The dependence of oxygen evolution in PS Ⅱ from spinach Spinacia oleracea L. on the content of exogenous anionic phosphatidylglycerol (PG) at pH 6.0 was investigated through reconstitution experiment. It was found that there was a steady increase in oxygen evolution. With increasing PG/PS Ⅱ ratio up to a maximum at concentrations ranging from 10-22 mg PG/mg chlorophyll (Chl). Then, further addition of PG resulted in the inhibitions of oxygen evolution. With a PG/PS Ⅱ ratio of 40 mg PG/mg Chl, the oxygen-evolving activity of PS Ⅱ decreased to 40% of the untreated PS Ⅱ. It is suggested that a stimulation of oxygen evolution at a low PG/Chl ratio was resulted from the structural optimization of PS Ⅱ by PG while an inhibitory effect on oxygen evolution at higher values of this ratio was ascribed to the structural changes of extrinsic proteins of PS Ⅱ owing to osmotic pressure.
磷脂酰甘油对光系统II放氧活性的影响
阳振乐 李良壁 许亦农 匡廷云*
（中国科学院植物研究所光合作用研究中心， 北京100093）
摘要：通过重组试验表明 ,磷脂酰甘油 (PG)对菠菜 (Spinaciaoleracea L .)光系统Ⅱ (PSⅡ )的放氧活性产生显著影响 ,具有明显的浓度效应。随PG浓度的增加 ,PSⅡ的放氧能力逐渐增强 ,到 10mgPG /mgChl时PSⅡ活性达到最大。此后在 10～ 2 2mgPG/mgChl浓度范围内 ,PSⅡ放氧活性变化不大。而当PG浓度继续增大时 ,PSⅡ放氧活性迅速降低 ,40mgPG/mgChl时的PSⅡ活性已降至未处理PSⅡ的 40 %。放氧活性的增强是由于PG维持了色素蛋白的适宜结构 ,而放氧活性的降低可归之于渗透效应而致的外周蛋白结构的改变。
关键词： 光系统II；磷酯酰甘油；放氧活性；浓度效应
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