Medical Proteomics Research Center, Korea Research Institute of Bioscience and Biotechnology, Daejeon, South Korea.
Biochem Biophys Res Commun. 2012 Jul 13;423(4):638-41. doi: 10.1016/j.bbrc.2012.05.156. Epub 2012 Jun 8.
Nitroreductases comprise a group of FMN- or FAD-dependent enzymes that reduce nitrosubstituted compounds by using NAD(P)H, and are found in bacterial species and yeast. Although there is little information on the biological functions of nitroreductases, some studies suggest their possible involvement in oxidative stress responses. In the yeast Saccharomyces cerevisiae, a putative nitroreductase protein, Frm2, has been identified based on its sequence similarity with known bacterial nitroreductases. Frm2 has been reported to function in the lipid signaling pathway. To study the functions of Frm2, we measured the nitroreductase activity of purified Frm2 on 4-nitroquinoline-N-oxide (4-NQO) using NADH. LC-MS analysis of the reaction products revealed that Frm2 reduced NQO into 4-aminoquinoline-N-oxide (4-AQO) via 4-hydroxyaminoquinoline (4-HAQO). An Frm2 deletion mutant exhibited growth inhibition in the presence of 4-NQO. Thus, in this study, we demonstrate a novel nitroreductase activity of Frm2 and its involvement in the oxidative stress defense system.
硝基还原酶包含一组 FMN 或 FAD 依赖性酶，它们通过使用 NAD(P)H 将亚硝代化合物还原，存在于细菌物种和酵母中。尽管关于硝基还原酶的生物学功能的信息很少，但一些研究表明它们可能参与氧化应激反应。在酵母酿酒酵母中，根据其与已知细菌硝基还原酶的序列相似性，已经鉴定出一种假定的硝基还原酶蛋白 Frm2。Frm2 已被报道在脂质信号通路中发挥作用。为了研究 Frm2 的功能，我们使用 NADH 测量了纯化的 Frm2 在 4-硝基喹啉-N-氧化物（4-NQO）上的硝基还原酶活性。反应产物的 LC-MS 分析表明，Frm2 通过 4-羟基氨基喹啉（4-HAQO）将 NQO 还原为 4-氨基喹啉-N-氧化物（4-AQO）。Frm2 缺失突变体在存在 4-NQO 时表现出生长抑制。因此，在这项研究中，我们证明了 Frm2 的一种新的硝基还原酶活性及其参与氧化应激防御系统。
