揭示petrobactin生物合成的分子细节，并导致发现了新的和有趣的酶，其在生产用于合成候选药物和其他精细化学品的有价值的构件中具有潜在的应用。本论文旨在详细研究petrobactin合成中一个关键酶的催化特性，并设计、合成和测试该酶家族的第一个抑制剂。它还旨在研究参与petrobactin组装的另外两种重要酶的催化特性。这将阐明B使用的途径。炭疽菌用于petrobactin合成，目前尚不清楚。

Bacillus anthracis is the bacterium that causes anthrax, a frequently fatal disease of animals and humans. It has attracted considerable attention in recent years because of the potential to use its spores as a biological terror agent. While anthrax can be treated using currently available antibiotics e.g. ciprofloxacin, Bacillus anthracis could be genetically engineered to make it resistant to all currently available antibiotics. The bioterrorism threat posed by such genetically engineered strains would be considerable and there is thus a need to develop new antibiotics that are active against B. anthracis. Iron is an essential element for the proliferation of virtually all bacteria including B. anthracis. As a consequence, the systems used by infectious bacteria to acquire iron from their hosts represent potential targets for the development of therapeutic agents. Siderophores are metabolites excreted by most bacteria that bind tightly to ferric iron. Within and between mammalian cells ferric iron is tightly bound by proteins (e.g. transferrin and lactoferrin). Siderophores produced by infectious bacteria are able to remove the ferric iron from these proteins and transport it into the bacterial cell. For several infectious bacteria, inhibition of the pathways they use for siderophore synthesis is known to strongly attenuate or abrogate their ability to cause infection. B. anthracis has been shown to excrete two siderophores called bacillibactin and petrobactin. While bacillibactin is not required for B. anthracis growth in mouse models of infection, petrobactin plays a significant role. This has been attributed to the ability of petrobactin, but not bacillibactin, to avoid the mammalian immune system, suggesting that small molecules designed to inhibit the enzymes catalysing assembly of petrobactin may be effective antibiotics against B. anthracis. To design such inhibitors a fundamental understanding at the molecular level of how these enzymes catalyse the assembly of petrobactin is required. Genetic studies have shown that the petrobactin biosynthetic pathway is a unique hybrid of two well-known pathways for siderophore biosynthesis, one of which is almost completely unexplored at the molecular level. Biochemical studies have begun to reveal the molecular details of petrobactin biosynthesis and have led to the discovery of novel and interesting enzymes with potential applications in the production of valuable building blocks for the synthesis of drug candidates and other fine chemicals. This proposal aims to investigate the catalytic properties of a key enzyme in petrobactin synthesis in detail, as well as design, synthesise and test the first inhibitors of this enzyme family. It also aims to investigate the catalytic properties of two other important enzymes involved in petrobactin assembly. This will clarify the pathway used by B. anthracis for petrobactin synthesis, which at present is unclear.