Neumann J, Levine R P
The Biological Laboratories, Harvard University, Cambridge, Massachusetts 02138.
Plant Physiol. 1971 May;47(5):700-4. doi: 10.1104/pp.47.5.700.
Illumination of a suspension of Chlamydomonas reinhardi causes an increase in the pH of the medium which is reversed in the dark. This pH change is a manifestation of CO(2) uptake in the light and its evolution in the dark. Simultaneous measurements of pH changes and oxygen evolution reveal that the photosynthetic coefficient approaches one.Intact cells of F-60, a mutant strain of C. reinhardi that lacks an active phosphoribulokinase, do not exhibit the light-dependent pH increase or oxygen evolution. However, chloroplast fragments prepared from the cells of the mutant strain exhibit a normal "proton pump" activity.The light-dependent pH increase shown by intact cells can be inhibited by KCN, by uncouplers of photosynthetic phosphorylation, and by Dio-9. It is markedly increased upon the addition of potassium bicarbonate, and all inhibitors tested inhibit the pH increase in both the presence and absence of potassium bicarbonate.The results of the present work negate the conclusion of other workers that the light-dependent pH changes in intact cells of C. reinhardi (and probably in other algae as well) are due to the operation of the "proton pump."
莱茵衣藻悬浮液受光照会导致培养基pH值升高，黑暗中则会逆转。这种pH值变化是光照下二氧化碳吸收以及黑暗中二氧化碳释放的一种表现。同时测量pH值变化和氧气释放表明，光合系数接近1。F - 60是莱茵衣藻的一个突变株，缺乏活性磷酸核酮糖激酶，其完整细胞不会表现出光依赖的pH值升高或氧气释放。然而，从该突变株细胞制备的叶绿体片段表现出正常的“质子泵”活性。完整细胞所显示的光依赖pH值升高可被氰化钾、光合磷酸化解偶联剂和Dio - 9抑制。加入碳酸氢钾后，pH值显著升高，并且所有测试的抑制剂在有和没有碳酸氢钾的情况下都能抑制pH值升高。本研究结果否定了其他研究者的结论，即莱茵衣藻（可能其他藻类也是如此）完整细胞中光依赖的pH值变化是由于“质子泵”的作用。
