Institute for Multidisciplinary Research, University of Belgrade, Belgrade, Serbia.
Carbohydr Res. 2011 Oct 18;346(14):2255-9. doi: 10.1016/j.carres.2011.07.015. Epub 2011 Jul 24.
Oxidative burst in plants is elicited by biotic and abiotic stressors. Analogously to some monosaccharides which act as intracellular antioxidants, cell-wall polysaccharides may be in charge of buffering free-radical production in the extracellular compartment under pronounced prooxidative settings. Although a wide range of plant polysaccharides have been examined for their antioxidative properties, this usually has not been done in a coherent and comparative manner and against biologically relevant reactive species. Here we show that different cell-wall polysaccharides, cellulose, pectin, D-galacto-D-mannan, arabinogalactan, and xylan, exhibit distinctive antioxidative activities against the hydroxyl radical (·OH)-generating Fenton reaction and superoxide. We found, using an EPR spin-trapping method, that the main carriers of 'anti-Fenton' activity in the plant cell wall are pectin and xylan. They most likely act by binding metal ions in such a manner to allow the Fenton reaction, after which they scavenge ·OH. Such a mode of action is preferred by cells resulting in a safe degradation of H(2)O(2). On the other hand, the polysaccharides examined showed similar superoxide scavenging capacities. We propose that plants may employ different antioxidative characteristics of polysaccharides to regulate their redox status by modifying the composition of the cell wall.
植物的氧化爆发是由生物和非生物胁迫引起的。类似于一些作为细胞内抗氧化剂的单糖，细胞壁多糖可能负责在明显的促氧化环境下缓冲细胞外区室中自由基的产生。尽管已经对多种植物多糖的抗氧化特性进行了研究，但通常没有以一致和可比的方式进行，也没有针对生物学上相关的反应性物质进行研究。在这里，我们表明，不同的细胞壁多糖，纤维素、果胶、D-半乳糖-D-甘露聚糖、阿拉伯半乳聚糖和木聚糖，对芬顿反应和超氧自由基产生的羟基自由基（·OH）具有独特的抗氧化活性。我们使用 EPR 自旋捕获方法发现，植物细胞壁中“抗芬顿”活性的主要载体是果胶和木聚糖。它们很可能通过以这种方式结合金属离子来允许芬顿反应，之后它们会清除·OH。这种作用模式是细胞所偏好的，导致 H（2）O（2）的安全降解。另一方面，所检查的多糖具有相似的超氧自由基清除能力。我们提出，植物可能通过改变细胞壁的组成来利用多糖的不同抗氧化特性来调节其氧化还原状态。
