The FAD-enzyme monodehydroascorbate radical reductase mediates photoproduction of superoxide radicals in spinach thylakoid membranes
The FAD-enzyme monodehydroascorbate radical reductase mediates photoproduction of superoxide radicals in spinach thylakoid membranes
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DOI：
10.1093/oxfordjournals.pcp.a029440
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发表时间：
1998-08-01
影响因子：
4.9
通讯作者：
Asada, K
中科院分区：
文献类型：
--
作者：
Miyake, C;Schreiber, U;Asada, K
1 μM 的 FAD 酶单脱氢抗坏血酸自由基 (MDA) 还原酶将菠菜类囊体膜中双氧的光还原增强约 10 倍。MDA 还原酶催化双氧的主要光还原产物是超氧自由基，超氧化物歧化酶对 Cyt c 光还原的抑制证明了这一点。 MDA还原酶依赖性分子氧光还原的分子氧表观K-m为100μM，比仅用类囊体膜观察到的高一个数量级。谷胱甘肽还原酶、铁氧还蛋白-NADP(+)还原酶和乙醇酸氧化酶也介导类囊体膜中超氧自由基的光产生，其速率与MDA还原酶相似。在这些黄素酶中，MDA 还原酶是最有可能刺激叶绿体中双氧光还原的介质；讨论了其在过量光照下防止光抑制的功能。
The photoreduction of dioxygen in spinach thylakoid membranes was enhanced about 10-fold by the FAD-enzyme monodehydroascorbate radical (MDA) reductase at 1 mu M. The primary photoreduced product of dioxygen catalyzed by MDA reductase was the superoxide radical, as evidenced by the inhibition of photoreduction of Cyt c by superoxide dismutase. The apparent K-m for dioxygen of the MDA reductase-dependent photoreduction of dioxygen was 100 mu M, higher by one order of magnitude than that observed with thylakoid membranes only. Glutathione reductase, ferredoxin-NADP(+) reductase, and glycolate oxidase also mediated the photoproduction of superoxide radicals in thylakoid membranes at rates similar to those with MDA reductase. Among these flavoenzymes, MDA reductase is the most likely mediator stimulating the photoreduction of dioxygen in chloroplasts; its function in the protection from photoinhibition under excess light is discussed.