Department of Biotechnology and Bioinformatics, Korea University, 2511 Sejong-ro, Sejong-si, Korea.
Department of Korean Medicine, Semyung University, 65 Semyeong-ro, Jecheon-si, Chungbuk, Korea.
J Biochem. 2019 Feb 1;165(2):197-204. doi: 10.1093/jb/mvy097.
In this study, we analysed the ahpD gene from Corynebacterium glutamicum, which may function in a H2O2-mediated stress responses. Cells overexpressing C. glutamicum ahpD (P180-ahpD) showed increased sensitivity to H2O2 when exposed to the latter in concentrations of 8 mM or greater while showing reduced expression of katA, which encodes catalase. On the other hand, cells that lack ahpD (ΔahpD) displayed increased sensitivity when exposed to low levels of H2O2 while showing katA transcription that was comparable to the level in the wild-type strain. Accordingly, transcription of ahpD and katA was stimulated by low and high concentration of H2O2, respectively. Further, the NAD+/NADH ratio was severely reduced in the ΔahpD (3.03) and P180-ahpD (0.47) strains as compared with that in the wild-type (4.55) strain. Transcriptional analysis indicated that ahpD and upstream genes such as cg2675, cg2676, cg2677 and cg2678, which were annotated as ABC-type transporter, were organized into an operon. Collectively, these findings indicate that C. glutamicum possesses bi-level defence pathways against hydrogen peroxide, involving katA and ahpD. Further, ahpD, along with cg2675-cg2678 genes, may play a novel role in cellular activities against oxidative stress.
在这项研究中，我们分析了谷氨酸棒杆菌的 ahpD 基因，该基因可能在 H2O2 介导的应激反应中发挥作用。当用 8mM 或更高浓度的 H2O2 处理时，过表达 C. glutamicum ahpD（P180-ahpD）的细胞表现出对 H2O2 的敏感性增加，而编码过氧化氢酶的 katA 的表达减少。另一方面，缺乏 ahpD（ΔahpD）的细胞在暴露于低水平的 H2O2 时表现出敏感性增加，同时 katA 的转录水平与野生型菌株相当。因此，ahpD 和 katA 的转录分别受到低浓度和高浓度 H2O2 的刺激。此外，与野生型（4.55）菌株相比，ΔahpD（3.03）和 P180-ahpD（0.47）菌株的 NAD+/NADH 比值严重降低。转录分析表明，ahpD 和上游基因，如 cg2675、cg2676、cg2677 和 cg2678，被注释为 ABC 型转运体，被组织成一个操纵子。总之，这些发现表明谷氨酸棒杆菌拥有针对过氧化氢的两级防御途径，涉及 katA 和 ahpD。此外，ahpD 以及 cg2675-cg2678 基因可能在细胞应对氧化应激的活性中发挥新的作用。
