Gardner P R, Costantino G, Salzman A L
Division of Critical Care Medicine, Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA. gardpo0chmcc.org
J Biol Chem. 1998 Oct 9;273(41):26528-33. doi: 10.1074/jbc.273.41.26528.
Nitric oxide (NO.) is a naturally occurring toxin that some organisms adaptively resist. In aerobic or anaerobic Escherichia coli, low levels of NO. exposure inactivated the NO.-sensitive citric acid cycle enzyme aconitase, and inactivation was more effective when the adaptive synthesis of NO.-defensive proteins was blocked with chloramphenicol. Protection of aconitase in aerobically grown E. coli was dependent upon O2, was potently inhibited by cyanide, and was correlated with an induced rate of cellular NO. consumption. Constitutive and adaptive cellular NO. consumption in aerobic cells was also dependent upon O2 and inhibited by cyanide. Exposure of aerobic cells to NO. accordingly elevated the activity of the O2-dependent and cyanide-sensitive NO. dioxygenase (NOD). Anaerobic E. coli exposed to NO. or nitrate induced a modest O2-independent and cyanide-resistant NO.-metabolizing activity and a more robust O2-stimulated cyanide-sensitive activity. The latter activity was attributed to NOD. The results support a role for NOD in the aerobic detoxification of NO. and suggest functions for NOD and a cyanide-resistant NO. scavenging activity in anaerobic cells.
一氧化氮（NO.）是一种天然存在的毒素，一些生物能对其产生适应性抵抗。在需氧或厌氧的大肠杆菌中，低水平的NO.暴露会使对NO.敏感的柠檬酸循环酶乌头酸酶失活，当用氯霉素阻断NO.防御蛋白的适应性合成时，失活效果更明显。在需氧生长的大肠杆菌中，乌头酸酶的保护作用依赖于O2，能被氰化物强烈抑制，且与细胞消耗NO.的诱导速率相关。需氧细胞中组成型和适应性细胞消耗NO.也依赖于O2，并被氰化物抑制。因此，将需氧细胞暴露于NO.会提高依赖O2且对氰化物敏感的NO.双加氧酶（NOD）的活性。暴露于NO.或硝酸盐的厌氧大肠杆菌诱导出适度的不依赖O2且对氰化物有抗性的NO.代谢活性以及更强的受O2刺激且对氰化物敏感的活性。后一种活性归因于NOD。这些结果支持了NOD在需氧条件下对NO.进行解毒的作用，并暗示了NOD以及厌氧细胞中一种对氰化物有抗性的NO.清除活性的功能。
