Rubiscolytics: fate of Rubisco after its enzymatic function in a cell is terminated
Rubiscolytics: fate of Rubisco after its enzymatic function in a cell is terminated
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DOI：
10.1093/jxb/erm242
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发表时间：
2008-05-01
影响因子：
6.9
通讯作者：
Mae, Tadahiko
中科院分区：
文献类型：
--
作者：
Feller, Urs;Anders, Iwona;Mae, Tadahiko
核酮糖-1，5-二磷酸羧基/加氧酶(Rubisco)是植物光合作用部位的主要蛋白质，也是地球上含量最丰富的蛋白质。在衰老过程中，其净降解产生的氨基酸被输送到汇(如发育中的叶子、果实)。Rubisco的分解代谢并不仅受总体下沉需求的控制。在某些条件下，碳水化合物的积累也可能加速衰老和Rubisco的降解。蛋白质分解产生的氨基酸在具有适当源-库关系的植物中迅速重新分布。在库容量降低的小麦植株的叶片中(例如，库移走，叶基蒸汽环剥造成韧皮部中断)，Rubisco被降解，游离氨基酸积累。在衰老后期，它们可能会被雨水冲走。在豆荚大豆的叶片中，Rubisco被降解，氨基酸可以在这些叶片中被重新利用，用于在脉旁叶肉中合成特殊的液泡蛋白(营养贮藏蛋白)。一年生作物老叶(衰老)中Rubisco降解产生的氮素在一定程度上重新整合到幼叶或果实的光合作用组织中新合成的Rubisco中。最后，很高比例的氮积累在蛋白质体内(贮藏蛋白质)。在亚细胞水平上，Rubisco可以在完整的叶绿体中被降解。活性氧可以直接裂解大亚基或对其进行修饰，使其更容易发生蛋白质降解。金属内肽酶可能在完整叶绿体中Rubisco的降解过程中发挥重要作用。此外，不同的实验室推测，液泡内肽酶(S)参与了Rubisco的分解代谢(至少在一定条件下)。
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the predominant protein in photosynthesizing plant parts and the most abundant protein on earth. Amino acids deriving from its net degradation during senescence are transported to sinks (e.g. developing leaves, fruits). Rubisco catabolism is not controlled only by the overall sink demand. An accumulation of carbohydrates may also accelerate senescence and Rubisco degradation under certain conditions. Amino acids produced by proteolysis are rapidly redistributed in plants with proper source-sink relationships. In leaves of wheat plants with reduced sink capacity (e.g. sink removal, phloem interruption by steam girdling at the leaf base), Rubisco is degraded and free amino acids accumulate. They may be washed out in the rain during late senescence. In leaves of depodded soybeans, Rubisco is degraded and amino acids can be reutilized in these leaves for the synthesis of special vacuolar proteins in the paraveinal mesophyll (vegetative storage proteins). Nitrogen deriving from Rubisco degradation in older (senescing) leaves of annual crops is integrated to some extent again in newly synthesized Rubisco in younger leaves or photosynthesizing tissues of fruits. Finally, a high percentage of this nitrogen is accumulated in protein bodies (storage proteins). At the subcellular level, Rubisco can be degraded in intact chloroplasts. Reactive oxygen species may directly cleave the large subunit or modify it to become more susceptible to proteolysis. A metalloendopeptidase may play an important role in Rubisco degradation within intact chloroplasts. Additionally, the involvement of vacuolar endopeptidase(s) in Rubisco catabolism (at least under certain conditions) was postulated by various laboratories.