Lendzian K, Bassham J A
Biochim Biophys Acta. 1976 Jun 8;430(3):478-89. doi: 10.1016/0005-2728(76)90024-4.
Levels of reduced and oxidized triphosphopyridine nucleotides have been determined in reconstituted spinach chloroplasts and compared with levels in whole isolated chloroplasts during photosynthesis and darkness. The ratio of NADPH/NADP+ reaches values slightly above 1.0 at the beginning of photosynthesis, less than half the ratio attained with whole chloroplasts. Nonetheless these lower ratios are sufficient to maintain high rates of photosynthetic carbon dioxide fixation and reduction, which are comparable in the reconstituted chloroplasts to the rates found with whole chloroplasts. As with whole chloroplasts there is a decline in the ration of NADPH/NADP+ as a function of time of photosynthesis. The effect of addition of bicarbonate (6 mM) in causing a transient drop in the ratio of NADPH/NADP/ is described and discussed in terms of the reversibility of the reduction of 3-phosphoglycerate to triose phosphate. The ratio NADPH/NADP+ can be improved by the addition of more lamellae either before or during the course of photosynthesis, and this improvement in ratio is accompanied by an improved rate of CO2 fixation or a more sustained rate of CO2 fixation with time of photosynthesis. The importance of NADPH/NADP+ ratio not only to the reduction of 3-phosphoglycerate to triose phosphate but also to the activation of the ribulose-1,5-diphosphate carboxylasemediated step is discussed.
已测定了重组菠菜叶绿体中还原型和氧化型三磷酸吡啶核苷酸的水平，并与完整分离叶绿体在光合作用和黑暗条件下的水平进行了比较。在光合作用开始时，NADPH/NADP⁺的比值略高于1.0，不到完整叶绿体所达到比值的一半。尽管如此，这些较低的比值足以维持较高的光合二氧化碳固定和还原速率，重组叶绿体中的这些速率与完整叶绿体中的速率相当。与完整叶绿体一样，NADPH/NADP⁺的比值会随着光合作用时间的延长而下降。描述并讨论了添加碳酸氢盐（6 mM）导致NADPH/NADP⁺比值瞬间下降的影响，这与3-磷酸甘油酸还原为磷酸丙糖的可逆性有关。在光合作用之前或过程中添加更多类囊体可以提高NADPH/NADP⁺的比值，并且这种比值的提高伴随着二氧化碳固定速率的提高或随着光合作用时间的延长二氧化碳固定速率更持久。讨论了NADPH/NADP⁺比值不仅对3-磷酸甘油酸还原为磷酸丙糖的重要性，而且对1,5-二磷酸核酮糖羧化酶介导步骤的激活的重要性。
