Controls on the Biosynthesis of Superoxide Dismutases in E. coli: An Inactive Precursor

大肠杆菌能产生两种类型的超氧化物 歧化酶 其中之一，铁酶在两种 好氧和厌氧培养;而第二，锰 酶，通常只存在于需氧培养物中， 可由高氧或紫精强烈诱导， 介导细胞内产生O2-的醌类。 的 细胞控制生物合成的方式 锰酶已经在研究中，但还没有 明白 本实验室报告称， 电子汇，如百草枯加硝酸盐，以厌氧 培养导致锰酶的产生， 它不是活性的，但可以通过加入 Mn（II）在轻度变性条件下;然后 去除变性应力。 这被称为 前酶 研究还表明，厌氧细胞 含有另一种可被抗体识别的蛋白质 锰酶特异性，但不能 酶原也被激活 这种蛋白质被称为 这是前原酶。 实验正在进行中 分离、表征和研究 这些形式的含锰超氧化物歧化酶 大肠大肠杆菌% 超氧化物歧化酶（SOD）是提供 生物体内的氧分子的毒性 细胞 它还可以防止其他压力，例如，超 紫外线辐射和二氧化硫暴露。 如何将这些 酶是如何产生的还不完全清楚，但很重要。 其生物合成可能受环境因素的调控 因素 本项目将阐明酶的作用途径 合成和活化。*//

Escherichia coli can produce two types of superoxide dismutases. One of these, the iron enzyme is found in both aerobic and anaerobic cultures; while the second, a manganese enzyme, is ordinarily present only in aerobic cultures and can be strongly induced by hyperoxia, or by viologens and quinones which mediate intracellular production of O2-. The manner in which the cell controls the biosynthesis of the manganese enzyme has been under study but is not yet understood. This lab has reported that addition of an electron sink, such as paraquat plus nitrate, to an anaerobic culture causes production of the manganese enzyme in a form which is not active but which can be activated by addition of Mn(II) under mildly denaturing conditions; followed by removal of the denaturing stress. This is referred to as the pro-enzyme. It has also been shown that anaerobic cells contain another protein which is recognized by an antibody specific for the manganese enzyme, but which cannot be activated as can the pro-enzyme. This protein is referred to this as the prepro-enzyme. Experiments are being conducted to isolate, characterize and study the interconversions of these forms of the manganese-containing superoxide dismutase of E. coli.%%% Superoxide dismutases (SODs) are enzymes that provide defenses against the toxicity of molecular oxygen in living cells. It also protects against other stresses, e.g., ultra- violet radiation and sulfur dioxide exposure. How these enzymes are made is incompletely understood but important. The biosynthesis is probably regulated by environmental factors. This project will elucidate the pathway of enzyme synthesis and activation.***//