EthA, a common activator of thiocarbamide-containing drugs acting on different mycobacterial targets
EthA, a common activator of thiocarbamide-containing drugs acting on different mycobacterial targets
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DOI：
10.1128/aac.01063-06
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发表时间：
2007-03-01
影响因子：
4.9
通讯作者：
Kremer, Laurent
中科院分区：
文献类型：
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作者：
Dover, Lynn G.;Alahari, Anuradha;Kremer, Laurent
目前的许多抗分枝杆菌药物需要某种形式的细胞活化来暴露反应基团，这些反应基团反过来将与它们的特异性靶标结合。因此，了解当前抗分枝杆菌药物的激活机制不仅有助于破译耐药性机制，而且还可能促进替代激活策略或不需要此类过程的类似物的开发。在本文中，通过使用牛分枝杆菌BCG的遗传定义的菌株，我们提供了证据表明，EthA，以前显示激活乙硫异烟胺，也将isoxyl（ISO）和thiacetazone（TAC）转化为活性物质。这些结果得到了使用纯化重组EthA开发的体外试验的进一步支持，该试验允许直接评估ISO的代谢。有趣的是，[C-14]乙酸标记的培养物的生化分析表明，所有这些EthA激活的药物通过与特定靶点结合的不同机制抑制分枝菌酸生物合成。该报告也是首次描述TAC的分子作用机制，TAC是一种缩氨基硫脲抗菌药物，在许多发展中国家仍作为二线药物用于治疗结核病。总之，结果表明EthA是含硫脲类药物的常见活化剂。EthA的广泛特异性现在可用于改善这些药物的活化过程，这可能有助于克服与临床使用硫脲相关的毒性问题。
Many of the current antimycobacterial agents require some form of cellular activation unmasking reactive groups, which in turn will bind to their specific targets. Therefore, understanding the mechanisms of activation of current antimycobacterials not only helps to decipher mechanisms of drug resistance but may also facilitate the development of alternative activation strategies or of analogues that do not require such processes. Herein, through the use of genetically defined strains of Mycobacterium bovis BCG we provide evidence that EthA, previously shown to activate ethionamide, also converts isoxyl (ISO) and thiacetazone (TAC) into reactive species. These results were further supported by the development of an in vitro assay using purified recombinant EthA, which allowed direct assessment of the metabolism of ISO. Interestingly, biochemical analysis of [C-14] acetate-labeled cultures suggested that all of these EthA-activated drugs inhibit mycolic acid biosynthesis via different mechanisms through binding to specific targets. This report is also the first description of the molecular mechanism of action of TAC, a thiosemicarbazone antimicrobial agent that is still used in the treatment of tuberculosis as a second-line drug in many developing countries. Altogether, the results suggest that EthA is a common activator of thiocarbamide-containing drugs. The broad specificity of EthA can now be used to improve the activation process of these drugs, which may help overcome the toxicity problems associated with clinical thiocarbamide use.