Kaiser W M, Bassham J A
Laboratory of Chemical Biodynamics, Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720.
Plant Physiol. 1979 Jan;63(1):105-8. doi: 10.1104/pp.63.1.105.
In Spinacia oleracea the kinetics of CO(2) fixation, of starch formation, and of changes in the levels of metabolites in chloroplasts and the surrounding medium has been investigated during light-dark and dark-light transitions with isolated intact chloroplasts.The internal level of orthophosphate stays constant throughout a light-dark-light cycle. The concentration of 3-phosphoglycerate in the chloroplasts is about 4 millimolar in the light and decreases in the dark within 3 minutes to about 1.6 millimolar. The level of the hexose monophosphates shows a reverse trend, increasing from about 2.2 millimolar in the light to 6 millimolar in darkness. In the subsequent light period both compounds reach their original levels within 2 minutes. The chloroplastic concentrations of dihydroxyacetone phosphate, of the pentose monophosphates, and of the hexose- and heptose bisphosphates remain constant at about 0.4 millimolar throughout the light-dark-light cycle.In the medium, the concentration of 3-phosphoglycerate increases and dihydroxyacetone phosphate decreases in the dark phase: this is due to an exchange of internal 3-phosphoglycerate for external dihydroxyacetone phosphate. Part of the reimported dihydroxyacetone phosphate is converted into hexose monophosphates via aldolase and fructose bisphosphatase during the first minutes of darkness. Due to the observed exchange transport reactions, the large difference between the transenvelope concentration gradients of 3-phosphoglycerate, dihydroxyacetone phosphate, and orthophosphate which exist in the light, is completely abolished after 2 to 3 minutes in the dark.The kinetics and the magnitudes of the changes of metabolite concentrations during the light-dark-light cycle are compared to the kinetics of starch formation, and their relevance for a possible light-dark regulation of starch synthesis is discussed.
在菠菜中，利用分离的完整叶绿体，研究了在明暗交替和暗明交替过程中，叶绿体及周围介质中二氧化碳固定、淀粉形成以及代谢物水平变化的动力学。在整个明暗光周期中，叶绿体内部的正磷酸盐水平保持恒定。叶绿体中3-磷酸甘油酸的浓度在光照下约为4毫摩尔，在黑暗中3分钟内降至约1.6毫摩尔。己糖单磷酸的水平呈现相反趋势，从光照下的约2.2毫摩尔增加到黑暗中的6毫摩尔。在随后的光照期，这两种化合物在2分钟内都恢复到原来的水平。在整个明暗光周期中，磷酸二羟丙酮、戊糖单磷酸以及己糖和庚糖双磷酸的叶绿体浓度保持在约0.4毫摩尔不变。在培养基中，3-磷酸甘油酸的浓度在黑暗阶段增加，磷酸二羟丙酮减少：这是由于内部3-磷酸甘油酸与外部磷酸二羟丙酮的交换。在黑暗的最初几分钟内，重新导入的部分磷酸二羟丙酮通过醛缩酶和果糖双磷酸酶转化为己糖单磷酸。由于观察到的交换转运反应，光照下存在的3-磷酸甘油酸、磷酸二羟丙酮和正磷酸盐跨包膜浓度梯度之间的巨大差异，在黑暗中2至3分钟后完全消除。将明暗光周期中代谢物浓度变化的动力学和幅度与淀粉形成的动力学进行了比较，并讨论了它们与淀粉合成可能的明暗调节的相关性。
