A mechanism for water splitting and oxygen production in photosynthesis
A mechanism for water splitting and oxygen production in photosynthesis
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DOI：
10.1038/nplants.2017.41
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发表时间：
2017-04-01
期刊：
影响因子：
18
通讯作者：
Barber, James
中科院分区：
文献类型：
--
作者：
Barber, James
光合生物吸收阳光并将其转化为化学能。这个过程的核心是地球上最基本的反应，光驱动水分解成其元素成分。以这种方式释放分子氧，维持有氧大气并形成臭氧层。释放出的氢被用来将二氧化碳转化为构成生命的有机分子，也是化石燃料的来源。这些有机分子的氧化，无论是通过呼吸还是燃烧，都会导致储存的氢与氧重新结合，释放能量并重整水。这种水分解是通过光系统II（PSII）酶实现的。它的出现至少在30亿年前，并通过电子传递链连接到光系统I，直接导致了真核生物和多细胞生物的出现。在此之前，生物有机体一直依赖于氢/电子供体，如H2S，NH3，有机酸和Fe 2+，与液态水的海洋相比，它们的供应有限。然而，在PSII出现之前，水可能也被用作氢源，正如今天在厌氧原核生物中发现的那样，它们使用一氧化碳作为能量来源来分解水。催化该反应的酶是一氧化碳脱氢酶（CODH）。PSII和含铁和镍的这种酶（Fe-Ni CODH）的形式之间的相似性表明光合O-O键形成的可能机制。
Sunlight is absorbed and converted to chemical energy by photosynthetic organisms. At the heart of this process is the most fundamental reaction on Earth, the light-driven splitting of water into its elemental constituents. In this way molecular oxygen is released, maintaining an aerobic atmosphere and creating the ozone layer. The hydrogen that is released is used to convert carbon dioxide into the organic molecules that constitute life and were the origin of fossil fuels. Oxidation of these organic molecules, either by respiration or combustion, leads to the recombination of the stored hydrogen with oxygen, releasing energy and reforming water. This water splitting is achieved by the enzyme photosystem II (PSII). Its appearance at least 3 billion years ago, and linkage through an electron transfer chain to photosystem I, directly led to the emergence of eukaryotic and multicellular organisms. Before this, biological organisms had been dependent on hydrogen/electron donors, such as H2S, NH3, organic acids and Fe2+, that were in limited supply compared with the oceans of liquid water. However, it is likely that water was also used as a hydrogen source before the emergence of PSII, as found today in anaerobic prokaryotic organisms that use carbon monoxide as an energy source to split water. The enzyme that catalyses this reaction is carbon monoxide dehydrogenase (CODH). Similarities between PSII and the iron-and nickel-containing form of this enzyme (Fe-Ni CODH) suggest a possible mechanism for the photosynthetic O-O bond formation.