The global mass and average rate of rubisco
The global mass and average rate of rubisco
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DOI：
10.1073/pnas.1816654116
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发表时间：
2019-03-05
影响因子：
11.1
通讯作者：
Milo, Ron
中科院分区：
文献类型：
--
作者：
Bar-On, Yinon M.;Milo, Ron
光合作用的碳同化作用使能量储存在生活世界中，并产生生物圈中的大部分生物质。Rubisco（D-核酮糖1，5-二磷酸羧化酶/加氧酶）负责全球绝大多数的碳固定，并且被认为是地球上最丰富的蛋白质。在这里，我们对地球上Rubisco的总质量进行了更新和严格的估计，得出的结论是大约为0.7 Gt，比以前认为的高出一个数量级。我们发现，> 90%的Rubisco酶存在于陆地植物约2 × 10（14）m（2）的叶片中，Rubisco约占叶片总质量的3%，我们估计叶片干重约为30 Gt。我们使用我们对Rubisco总质量的估计，推导出Rubisco的有效时均催化速率，在陆地上约为0.03 s（-1），在海洋中约为0.6 s（-1）。与在25摄氏度的体外观察到的最大催化速率相比，在野外的有效速率在陆地上慢了100倍，在海洋中慢了7倍。较低的环境温度，以及Rubisco在夜间不工作，可以解释海洋中实验室条件的大部分差异，而不是陆地上，需要在全球范围内量化更多因素。我们的分析有助于加深实验室和野生环境之间以及陆地和海洋环境之间的巨大差异。
Photosynthetic carbon assimilation enables energy storage in the living world and produces most of the biomass in the biosphere. Rubisco (D-ribulose 1,5-bisphosphate carboxylase/oxygenase) is responsible for the vast majority of global carbon fixation and has been claimed to be the most abundant protein on Earth. Here we provide an updated and rigorous estimate for the total mass of Rubisco on Earth, concluding it is approximate to 0.7 Gt, more than an order of magnitude higher than previously thought. We find that > 90% of Rubisco enzymes are found in the approximate to 2 x 10(14) m(2) of leaves of terrestrial plants, and that Rubisco accounts for approximate to 3% of the total mass of leaves, which we estimate at approximate to 30 Gt dry weight. We use our estimate for the total mass of Rubisco to derive the effective time-averaged catalytic rate of Rubisco of approximate to 0.03 s(-1) on land and approximate to 0.6 s(-1) in the ocean. Compared with the maximal catalytic rate observed in vitro at 25 degrees C, the effective rate in the wild is approximate to 100-fold slower on land and sevenfold slower in the ocean. The lower ambient temperature, and Rubisco not working at night, can explain most of the difference from laboratory conditions in the ocean but not on land, where quantification of many more factors on a global scale is needed. Our analysis helps sharpen the dramatic difference between laboratory and wild environments and between the terrestrial and marine environments.