Biosynthesis and medicinal chemistry of the capuramycin antimycobacterial antibiotics

结核病(TB)--主要由细菌病原体结核分枝杆菌(Mtb)引起-- 这种古老的疾病仍然是世界上最致命的传染病之一。最令人担忧的问题 面向未来的是耐药结核病的快速增长。世界卫生组织估计有48万人 2014年，对一线抗结核药物异烟肼和利福平耐药的结核病病例有19万人死亡。 此外，包括美国在内的多个国家已经记录了完全耐药的结核分枝杆菌。 各州。卡普拉霉素家族糖基化核苷类抗生素是抗结核药物的极佳候选药物 发现和发展，因为它们(I)被认为是具有几个不寻常结构的新的化学实体 与包括临床抗结核药物在内的所有抗生素相比的特点：(Ii)针对一种新的和必要的酶 (转位酶1；TL1)在细胞壁生物合成中，(Ii)在体外和体内具有优异的抗结核分枝杆菌活性，(Iv)是 在体外杀菌和杀死结核分枝杆菌的速度比任何一线抗结核药物都要快，并且(V)没有毒性。我们的初选 这项提案的目标是定义一种生物合成机制，用于组装不寻常的不饱和脂肪酸 卡普拉霉素中的己糖醛酸成分(目标1)和建立互补化学物质(通过 新糖随机化；目标2)和生物合成(通过天然和非天然糖基转移酶；目标3)平台 为了快速产生可筛选TL1抑制的新型己糖醛酸取代的卡普拉霉素， 抗结核分枝杆菌活性，改善药理特性。此外，这些新的卡普拉霉素类似物 将被筛选为磷酸转移酶CAPP的潜在底物或抑制剂，该酶可共价修饰 卡普拉霉素作为产生菌内的一种自我抗性策略，具有广泛的应用前景 抗性机制。预计在完成目标后，糖的新的生物合成机制 将对合并和修改进行定义。此外，这些目标的完成将提供第一个 快速询问/调整卡普拉霉素核心基本特征的实用、全面的策略 药效团，这不仅对卡普拉霉素的临床开发具有重要意义，而且可以应用于 到其他糖基化核苷抗生素，其中数十种现在已知具有不同的生物活性。

Tuberculosis (TB)—which is primarily caused by the bacterial pathogen Mycobacterium tuberculosis (Mtb)—is an ancient disease that remains one of the deadliest communicable diseases worldwide. A paramount concern heading into the future is the rapid rise in drug-resistant TB. The World Health Organization estimated 480,000 cases of TB with 190,000 deaths in 2014 with resistance to the first-line anti-TB drugs isoniazid and rifampicin. Furthermore, totally drug-resistant Mtb has now been documented in multiple countries including the United States. The capuramycin family of glycosylated nucleoside antibiotics are excellent candidates for anti-TB drug discovery and development because they (i) are considered new chemical entities with several unusual structural features compared to all antibiotics including clinical anti-TB drugs, (ii) target a novel and essential enzyme (translocase 1; TL1) in cell wall biosynthesis, (ii) have exceptional anti-Mtb activity in vitro and in vivo, (iv) are bactericidal and kill Mtb faster than any first-line anti-TB drug in vitro, and (v) have no toxicity. Our primary objectives in this proposal are to define a biosynthetic mechanism for the assembly of the unusual unsaturated hexuronic acid component in capuramycins (Aim 1) and establish complementary chemical (via neoglycorandomization; Aim 2) and biosynthetic (via native and nonnative glycosyltransferases; Aim 3) platforms for rapidly generating novel hexuronic acid-substituted capuramycins that can be screened for TL1 inhibition, anti-Mtb activity, and improved pharmacological properties. Additionally, these novel capuramycin analogues will be screened as potential substrates or inhibitors of the phosphotransferase CapP, which covalently modifies capuramycin as a strategy of self-resistance within the producing strain and is potentially a widespread resistance mechanism. It is expected that, upon completion of the aims, a new biosynthetic mechanism for sugar incorporation and modification will be defined. Furthermore, the completion of the aims will provide the first practical, comprehensive strategy to rapidly interrogate/modulate the fundamental features of capuramycin core pharmacophore, which will not only be important for the clinical development of capuramycin but can be applied to other glycosylated nucleoside antibiotics, of which dozens are now known with diverse biological activities.