Yamashiro Takumi, Murata Kousaku, Kawai Shigeyuki
Laboratory of Basic and Applied Molecular Biotechnology, Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto, 611-0011, Japan.
Faculty of Science and Engineering, Department of Life Science, Setsunan University, Neyagawa, Osaka, Japan.
Extremophiles. 2017 Mar;21(2):399-407. doi: 10.1007/s00792-016-0913-z. Epub 2017 Jan 12.
Deinococcus radiodurans is highly resistant to ionizing radiation and UV radiation, and oxidative stress caused by such radiations. NADP(H) seems to be important for this resistance (Slade and Radman, Microbiol Mol Biol Rev 75:133-191; Slade, Radman, Microbiol Mol Biol Rev 75:133-191, 2011), but the mechanism underlying the generation of NADP(H) or NAD(H) in D. radiodurans has not fully been addressed. Intracellular concentrations of NAD, NADH, NADP, and NADPH in D. radiodurans are also not determined yet. We found that cell extracts of D. radiodurans catalyzed reduction of NAD(P) in vitro, indicating that D. radiodurans cells contain both enzymes and a high concentration of substrates for this activity. The enzyme and the substrate were attributed to glucose-6-phosphate dehydrogenase and glucose-6-phosphate of which intracellular concentration was extremely high. Unexpectedly, the intracellular concentration of NAD(H) was also much greater than that of NADP(H), suggesting some significant roles of NADH. These unusual features of this bacterium would shed light on a new aspect of physiology of this bacterium.
耐辐射球菌对电离辐射、紫外线辐射以及此类辐射引起的氧化应激具有高度抗性。NADP(H) 似乎对这种抗性很重要（斯莱德和拉德曼，《微生物学与分子生物学评论》75:133 - 191；斯莱德、拉德曼，《微生物学与分子生物学评论》75:133 - 191，2011），但耐辐射球菌中NADP(H) 或NAD(H) 的产生机制尚未完全阐明。耐辐射球菌细胞内NAD、NADH、NADP和NADPH的浓度也尚未确定。我们发现耐辐射球菌的细胞提取物在体外催化NAD(P) 的还原，这表明耐辐射球菌细胞含有该活性的酶和高浓度的底物。该酶和底物分别为葡萄糖 - 6 - 磷酸脱氢酶和细胞内浓度极高的葡萄糖 - 6 - 磷酸。出乎意料的是，NAD(H) 的细胞内浓度也远高于NADP(H)，这表明NADH具有一些重要作用。这种细菌的这些不寻常特征将为该细菌生理学的一个新方面提供线索。
