Department of Biochemistry, University of California, Riverside, CA 92521-0129, USA.
J Exp Bot. 2013 Jan;64(2):433-43. doi: 10.1093/jxb/ers330. Epub 2012 Nov 16.
L-Ascorbic acid (Asc) is the most abundant water-soluble antioxidant in plants. It serves as a cofactor for enzymes involved in photosynthesis, hormone biosynthesis, and the regeneration of antioxidants such as α-tocopherol. Once used, Asc can be recycled by several different mechanisms. The short-lived monodehydroascorbate (MDHA) radical, produced following Asc oxidation, can be recycled following reduction by ferredoxin or monodehydroascorbate reductase (MDAR). MDHA can also undergo disproportionation into dehydroascorbate (DHA) and Asc. DHA can be recycled into Asc by dehydroascorbate reductase (DHAR) before it undergoes irrevocable hydrolysis. Through its recycling, Asc content and its redox state are maintained, which is critical under conditions of high demand, for example during high light or other stress conditions that increase reactive oxygen species (ROS) production. This review provides an overview of research in the last decade revealing the role that Asc recycling plays during germination, growth, and reproduction, as well as in response to environmental stress. These findings highlight the importance of DHAR- and MDAR-mediated mechanisms of Asc recycling in maintaining ROS at non-damaging levels while modulating ROS signalling function.
L-抗坏血酸(Asc)是植物中最丰富的水溶性抗氧化剂。它作为参与光合作用、激素生物合成以及α-生育酚等抗氧化剂再生的酶的辅助因子。一旦被使用,Asc 可以通过几种不同的机制进行回收。短寿命的单脱氢抗坏血酸(MDHA)自由基,在 Asc 氧化后产生,可以通过铁氧还蛋白或单脱氢抗坏血酸还原酶(MDAR)还原进行回收。MDHA 也可以通过歧化作用转化为脱氢抗坏血酸(DHA)和 Asc。DHA 可以在不可逆水解之前通过脱氢抗坏血酸还原酶(DHAR)转化回 Asc。通过其回收,维持了 Asc 的含量及其氧化还原状态,这在高需求条件下至关重要,例如在高光或其他增加活性氧(ROS)产生的胁迫条件下。这篇综述概述了过去十年的研究结果,揭示了 Asc 回收在发芽、生长和繁殖以及对环境胁迫的反应中所起的作用。这些发现强调了 DHAR 和 MDAR 介导的 Asc 回收机制在维持非破坏性 ROS 水平的同时调节 ROS 信号功能方面的重要性。