METHIONINE SULFOXIDE REDUCTASE

甲硫氨酸亚硫酸还原酶

• 批准号: 6162642
• 负责人: J M POSTON
• 金额: --
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6162642
• 关键词: Escherichia coli; age difference; aging; antioxidants; electron transport; enzyme activity; free radical oxygen; laboratory rat; miscellaneous oxidoreductase; oxidative stress; protein metabolism; protein purification

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 have shown that activity of this enzyme in Fisher 344 rats gradually, although not dramatically, declines with age. It has been shown, also, that the enzyme is widely distributed, being found in Escherichia coli, Saccharomyces cerevisiae, beef liver, and human cells (cell culture). The S. cerevisiae gene has been cloned and inserted in a plasmid which permits over-production of the enzyme. When the a mutant, lacking methionine sulfoxide reductase, is given the plasmid containing the gene, the phenotype resembles wild-type yeast. Like the enzyme activity in E. coli, the yeast activity is most vigorously expressed in late log and stationary phase cultures. This expression seems consistent with the idea that damaged methionines may be most prevalent and in need of repair when the cells have been exposed the longest to oxygen. The Km for protein-bound methionine sulfoxide (using the model compound, N-DABSYL-sulfoxide) is in the micromolar range: 15.3 for yeast, 31.8 for beef, and 120 for E. coli.

蛋白质暴露在氧气中，尤其是暴露在还原氧中 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 分析表明，这种酶的活性在 Fisher 344大鼠随着年龄的增长而逐渐下降，但并不显著。 它已被证明，而且，酶是广泛分布， 发现于大肠杆菌、酿酒酵母、牛肝和 人类细胞（细胞培养）。 色葡萄酿酒酵母基因已被克隆， 插入允许酶过量产生的质粒中。 当 缺乏甲硫氨酸亚砜还原酶的突变体， 质粒含有该基因，表型类似于野生型酵母。 与E. coli中，酵母活性最高 在对数生长后期和稳定期培养物中强烈表达。 这 表达似乎与受损的甲硫氨酸可能 当细胞暴露在空气中时， 最长的氧气。 蛋白结合蛋氨酸亚砜的Km （使用模型化合物，N-DABSYL-亚砜）是在微摩尔 范围：酵母15.3，牛肉31.8，大肠杆菌120。杆菌