How fast can Photosystem II split water? Kinetic performance at high and low frequencies
How fast can Photosystem II split water? Kinetic performance at high and low frequencies
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DOI：
10.1007/s11120-004-7081-1
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发表时间：
2005-06-01
影响因子：
3.7
通讯作者：
Dismukes, GC
中科院分区：
文献类型：
--
作者：
Ananyev, G;Dismukes, GC
从水中释放分子氧是光合作用的普遍特征。在体内催化这一过程的酶机制的存在、速度和效率的检测受到限制。我们描述了一种基于激光的快速重复频率荧光计（FRRF），允许高度准确和快速的测量这些属性通过动力学的叶绿素-一个可变的荧光产率（Fv）在活细胞和叶的重复频率高达10 kHz。应用到检测淬灭的Fv的描述和比较闪光诱导的O-2产量数据。直接比较了Fv和O-2中由光系统II（PS II）内的O-2进化复合物（WOC）刺激初级电荷重组引起的第四周期振荡。Kok模型的酶参数的第一次定量计算（α-未命中; β-双命中; S-状态群体）从Fv数据报道，该数据在5 kHz的闪光频率范围内，比先前检查的宽100倍。比较蓝藻、绿色藻类和菠菜的几个例子表明，节旋藻属，一种在碱性碳酸盐湖泊中生长的蓝细菌，表现出有史以来最快的水分解速度，因此在活体内观察。在所有的产氧光养生物研究到目前为止，一个前所未有的大增加角α和β参数发生在高和低的闪光频率，这与它们的强相关性，表明PS II-WOC中心分裂水在显着较低的效率，并可能通过不同的机制，在这些极端的闪光频率。预计将对经典的Kok模型进行修订。
Molecular oxygen evolution from water is a universal signature of oxygenic photosynthesis. Detection of the presence, speed and efficiency of the enzymatic machinery that catalyzes this process in vivo has been limited. We describe a laser-based fast repetition rate fluorometer (FRRF) that allows highly accurate and rapid measurements of these properties via the kinetics of Chl-a variable fluorescence yield (Fv) in living cells and leaves at repetition rates up to 10 kHz. Application to the detection of quenching of Fv is described and compared to flash-induced O-2 yield data. Period-four oscillations in both Fv and O-2, caused by stimulation of primary charge recombination by the O-2 evolving complex (WOC) within Photosystem II (PS II), are directly compared. The first quantitative calculations of the enzymatic parameters of the Kok model (alpha - miss; beta - double hit; S-state populations) are reported from Fv data over a 5 kHz range of flash frequencies that is 100-fold wider than previously examined. Comparison of a few examples of cyanobacteria, green algae and spinach reveals that Arthrospira m., a cyanobacterium that thrives in alkaline carbonate lakes, exhibits the fastest water-splitting rates ever observed thus farin vivo. In all oxygenic phototrophs examined thus far, an unprecedented large increase in the Kok alpha and beta parameters occur at both high and low flash frequencies, which together with their strong correlation, indicates that PS II-WOC centers split water at remarkably lower efficiencies and possibly by different mechanisms at these extreme flash frequencies. Revisions to the classic Kok model are anticipated.