Quinolinate salvage and insights for targeting NAD biosynthesis in group A streptococci.
Quinolinate salvage and insights for targeting NAD biosynthesis in group A streptococci.
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喹啉盐抢救和针对 A 组链球菌 NAD 生物合成的见解。
DOI：
10.1128/jb.02002-12
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发表时间：
2013
影响因子：
3.2
通讯作者：
Osterman,AndreiL
中科院分区：
文献类型：
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作者：
Sorci,Leonardo;Blaby,IanK;Rodionova,IrinaA;DeIngeniis,Jessica;Tkachenko,Sergey;deCrecy-Lagard,Valerie;Osterman,AndreiL
必需辅酶NAD在所有生物体的代谢反应和细胞调节中发挥着重要作用。因此，NAD 合成已被研究作为新型抗菌靶点的来源。基于跨物种基因组学重建 A 组链球菌 (GAS) 中的 NAD 代谢，结合化脓性链球菌的重点实验测试，可以更好地了解病原体中的 NAD 代谢。预测的烟酸营养缺陷症以及烟酰胺酶 PncA 在烟酰胺 (Nm) 利用中的重要作用得到了实验验证。在烟酸盐 (Na) 存在的情况下，PncA 是可有可无的，因此排除了它作为可行抗菌靶点的可能性。尽管不存在 NADde 新合成的其他基因，但“孤儿”NadC 酶的功能已被阐明，该酶在所有 GAS 物种中都独特存在。事实上，当 Qa 作为唯一的吡啶前体存在时，来自化脓性链球菌的 NadC 的喹啉 (Qa) 磷酸核糖基转移酶活性使生物体能够维持生长。最后，GAS 物种中功能性上游补救途径的冗余将潜在药物靶点的选择范围缩小到 NAD 合成中两个不可或缺的下游酶：烟酸腺苷酸转移酶（NadD 家族）和 NAD 合成酶（NadE 家族）。 NadD 的生化特征证实了其在化脓性链球菌中的功能作用，并且其作为抗菌靶点的潜力得到了先前鉴定的 NadD 酶家族 I 类抑制剂的抑制研究的支持。其中一种抑制剂在体外可有效抑制化脓性链球菌 NadD (sp.NadD)（50% 抑制浓度 [IC50]，15 μM），与 aKiof 8 μM 表现出非竞争性机制。
The essential coenzyme NAD plays important roles in metabolic reactions and cell regulation in all organisms. As such, NAD synthesis has been investigated as a source for novel antibacterial targets. Cross-species genomics-based reconstructions of NAD metabolism in group A streptococci (GAS), combined with focused experimental testing in Streptococcus pyogenes, led to a better understanding of NAD metabolism in the pathogen. The predicted niacin auxotrophy was experimentally verified, as well as the essential role of the nicotinamidase PncA in the utilization of nicotinamide (Nm). PncA is dispensable in the presence of nicotinate (Na), ruling it out as a viable antibacterial target. The function of the “orphan” NadC enzyme, which is uniquely present in all GAS species despite the absence of other genes of NADde novosynthesis, was elucidated. Indeed, the quinolinate (Qa) phosphoribosyltransferase activity of NadC from S. pyogenes allows the organism to sustain growth when Qa is present as a sole pyridine precursor. Finally, the redundancy of functional upstream salvage pathways in GAS species narrows the choice of potential drug targets to the two indispensable downstream enzymes of NAD synthesis, nicotinate adenylyltransferase (NadD family) and NAD synthetase (NadE family). Biochemical characterization of NadD confirmed its functional role in S. pyogenes, and its potential as an antibacterial target was supported by inhibition studies with previously identified class I inhibitors of the NadD enzyme family. One of these inhibitors efficiently inhibited S. pyogenes NadD (sp.NadD)in vitro(50% inhibitory concentration [IC50], 15 μM), exhibiting a noncompetitive mechanism with aKiof 8 μM.