Search for chlorophyll degradation enzyme, Mg-dechelatase, from extracts of Chenopodium album with native and artificial substrates
Search for chlorophyll degradation enzyme, Mg-dechelatase, from extracts of Chenopodium album with native and artificial substrates
复制标题
DOI：
10.1016/j.plantsci.2005.03.010
复制
发表时间：
2005-07-01
期刊：
影响因子：
5.2
通讯作者：
Shioi, Y
中科院分区：
文献类型：
--
作者：
Kunieda, T;Amano, T;Shioi, Y
在叶绿素 (Ch1) 降解的早期步骤中，叶绿素 a (Chlide) 经镁脱螯合生成脱镁叶绿酸已知是由所谓的镁脱螯合酶催化的。我们之前证明，使用氯化物作为天然底物的镁脱螯合反应需要较小的金属螯合物质（MCS）的存在。这项研究进一步证实了这一点，其中使用人工底物 Mg-叶绿素 a (Chlin) 和天然底物 Chlide，在凝胶过滤色谱法后以完整级分检查了藜成熟叶提取物中的镁脱螯合活性。当 Chlin 用作底物时，存在小分子量 MCS 和 M 释放蛋白 (MRP)。然而，只有 MCS 对天然底物具有 Mg 脱螯合活性。除了先前已知的过氧化物酶 (POD) 之外，谷胱甘肽 S-转移酶 (GST) 被确定为镁释放蛋白之一。在不存在 MRP 的情况下，添加低浓度的过氧化氢后，观察到 Chlin 自发释放 Mg，但 Chlide 则没有。这些发现表明，MCS 在 Ch1 分解途径中镁脱螯合反应的催化中发挥作用。 MRP 从 Chlin 中释放 Mg 可能与过氧化氢等活性氧的功能有关。讨论了与天然基质相比，人工基质的镁释放和分子可塑性之间的关系。 (c) 2005 Elsevier Ireland Ltd. 保留所有权利。
In the early steps of chlorophyll (Ch1) degradation, the Mg-dechelation of chlorophyllide a (Chlide) to pheophorbide is known to be catalyzed by the so-called Mg-dechelatase. We previously demonstrated that the presence of a smaller metal-chelating substance (MCS) is required for the Mg-dechelation reaction using Chlide as the native substrate. This was further substantiated by this study in which Mg-dechelation activity in extracts from mature leaves of Chenopodium album was examined in complete fractions after gel filtration chromatography using an artificial substrate, Mg-chlorophyllin a (Chlin) and the native substrate, Chlide. A small-molecular-weight MCS and M-releasing proteins (MRPs) were present when Chlin was used as the substrate. However, only MCS had Mg-dechelation activity for the native substrate. Glutathione S-transferase (GST) was identified as one of the Mg-releasing proteins in addition to the previously known peroxidase (POD). Spontaneous release of Mg from Chlin was observed after the addition of a low concentration of hydrogen peroxide in the absence of MRPs, but not Chlide. These findings demonstrate that MCS plays a role in the catalysis of the Mg-dechelation reaction in the breakdown pathway of Ch1. The release of Mg from Chlin by MRP may relate to the function of active oxygen species such as hydrogen peroxide. The relationship between Mg-release and the molecular plasticity of the artificial substrate compared to native substrate is discussed. (c) 2005 Elsevier Ireland Ltd. All rights reserved.