磷脂酰甘油对光系统Ⅱ放氧活性的影响

Effect of Phosphatidylglycerol on Oxygen Evolution in Photosystem II

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.