氧化胁迫对酿酒酵母NAD(H)激酶突变体呼吸链活性的影响

The influence of oxidative stress on the respiratory chain activity of Saccharomyces cerevisiae NAD(H) kinase mutant

【目的】了解酿酒酵母线粒体NAD(H)激酶Pos5p对呼吸链活性的维持是否与其抗氧化功能有关。【方法】比较在不同类型的氧化胁迫试剂作用下,野生菌BY4742、POS5基因缺失体pos5Δ及其回补体pos5Δ/POS5-YEp的呼吸链各个酶复合体的活性变化及细胞内活性氧水平变化。【结果】在非胁迫条件下,pos5Δ的各个复合体活性明显低于BY4742,而pos5Δ/POS5-YEp的活性有所恢复,这与它们的胞内活性氧水平相一致。在甲萘醌胁迫下,BY4742和pos5Δ的各个复合体活性都发生不同程度的下降,但pos5Δ/POS5-YEp的活性都升高。在H2O2、马来酸二乙酯胁迫下,除个别复合体外,BY4742、pos5Δ和pos5Δ/POS5-YEp的呼吸链复合体活性都降低,尤以pos5Δ的活性降低最为严重,BY4742的活性降低则较少,而pos5Δ/POS5-YEp在H2O2胁迫下的活性降低得到了缓解。说明甲萘醌、H2O2和马来酸二乙酯胁迫会造成酿酒酵母呼吸链各个复合体发生损伤,而过表达Pos5p则有助于缓解甲萘醌和H2O2引起的损伤。【结论】Pos5p对呼吸链的作用与其抗氧化功能有相关性。

[Objective] To realize the relationship between respiratory maintenance and anti-oxidative function of Pos5p, the mitochondrial NAD（H） kinase in Saccharomyces cerevisiae. [Methods] The respiratory chain activity and reactive oxygen species （ROS） level of wild-type BY4742, POS5 gene deletion mutant pos5Δ, and pos5Δ containing POS5-YEplac195 plasmid （pos5Δ/POS5-YEp） under exposure to different kinds of oxidative reagents were compared. [Results] At the normal growth condition, pos5Δ exhibited poorer respiratory chain activity than that of BY4742, while pos5Δ/POS5-YEp gave the partial restored activity, consistent with the ROS level of these three strains. Under the oxidative stress of menadione, the respiratory chain activities of BY4742 and pos5Δ decreased, while that of pos5Δ/POS5-YEp increased. Under the oxidative stress of H2O2 and diethyl maleate, nearly all of the activities of BY4742, pos5Δ and pos5Δ/POS5-YEp reduced, with that of pos5Δ most seriously, and that of pos5Δ/POS5-YEp under H2O2 lessened. Thus indicated that the oxidative stress would injury the respiratory chain complex of S. cerevisiae and over-expression of Pos5p could alleviate the injury from menadione and H2O2. [Conclusion] The protecting function of Pos5p on respiratory chain was correlated to its antioxidative defense function.