Relative association of Rubisco with manganese and magnesium as a regulatory mechanism in plants
Relative association of Rubisco with manganese and magnesium as a regulatory mechanism in plants
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DOI：
10.1111/ppl.12616
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发表时间：
2017-12-01
影响因子：
6.4
通讯作者：
Kameritsch, Petra
中科院分区：
文献类型：
--
作者：
Bloom, Arnold J.;Kameritsch, Petra
Rubisco是一种酶，它构成了叶片中多达一半的蛋白质，它要么启动光呼吸途径，为硝酸盐同化为氨基酸提供还原剂，要么启动C3碳固定途径来产生碳水化合物。这两条途径的相对速率既取决于O-2和CO2占据Rubisco活性中心的相对程度，也取决于锰或镁是否与酶结合。这项研究量化了烟草叶绿体中锰和镁的活性，以及这些金属与从烟草或细菌中纯化的Rubisco结合的热力学。在烟草叶绿体中，锰的活性低于镁，但从烟草中纯化的Rubisco对锰的亲和力较高。叶绿体中每种金属的活性与烟草Rubisco对每种金属的亲和力相似。这表明，在烟草叶绿体中，Rubisco几乎等量地与两种金属结合，并迅速地将一种金属交换为另一种金属。在烟草和细菌的Rubisco中，镁的结合相似，而这些物种之间的Rubisco对锰的结合有很大差异。此外，C3植物叶片中锰/镁的比值随着大气二氧化碳浓度的增加而增加。这些结果表明，Rubisco已经进化为改善光呼吸和硝酸盐同化之间的能量传递，植物调节叶绿体中的锰和镁的活性，以缓解大气CO2变化时氮/碳平衡的不利变化。
Rubisco, the enzyme that constitutes as much as half of the protein in a leaf, initiates either the photorespiratory pathway that supplies reductant for the assimilation of nitrate into amino acids or the C3 carbon fixation pathway that generates carbohydrates. The relative rates of these two pathways depend both on the relative extent to which O-2 and CO2 occupies the active site of Rubisco and on whether manganese or magnesium is bound to the enzyme. This study quantified the activities of manganese and magnesium in isolated tobacco chloroplasts and the thermodynamics of binding of these metals to Rubisco purified from tobacco or a bacterium. In tobacco chloroplasts, manganese was less active than magnesium, but Rubisco purified from tobacco had a higher affinity for manganese. The activity of each metal in the chloroplast was similar in magnitude to the affinity of tobacco Rubisco for each. This indicates that, in tobacco chloroplasts, Rubisco associates almost equally with both metals and rapidly exchanges one metal for the other. Binding of magnesium was similar in Rubisco from tobacco and a bacterium, whereas binding of manganese differed greatly between the Rubisco from these species. Moreover, the ratio of leaf manganese to magnesium in C3 plants increased as atmospheric CO2 increased. These results suggest that Rubisco has evolved to improve the energy transfers between photorespiration and nitrate assimilation and that plants regulate manganese and magnesium activities in the chloroplast to mitigate detrimental changes in their nitrogen/carbon balance as atmospheric CO2 varies.