Thioesterase Inhibitors of Mycolic Acid Biosynthesis as Antitubercular Agents

描述（由申请人提供）：结核分枝杆菌是结核病（TB）的病原体，是世界上导致传染病死亡的主要细菌病原体。这种生长缓慢的生物体的一个主要特点是其厚厚的蜡质细胞壁对许多药物提供了内在的屏障，这使得它难以治疗。霉菌酸是分枝杆菌细胞包膜的核心成分之一，对存活至关重要。一线药物异烟肼抑制了参与霉菌酸生物合成早期阶段的InhA酶；然而，对这种药物的耐药性促使人们对霉菌酸合成中涉及的其他潜在酶靶点进行研究。最近，一种被称为pks 13的单体聚酮合成酶被确定，它执行最终的生物合成操作，导致霉菌酸。聚酮合成酶是一种多功能酶，在过去的十年中，由于其参与生物活性天然产物的合成而得到了广泛的研究，这一领域被称为组合生物合成。研究发现pks参与了霉菌酸的合成，揭示了这些令人着迷的酶的一个更险恶的作用。合理设计靶向Pks13关键结构域之一的小分子抑制剂将被合成。这些将使用无细胞酶测定法测定体外活性。将采用基于结构和基于配体的计算方法来深入了解观察到的活性数据。将进一步评估活性化合物对全细胞结核分枝杆菌的作用。将进行脂质分析和微阵列分析的结合，以验证所提出的作用机制。这项拟议的研究有望验证Pks13作为药物靶点，并可能导致一类新的抗结核化合物靶向霉菌酸生物合成的倒数第二步。此外，这种策略可能适用于抑制来自其他病原微生物的关键PKSs。

DESCRIPTION (provided by applicant): Mycobacterium tuberculosis the causative agent of Tuberculosis (TB) is the leading cause of infectious disease mortality in the world by a bacterial pathogen. A primary feature of this slow-growing organism that makes it difficult to treat is the thick waxy cell wall that provides an intrinsic barrier to many drugs. The mycolic acids represent one of the central components of the mycobacterial cell envelope and are essential for survival. The first-line drug isoniazid inhibits the enzyme known as InhA involved in early stages of mycolic acid biosynthesis; however, resistance to this agent has prompted research into other potential enzyme targets involved in mycolic acid synthesis. Recently, a monomodular polyketide synthase known as pks 13 was identified that performs the final biosynthetic operation leading to mycolic acids. Polyketide synthases are multifunctional enzymes and have been intensively investigated in the last decade for their involvement in the synthesis of bioactive natural products, a field termed combinatorial biosynthesis. The findings that PKSs are involved in the synthesis of the mycolic acids uncover a more sinister role for these fascinating enzymes. Rationally designed small-molecule inhibitors targeting one of the crucial domains of Pks13 will be synthesized. These will be assayed for in vitro activity using a cell-free enzyme assay. Structure-based and ligand-based computational methods will be employed to provide insight into the observed activity data. Active compounds will be further evaluated against whole-cell M. tuberculosis. A combination of lipid analysis and microarray profiling will be performed to verify the proposed mechanism of action. This proposed research is expected to validate Pks13 as a drug target and may lead to a new class of antitubercular compounds that target the penultimate step of mycolic acid biosynthesis. Additionally, this strategy may be adapted to inhibit critical PKSs from other pathogenic microorganisms.