Yanykin Denis V, Khorobrykh Andrei A, Khorobrykh Sergey A, Klimov Vyacheslav V
Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, Russia.
Biochim Biophys Acta. 2010 Apr;1797(4):516-23. doi: 10.1016/j.bbabio.2010.01.014. Epub 2010 Jan 25.
Oxygen consumption in Mn-depleted photosystem II (PSII) preparations under continuous and pulsed illumination is investigated. It is shown that removal of manganese from the water-oxidizing complex (WOC) by high pH treatment leads to a 6-fold increase in the rate of O(2) photoconsumption. The use of exogenous electron acceptors and donors to PSII shows that in Mn-depleted PSII preparations along with the well-known effect of O(2) photoreduction on the acceptor side of PSII, there is light-induced O(2) consumption on the donor side of PSII (nearly 30% and 70%, respectively). It is suggested that the light-induced O(2) uptake on the donor side of PSII is related to interaction of O(2) with radicals produced by photooxidation of organic molecules. The study of flash-induced O(2) uptake finds that removal of Mn from the WOC leads to O(2) photoconsumption with maximum in the first flash, and its yield is comparable with the yield of O(2) evolution on the third flash measured in the PSII samples before Mn removal. The flash-induced O(2) uptake is drastically (by a factor of 1.8) activated by catalytic concentration (5-10microM, corresponding to 2-4 Mn per RC) of Mn(2+), while at higher concentrations (>100microM) Mn(2+) inhibits the O(2) photoconsumption (like other electron donors: ferrocyanide and diphenylcarbazide). Inhibitory pre-illumination of the Mn-depleted PSII preparations (resulting in the loss of electron donation from Mn(2+)) leads to both suppression of flash-induced O(2) uptake and disappearance of the Mn-induced activation of the O(2) photoconsumption. We assume that the light-induced O(2) uptake in Mn-depleted PSII preparations may reflect not only the negative processes leading to photoinhibition but also possible participation of O(2) or its reactive forms in the formation of the inorganic core of the WOC.
研究了在连续光照和脉冲光照下，锰缺乏的光系统II（PSII）制剂中的氧气消耗情况。结果表明，通过高pH处理从水氧化复合物（WOC）中去除锰会导致O₂光消耗速率增加6倍。对PSII使用外源电子受体和供体表明，在锰缺乏的PSII制剂中，除了众所周知的PSII受体侧O₂光还原作用外，PSII供体侧也存在光诱导的O₂消耗（分别约为30%和70%）。研究表明，PSII供体侧的光诱导O₂摄取与O₂与有机分子光氧化产生的自由基的相互作用有关。对闪光诱导的O₂摄取的研究发现，从WOC中去除锰会导致O₂光消耗，在第一次闪光时达到最大值，其产量与去除锰之前PSII样品中第三次闪光时的O₂释放产量相当。闪光诱导的O₂摄取被催化浓度（5 - 10μM，对应每个反应中心2 - 4个锰）的Mn²⁺显著激活（激活因子为1.8），而在较高浓度（>100μM）时，Mn²⁺会抑制O₂光消耗（与其他电子供体：亚铁氰化物和二苯基卡巴腙类似）。对锰缺乏的PSII制剂进行抑制性预光照（导致Mn²⁺失去电子供体作用）会导致闪光诱导的O₂摄取受到抑制，以及Mn²⁺诱导的O₂光消耗激活作用消失。我们认为，锰缺乏的PSII制剂中的光诱导O₂摄取不仅可能反映导致光抑制的负面过程，还可能反映O₂或其活性形式在WOC无机核心形成中的可能参与。
