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):109-13. doi: 10.1104/pp.63.1.109.
The rate of ADP-glucose formation from [(14)C]glucose 6-phosphate and ATP by the soluble fraction of lysed chloroplasts is studied as a function of the levels of metabolites (3-phosphoglycerate, orthophosphate, hexose monophosphate, and ATP) as determined in whole chloroplasts of Spinacia oleracea in light and dark.A change in 3-phosphoglycerate concentration (from 4 to 1.4 millimolar, as in whole chloroplasts during light-dark transition) decreases the rate of ADP-glucose formation 6- to 7-fold. An increase in hexose monophosphate concentration from 2 to 6 millimolar, which occurs at the same time in whole chloroplasts, stimulates ADP-glucose formation only slightly.At constant levels of orthophosphate (4 millimolar) and 3-phosphoglycerate (4 millimolar), a change in ATP concentration from 0.2 to 1 millimolar causes an immediate 4- to 5-fold increase in the rate of ADP-glucose formation. Another significant stimulation of ADP-glucose formation (about 4- to 6-fold) is obtained after addition of dithiothreitol at high concentrations (50 millimolar). A simultaneous increase in the concentrations of 3-phosphoglycerate, ATP, and dithiothreitol, with orthophosphate and Mg(2+) being constant at 4 and 5 millimolar, respectively, causes a 130-fold increase in the rate of ADP-glucose formation (from 0.042 to 5.49 microgram atoms carbon per milligram chlorophyll per hour).The role of these and other factors is discussed with respect to light-dark regulation of starch formation in intact chloroplasts.
研究了裂解叶绿体的可溶部分由[¹⁴C]葡萄糖6-磷酸和ATP形成ADP-葡萄糖的速率，该速率是菠菜完整叶绿体在光照和黑暗条件下所测定的代谢物（3-磷酸甘油酸、正磷酸盐、单磷酸己糖和ATP）水平的函数。3-磷酸甘油酸浓度的变化（从4毫摩尔降至1.4毫摩尔，如在光照-黑暗转换期间完整叶绿体中的变化）使ADP-葡萄糖形成速率降低6至7倍。单磷酸己糖浓度从2毫摩尔增加到6毫摩尔（这在完整叶绿体中同时发生），仅轻微刺激ADP-葡萄糖的形成。在正磷酸盐（4毫摩尔）和3-磷酸甘油酸（4毫摩尔）水平恒定的情况下，ATP浓度从0.2毫摩尔变为1毫摩尔会立即使ADP-葡萄糖形成速率增加4至5倍。加入高浓度（50毫摩尔）的二硫苏糖醇后，ADP-葡萄糖的形成受到另一次显著刺激（约4至6倍）。在正磷酸盐和Mg²⁺分别恒定在4毫摩尔和5毫摩尔的情况下，同时增加3-磷酸甘油酸、ATP和二硫苏糖醇的浓度，会使ADP-葡萄糖形成速率增加130倍（从每毫克叶绿素每小时0.042微克原子碳增加到5.49微克原子碳）。讨论了这些及其他因素在完整叶绿体淀粉形成的光-暗调节方面的作用。
