CSIRO, Division of Horticultural Research, GPO Box 350, 5001, Adelaide, Australia.
Photosynth Res. 1987 Jan;14(3):211-27. doi: 10.1007/BF00032706.
Intact chloroplasts isolated from spinach were illuminated in the absence of inorganic phosphate (Pi) or with optimum concentrations of Pi added to the reaction medium. In the absence of Pi photosynthesis declined after the first 1-2 min and was less than 10% of the maximum rate after 5 min. Export from the chloroplast was inhibited, with up to 60% of the (14)C fixed being retained in the chloroplast, compared to less than 20% in the presence of Pi. Despite the decreased export, chloroplasts depleted of Pi had lower levels of triose phosphate while the percentage of total phosphate in 3-phosphoglycerate was increased. Chloroplast ATP declined during Pi depletion and reached dark levels after 3-4 min in the light without added Pi. At this point, stromal Pi concentration was 0.2 mM, which would be limiting to ATP synthesis. Addition of Pi resulted in a rapid burst of oxygen evolution which was not initially accompanied by net CO2 fixation. There was a large decrease in 3-phosphoglycerate and hexose plus pentose monophosphates in the chloroplast stroma and a lesser decrease in fructose-1,6-bisphosphate. Stromal levels of triose phosphate, ribulose-1,5-bisphosphate and ATP increased after resupply of Pi. There was an increased export of (14)-labelled compounds into the medium, mostly as triose phosphate. Light activation of both fructose-1,6-bisphosphatase and ribulose-1,5-bisphosphate carboxylase was decreased in the absence of Pi but increased following Pi addition.It is concluded that limitation of Pi supply to isolated chloroplasts reduced stromal Pi to the point where it limits ATP synthesis. The resulting decrease in ATP inhibits reduction of 3-phosphoglycerate to triose phosphate via mass action effects on 3-phosphoglycerate kinase. The lack of Pi in the medium also inhibits export of triose phosphate from the chloroplast via the phosphate transporter. Other sites of inhibition of photosynthesis during Pi limitation may be located in the regeneratige phase of the reductive pentose phosphate pathway.
从菠菜中分离出来的完整叶绿体在缺乏无机磷 (Pi) 或在反应介质中添加最佳浓度 Pi 的情况下进行光照。在没有 Pi 的情况下，光合作用在最初的 1-2 分钟后下降，并且在 5 分钟后不到最大速率的 10%。叶绿体的输出受到抑制，与有 Pi 时相比，多达 60%的（14）C 固定物保留在叶绿体中，不到 20%。尽管出口减少，但 Pi 耗尽的叶绿体中三磷酸甘油醛的水平较低，而 3-磷酸甘油酸中的总磷酸盐百分比增加。在 Pi 耗尽期间，叶绿体 ATP 下降，在没有添加 Pi 的情况下，在光下 3-4 分钟后达到黑暗水平。此时，基质 Pi 浓度为 0.2 mM，这将限制 ATP 合成。添加 Pi 会导致氧气释放的快速爆发，最初并不伴随着净 CO2 固定。叶绿体基质中 3-磷酸甘油酸和己糖加戊糖一磷酸的含量大幅下降，果糖-1,6-二磷酸的含量略有下降。在补充 Pi 后，叶绿体基质中三磷酸甘油醛、核酮糖-1,5-二磷酸和 ATP 的水平增加。标记化合物的大量出口到培养基中，主要是三磷酸甘油醛。在没有 Pi 的情况下，果糖-1,6-双磷酸酶和核酮糖-1,5-二磷酸羧化酶的光激活减少，但在添加 Pi 后增加。结论是，将 Pi 供应限制在分离的叶绿体中，将基质 Pi 降低到限制 ATP 合成的程度。由此产生的 ATP 减少通过对 3-磷酸甘油酸激酶的质量作用效应抑制 3-磷酸甘油酸还原为三磷酸甘油醛。培养基中缺乏 Pi 也会通过磷酸盐转运体抑制三磷酸甘油醛从叶绿体中的输出。在 Pi 限制期间光合作用的其他抑制部位可能位于还原戊糖磷酸途径的再生阶段。
