Portis A R
United States Department of Agriculture, Agricultural Research Service, University of Illinois, Urbana, Illinois 61801.
Plant Physiol. 1983 Apr;71(4):936-43. doi: 10.1104/pp.71.4.936.
The role of the phosphate translocator and the importance of the extrachloroplastic concentrations of phosphate, 3-phosphoglycerate, and dihydroxyacetone phosphate in steady-state photosynthesis is examined with a kinetic model. The steady-state stromal concentrations of these compounds are calculated as a function of the rate of the various partial reactions of photosynthesis, at various external concentrations which span those likely to occur in vivo. It is shown how the net transport requirements of the various reactions necessitate different adjustments in the stromal concentrations of these compounds, away from the equilibrium values expected in the absence of metabolism. Under most circumstances, the high exchange capacity of the phosphate translocator relative to the transport requirements of CO(2) fixation limits the extent of these displacements, but conditions when the phosphate translocator is limiting photosynthesis are observed and discussed. The model provides a basis for a more quantitative understanding of the role of the phosphate translocator and the external concentrations of phosphate, 3-phosphoglycerate, and dihydroxyacetone phosphate in photosynthesis.
利用动力学模型研究了磷酸转运体的作用以及叶绿体外磷酸、3-磷酸甘油酸和磷酸二羟丙酮浓度在稳态光合作用中的重要性。这些化合物的稳态基质浓度是根据光合作用各种部分反应的速率计算得出的，计算时考虑了一系列不同的外部浓度，这些浓度涵盖了体内可能出现的浓度范围。研究表明，各种反应的净运输需求如何使得这些化合物的基质浓度需要进行不同的调整，从而偏离了在无代谢情况下预期的平衡值。在大多数情况下，相对于二氧化碳固定的运输需求，磷酸转运体的高交换能力限制了这些位移的程度，但也观察并讨论了磷酸转运体限制光合作用的情况。该模型为更定量地理解磷酸转运体以及磷酸、3-磷酸甘油酸和磷酸二羟丙酮的外部浓度在光合作用中的作用提供了基础。
