The thienopyrimidine TP053 is an antitubercular prodrug active against both replicating and nonreplicating Mycobacterium tuberculosis (M. tuberculosis) cells, which requires activation by the mycothiol-dependent nitroreductase Mrx2. The investigation of the mechanism of action of TP053 revealed that Mrx2 releases nitric oxide from this drug both in the enzyme assays with purified Mrx2 and in mycobacterial cultures, which can explain its activity against nonreplicating bacilli, similar to pretomanid activated by the nitroreductase Ddn. In addition, we identified a highly reactive metabolite, 2-(4-mercapto-6-(methylamino)-2-phenylpyrimidin-5-yl)ethan-1-ol, which can contribute to the antimycobacterial effects on replicating cells as well as on nonreplicating cells. In summary, we explain the mechanism of action of TP053 on both replicating and nonreplicating M. tuberculosis and report a novel activity for Mrx2, which in addition to Ddn, represents another example of nitroreductase releasing nitric oxide from its substrate. These findings are particularly relevant in the context of drugs targeting nonreplicating M. tuberculosis, which is shown to be killed by increased levels of nitric oxide.

中文翻译：

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硫代嘧啶抗结核前药TP053作用机理的新见解。

硫代嘧啶TP053是一种抗结核前药，对复制型和非复制型结核分枝杆菌（M. tuberculosis）细胞均具有活性，需要通过分枝硫醇依赖性硝基还原酶Mrx2进行激活。TP053作用机理的研究表明，在用纯化的Mrx2进行酶测定和在分枝杆菌培养物中，Mrx2均从该药中释放出一氧化氮，这可以解释其对非复制型细菌的活性，类似于由硝基还原酶Ddn激活的类前manid。此外，我们发现了一种高反应活性的代谢物2-（4-巯基-6-（甲基氨基）-2-苯基嘧啶-5-基）乙-1-醇，它可以对复制细胞以及其他细菌产生抗分枝杆菌作用。在非复制细胞上。总之，我们解释了TP053对复制型和非复制型结核分枝杆菌的作用机理，并报告了Mrx2的新活性，除Ddn外，它还代表了另一种从其底物释放一氧化氮的硝基还原酶实例。这些发现在针对非复制型结核分枝杆菌的药物中尤为重要，该药物被一氧化氮水平升高所杀死。