Oxygen reduction in a plastoquinone pool of isolated pea thylakoids
Oxygen reduction in a plastoquinone pool of isolated pea thylakoids
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DOI：
10.1023/a:1015583502345
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发表时间：
2002-01-01
影响因子：
3.7
通讯作者：
Ivanov, BN
中科院分区：
文献类型：
--
作者：
Khorobrykh, SA;Ivanov, BN
研究了2-碘-4-硝基百里香酚的b(6)/f-二硝基苯醚(DNP-INT)对豌豆类囊体的氧吸收作用。在没有DNP-INT的情况下，氧摄取速率在pH 5.0时有一个明显的最大值，然后下降到pH 6.5，然后缓慢上升，而在有抑制剂存在的情况下，从pH从4.5增加到6.5，然后保持接近于在没有pH 8.5的情况下的速率。在没有DNP-INT的情况下，Gramiidin D对摄氧率有很大的影响，而在DNP-INT存在的情况下，影响很小。这些差异表明，在细胞色素复合体之前的光合作用电子传递链上存在特殊的氧还原位点(S)。光系统II(BBY-颗粒)膜碎片的吸氧量较低，且不受pH的影响。这不支持Q B参与DNP INT处理的类囊体氧还原。在整个pH范围内，DCMU和过氧化氢酶都抑制类囊体在DNP-INT存在下的氧摄取。过氧化氢酶效应表明，氧摄取是水中电子对氧的还原作用的结果，而过氧化氢是这种还原的最终产物。在DNP-INT存在下，细胞色素c的光还原被超氧化物歧化酶(SOD)部分抑制，这表明超氧化物的形成。后者被抗坏血酸存在时氧摄取速率的升高和超氧化物歧化酶的抑制所证实。这两个测试都表明，可检测到的超氧自由基平均占潜在形成的超氧自由基的20%-25%，其数量是根据氧摄取率计算出来的。所获得的数据表明，氧还原发生在塑料对苯二酚池中，主要发生在膜内，在膜内，超氧化物可以在伴随的反应中被消耗。提出了一种在类囊体膜中的质醌池中进行氧还原的方案。
Oxygen uptake in isolated pea thylakoids in the presence of an inhibitor of plastoquinol oxidation by b(6)/f-complex dinitrophenylether of 2-iodo-4-nitrothymol (DNP-INT) was studied. The rate of oxygen uptake in the absence of DNP-INT had a distinct maximum at pH 5.0 followed by a decline to pH 6.5 and posterior slow rise, while in the presence of an inhibitor it increased at an increasing pH from 4.5 to 6.5 and then kept close to the rate in its absence up to pH 8.5. Gramicidin D substantially affected the oxygen uptake rate in the absence of DNP-INT, and only slightly in its presence. Such differences pointed to the presence of special oxygen reduction site(s) in photosynthetic electron transport chain `before' cytochrome complex. Oxygen uptake in membrane fragments of Photosystem II (BBY-particles) was low and did not depend on pH. This did not support the participation of Q B in oxygen reduction in DNP-INT-treated thylakoids. Oxygen uptake in thylakoids in the presence of DNP-INT was inhibited by DCMU as well as by catalase in whole pH range. The catalase effect indicated that oxygen uptake was the result of dioxygen reduction by electrons derived from water, and that H2O2 was a final product of this reduction. Photoreduction of Cyt c in the presence of DNP-INT was partly inhibited by superoxide dismutase (SOD), and this pointed to superoxide formation. The latter was confirmed by a rise of the oxygen uptake rate in the presence of ascorbate and by suppression of this rise by SOD. Both tests showed that the detectable superoxide radicals averaged 20-25% of potentially formed superoxide radicals the quantity of which was calculated from the oxygen uptake rate. The obtained data implies that the oxygen reduction takes place in a plastoquinone pool and occurs mainly inside the membrane, where superoxide can be consumed in concomitant reactions. A scheme for oxygen reduction in a plastoquinone pool in thylakoid membranes is proposed.