Rational, structure-based inhibitor design, synthesis and evaluation as a first step towards the discovery of new anti-tuberculosis drugs

背景：结核分枝杆菌和牛分枝杆菌分别是人类和动物结核病的主要病原。世界卫生组织(WHO)报告称，2018年有150万人(包括251K艾滋病毒携带者)死于结核病，1000万人患病，是所有传染病中最高的。已经观察到越来越多的人对用于治疗结核病的药物产生耐药性，包括表现出极端耐药性的菌株(XDR-TB)。Defra报告称，在截至2018年9月的12个月里，英国有2805头牛被检测出牛结核病呈阳性，在过去十年里，英国不得不屠宰30.5万头牛，代价是5亿GB。因此，治疗或根除结核病的方法对人类和动物的健康都至关重要。与其他革兰氏阳性细菌相比，分枝杆菌有一种不寻常的、更复杂的细胞壁结构。细菌的外表面是由真菌酸(~C60长链脂肪酸)的疏水蜡状涂层形成的(Alderwick等人。冷泉港透视医疗。2015、5、A021113)，其充当伪外膜。它位于一种多糖结构上，阿拉伯半乳糖含有几种稀有糖(半乳呋喃糖/阿拉伯呋喃糖/鼠李糖)，然后连接到肽聚糖层。这种“隐形”的外套使细菌免受宿主的防御，使它们能够在不引发宿主反应的情况下，在哺乳动物组织中定居并形成生物膜。我们可以有选择地用抑制剂/药物靶向分枝杆菌特有的几种酶，减少脱靶毒性的机会。研究项目：这将涉及新化合物的设计、合成和评估，作为选定的目标酶的假定抑制剂：参与真菌酸生物合成的inha(一种烯醇还原酶)；参与半乳聚糖生物合成的UGM和GlfT2。这些酶具有高分辨率的X射线结构，使得新的抑制剂设计可以在合成之前使用包括GOLD或OEDocking在内的蛋白质-配体对接程序在电子计算机中进行测试。对于Inha来说，导致耐药性的临床重要突变是已知的，新的化合物可以与这些突变体对接，以测试它们的结合是否会受到影响。大多数结核病病例在第三世界，因此新药需要易于生产和具有口服活性，以将成本降至最低。研究将集中在上述一种/两种酶上。学生将从小组提供的载体中表达酶(S)，并根据需要合成其分析底物。初始测试化合物将通过对接现有的小分子/片段文库(大小)来设计

Background: Mycobacterium tuberculosis and M. bovis are the main causes of tuberculosis (TB) in humans and animals respectively. The World Health Organisation (WHO) reported that 1.5M people (including 251K with HIV) died from TB and 10M fell ill in 2018, the highest of any infectious disease. Increasing occurrences of drug resistance to the drugs used to treat TB include strains showing extreme drug resistance (XDR-TB) have been observed. DEFRA reported that 2,805 herds of cattle in Great Britain tested positive for bovine TB in the 12 months to Sept 2018, with 305K cattle having to be slaughtered in GB over the last decade at the cost of £500M. Methods of treating or eradicating TB are therefore crucial to both human and animal health. Mycobacteria have an unusual and more complex cell wall structure than other Gram-positive bacteria. The exterior surface of the bacterium is formed from a hydrophobic, waxy coat of mycolic acids (~C60 long chain fatty acids) (Alderwick et al. Cold Spring Harb Perspect Med. 2015, 5, a021113) that acts as a pseudo-outer membrane. This sits on a polysaccharide structure, arabinogalactan that contains several rare sugars (galactofuranose/arabinofuranose/rhamnose) which is then attached to the peptidoglycan layer. This 'stealth' coat masks the bacteria from its host's defences and allows them to colonize mammalian tissues and form biofilms without triggering a host response. We can selectively target several enzymes unique to Mycobacteria with inhibitors/drugs with a reduced chance of off-target toxicity. Research Project: This will involve the design, synthesis and evaluation of new compounds as putative inhibitors of selected target enzymes: InhA (an enoyl reductase) involved in mycolic acidbiosynthesis; UGM and GlfT2 involved in galactan biosynthesis. There are high resolution X-ray structures available for these enzymes allowing new inhibitor designs to be tested in silico using protein-ligand docking programs including GOLD or OEDocking prior to their synthesis. For InhA, the clinically important mutations that cause resistance are known and new compounds can be docked against these mutants to test if their binding will be impacted. The majority of TB cases are in the third world, therefore new drugs need to be easy to produce and be orally active to minimise their cost.The research will focus on one/two of the enzymes mentioned above. The student will express the enzyme(s) from vectors available in the group and synthesize their assay substrates as necessary. Initial test compounds will be designed by docking existing small molecule/fragment libraries (size