Department of Chemical Biology and Therapeutics, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, Tennessee 38105, United States.
Department of Microbiology, Immunology, and Biochemistry, The University of Tennessee Health Science Center, 858 Madison Avenue, Memphis, Tennessee 38163, United States.
ACS Infect Dis. 2020 Mar 13;6(3):467-478. doi: 10.1021/acsinfecdis.9b00406. Epub 2020 Jan 13.
Increasing rates of drug-resistant Gram-negative (GN) infections, combined with a lack of new GN-effective antibiotic classes, are driving the need for the discovery of new agents. Bacterial metabolism represents an underutilized mechanism of action in current antimicrobial therapies. Therefore, we sought to identify novel antimetabolites that disrupt key metabolic pathways and explore the specific impacts of these agents on bacterial metabolism. This study describes the successful application of this approach to discover a new series of chemical probes, -(phenyl)thioacetamide-linked 1,2,3-triazoles (TAT), that target cysteine synthase A (CysK), an enzyme unique to bacteria that is positioned at a key juncture between several fundamental pathways. The TAT class was identified using a high-throughput screen against designed to identify modulators of pathways related to folate biosynthesis. TAT analog synthesis demonstrated a clear structure-activity relationship, and activity was confirmed against GN antifolate-resistant clinical isolates. Spontaneous TAT resistance mutations were tracked to CysK, and mode of action studies led to the identification of a false product formation mechanism between the CysK substrate -acetyl-l-serine and the TATs. Global transcriptional responses to TAT treatment revealed that these antimetabolites impose substantial disruption of key metabolic networks beyond cysteine biosynthesis. This study highlights the potential of antimetabolite drug discovery as a promising approach to the discovery of novel GN antibiotics and the pharmacological promise of TAT CysK probes.
耐药革兰氏阴性（GN）感染率不断上升，加上缺乏新的有效治疗 GN 的抗生素类别，这促使人们需要开发新的药物。细菌代谢是目前抗菌治疗中未充分利用的作用机制。因此，我们试图寻找新的抗代谢物，这些抗代谢物可以破坏关键的代谢途径，并探索这些药物对细菌代谢的具体影响。本研究描述了成功应用这种方法来发现一系列新的化学探针，即-(苯基)硫代乙酰胺连接的 1,2,3-三唑（TAT），这些探针靶向半胱氨酸合酶 A（CysK），CysK 是一种独特存在于细菌中的酶，位于几个基本途径的关键交汇点。TAT 类化合物是通过针对设计的高通量筛选发现的，旨在鉴定与叶酸生物合成相关途径的调节剂。TAT 类似物的合成显示出明显的结构-活性关系，并且对 GN 抗叶酸耐药的临床分离株具有活性。自发的 TAT 耐药突变被追踪到 CysK，作用机制研究导致鉴定出 CysK 底物 -乙酰-l-丝氨酸与 TAT 之间形成假产物的机制。TAT 处理的全转录组响应表明，这些抗代谢物除了破坏半胱氨酸生物合成外，还会对关键代谢网络造成严重破坏。本研究强调了抗代谢物药物发现作为发现新型 GN 抗生素的有前途的方法的潜力，以及 TAT CysK 探针的药理学潜力。
