Polymyxin B Identified as an Inhibitor of Alternative NADH Dehydrogenase and Malate: Quinone Oxidoreductase from the Gram-positive Bacterium Mycobacterium smegmatis
Polymyxin B Identified as an Inhibitor of Alternative NADH Dehydrogenase and Malate: Quinone Oxidoreductase from the Gram-positive Bacterium Mycobacterium smegmatis
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DOI：
10.1093/jb/mvp096
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发表时间：
2009-10-01
影响因子：
2.7
通讯作者：
Kita, Kiyoshi
中科院分区：
文献类型：
--
作者：
Mogi, Tatsushi;Murase, Yoshiro;Kita, Kiyoshi
结核病是世界上单一感染源导致死亡的主要原因，多药耐药菌株的出现促使我们开发具有新靶点和机制的新药。在这里，我们用耻垢分枝杆菌膜结合酶筛选天然抗生素库，并鉴定了多粘菌素B（阳离子十肽）和纳米霉素A（萘醌衍生物）作为替代性NADH脱氢酶的抑制剂[50%抑制浓度（IC 50）值分别为1.6和31 μ g/ml]和苹果酸：醌氧化还原酶（IC 50值分别为4.2和49 μ g/ml）。动力学分析表明，多粘菌素B的抑制作用的主要位点是醌结合位点。由于泛醌-1和抑制剂敏感性的Km值的相似性，我们研究了放线菌酶的氨基酸序列，并发现了L-苹果酸和醌类的可能结合位点。多粘菌素B和纳米霉素A的杀菌活性的机制分别是破坏细菌膜和产生活性氧，而本研究揭示了它们对细菌膜结合的脱氢酶的抑制活性。用细菌呼吸酶筛选文库导致了前所未有的发现，因此我们希望继续努力可以确定针对分枝杆菌呼吸酶的新药的先导化合物。
Tuberculosis is the leading cause of death due to a single infectious agent in the world and the emergence of multidrug-resistant strains prompted us to develop new drugs with novel targets and mechanism. Here, we screened a natural antibiotics library with Mycobacterium smegmatis membrane-bound dehydrogenases and identified polymyxin B (cationic decapeptide) and nanaomycin A (naphtoquinone derivative) as inhibitors of alternative NADH dehydrogenase [50% inhibitory concentration (IC50) values of 1.6 and 31 mu g/ml, respectively] and malate: quinone oxidoreductase (IC50 values of 4.2 and 49 mu g/ml, respectively). Kinetic analysis on inhibition by polymyxin B showed that the primary site of action was the quinone-binding site. Because of the similarity in K-m value for ubiquinone-1 and inhibitor sensitivity, we examined amino acid sequences of actinobacterial enzymes and found possible binding sites for L-malate and quinones. Proposed mechanisms of polymyxin B and nanaomycin A for the bacteriocidal activity were the destruction of bacterial membranes and production of reactive oxygen species, respectively, while this study revealed their inhibitory activity on bacterial membrane-bound dehydrogenases. Screening of the library with bacterial respiratory enzymes resulted in unprecedented findings, so we are hoping that continuing efforts could identify lead compounds for new drugs targeting to mycobacterial respiratory enzymes.