Dimroth P, Thomer A
Institut für Physiologische Chemie der Technischen Universität München, Federal Republic of Germany.
Arch Microbiol. 1989;151(5):439-44. doi: 10.1007/BF00416604.
Membranes of Klebsiella pneumoniae, grown anaerobically on citrate, contain a NADH oxidase activity that is activated specifically by Na+ or Li+ ions and effectively inhibited by 2-heptyl-4-hydroxyquinoline-N-oxide (HQNO). Cytochromes b and d were present in the membranes, and the steady state reduction level of cytochrome b increased on NaCl addition. Inverted bacterial membrane vesicles accumulated Na+ ions upon NADH oxidation. Na+ uptake was completely inhibited by monensin and by HQNO and slightly stimulated by carbonylcyanide-p-trifluoromethoxy phenylhydrazone (FCCP), thus indicating the operation of a primary Na+ pump. A Triton extract of the bacterial membranes did not catalyze NADH oxidation by O2, but by ferricyanide or menadione in a Na+-independent manner. The Na+-dependent NADH oxidation by O2 was restored by adding ubiquinone-1 in micromolar concentrations. After inhibition of the terminal oxidase with KCN, ubiquinol was formed from ubiquinone-1 and NADH. The reaction was stimulated about 6-fold by 10 mM NaCl and was severely inhibited by low amounts of HQNO. Superoxide radicals were formed during electron transfer from NADH to ubiquinone-1. These radicals disappeared by adding NaCl, but not with NaCl and HQNO. It is suggested that the superoxide radicals arise from semiquinone radicals which are formed by one electron reduction of quinone in a Na+-independent reaction sequence and then dismutase in a Na+ and HQNO sensitive reaction to quinone and quinol. The mechanism of the respiratory Na+ pump of K. pneumoniae appears to be quite similar to that of Vibrio alginolyticus.
肺炎克雷伯菌在柠檬酸盐上厌氧生长时，其细胞膜含有一种NADH氧化酶活性，该活性被Na⁺或Li⁺离子特异性激活，并被2-庚基-4-羟基喹啉-N-氧化物（HQNO）有效抑制。细胞膜中存在细胞色素b和d，添加NaCl后细胞色素b的稳态还原水平增加。反向细菌膜囊泡在NADH氧化时积累Na⁺离子。Na⁺摄取被莫能菌素和HQNO完全抑制，并被羰基氰化物-对-三氟甲氧基苯腙（FCCP）轻微刺激，这表明存在一个初级Na⁺泵。细菌细胞膜的Triton提取物不催化O₂对NADH的氧化，但能以不依赖Na⁺的方式催化铁氰化物或甲萘醌对NADH的氧化。通过添加微摩尔浓度的泛醌-1可恢复O₂对Na⁺依赖的NADH氧化。用KCN抑制末端氧化酶后，泛醌-1和NADH形成泛醇。该反应在10 mM NaCl存在下被刺激约6倍，并被少量HQNO严重抑制。在从NADH到泛醌-1的电子转移过程中形成超氧自由基。添加NaCl后这些自由基消失，但添加NaCl和HQNO时则不然。推测超氧自由基源自半醌自由基，其在不依赖Na⁺的反应序列中由醌的单电子还原形成，然后在对醌和泛醇敏感的Na⁺和HQNO反应中发生歧化反应。肺炎克雷伯菌呼吸Na⁺泵的机制似乎与溶藻弧菌的非常相似。
