Moustafa Hassan H, Fridovich I
J Bacteriol. 1977 Nov;132(2):505-10. doi: 10.1128/jb.132.2.505-510.1977.
Growth of Escherichia coli, based upon the fermentation of glucose, is associated with a low intracellular level of superoxide dismutase. Exhaustion of glucose, or depression of the pH due to accumulation of organic acids, causes these organisms to then obtain energy from the oxidative degradation of other substances present in a rich medium. This shift in metabolism is associated with a marked increase in the rate of synthesis of superoxide dismutase. Depression of the synthesis of superoxide dismutase by glucose is not due to catabolite repression since it is not eliminated by cyclic adenosine 3',5'-monophosphate and since alpha-methyl glucoside does not mimic the effect of glucose. Moreover, glucose itself no longer depresses superoxide dismutase synthesis when the pH has fallen low enough to cause a shift to a non-fermentative metabolism. It appears likely that superoxide dismutase is controlled directly or indirectly by the intracellular level of O2- and that glucose depressed the level of this enzyme because glucose metabolism is not associated with as rapid a production of O2- as is the metabolsim of many other substances. In accord with this view is the observation that paraquat, which can increase the rate of production of O2- by redox cycling, caused a rapid and marked increase in superoxide dismutase.
基于葡萄糖发酵的大肠杆菌生长与细胞内超氧化物歧化酶水平较低有关。葡萄糖耗尽，或由于有机酸积累导致pH值降低，会使这些微生物从富含培养基中存在的其他物质的氧化降解中获取能量。这种代谢转变与超氧化物歧化酶合成速率的显著增加有关。葡萄糖对超氧化物歧化酶合成的抑制并非由于分解代谢物阻遏，因为它不会被环腺苷3',5'-单磷酸消除，且α-甲基葡萄糖苷也不会模拟葡萄糖的作用。此外，当pH值降低到足以导致向非发酵代谢转变时，葡萄糖本身不再抑制超氧化物歧化酶的合成。超氧化物歧化酶似乎直接或间接受细胞内O2-水平的控制，葡萄糖降低了这种酶的水平，因为葡萄糖代谢不像许多其他物质的代谢那样与O2-的快速产生相关。与此观点一致的是，百草枯可通过氧化还原循环增加O2-的产生速率，导致超氧化物歧化酶迅速且显著增加。
