METHIONINE SULFOXIDE REDUCTASE

蛋白质暴露于氧气，特别是还原氧 化合物，如过氧化氢和羟基自由基， 蛋白质分子上敏感位点的氧化。 敏感 位点，蛋氨酸的硫特别容易受到攻击。 一个 甲硫氨酸亚砜还原酶可以逆转这种氧化， 它已经被证明是一个球员在持续修复氧化 受损蛋白质 对这种酶的分析表明， 稳定的，如果不是戏剧性的，在增加的大鼠肝脏活性的损失， 年龄，在24个月时下降到2个月时的80%。 这些发现表明，衰老的影响之一是减少 修复受损酶的能力。 不同的提取物的调查 器官显示，该酶活性在大鼠体内广泛分布 在肾脏中的活性最高 有关分派 支持这一假设，即酶是重要的，在维护 的细胞。 肾脏中的高水平活性可能代表 酶在回收氧化的甲硫氨酸中的用途， 节省了对替代来源的营养需求。 蛋氨酸 亚砜还原酶已从大肠杆菌中纯化。 而 在E.大肠杆菌在生长过程中， 水平在稳定期急剧上升。

Exposure of proteins to oxygen and, especially, to reduced oxygen compounds, such as hydrogen peroxide and hydroxyl radical, permits the oxidation of sensitive sites on the protein molecules. Of the sensitive sites, the sulfur of methionine is particularly subject to attack. An enzyme, methionine sulfoxide reductase, can reverse this oxidation and it has been shown to be a player in the continuing repair of oxidatively damaged proteins. Assays for this enzyme have shown that there is a steady, if undramatic, loss in activity in livers of rats of increasing age, falling at 24 months to values 80 percent of those at 2 months. These findings suggest that one of the effects of aging is decreased ability to repair damaged enzymes. Surveys of extracts of different organs show that the enzyme activity is widely distributed in the rat with the greatest activity found in the kidney. Such distribution supports the hypothesis that the enzyme is important in the maintenance of the cell. The high level of activity in the kidney may represent the utility of the enzyme in reclaiming oxidized methionine and thereby sparing the nutritional demands for replacement sources. Methionine sulfoxide reductase has been purified from Escherichia coli. Whereas there is a low level of activity in cultures of E. coli during growth, the levels rise dramatically in stationary phase.