Characterization of Glucose-6-Phosphate Incorporation into Starch by Isolated Intact Cauliflower-Bud Plastids
Characterization of Glucose-6-Phosphate Incorporation into Starch by Isolated Intact Cauliflower-Bud Plastids
复制标题
分离的完整花椰菜芽质体对 6-磷酸葡萄糖掺入淀粉的表征
作者：
H.;E. Neuhaus;Cudrun Henrichs;R. Scheibe
根据E.P.E.P.E.P.E.D.net和R. Douce描述的方法从花椰菜（Brassica oleracea var Prince de Bretagne）芽中分离出完整的质体。Douce [1985] Plant Physiol 79：458-）467）。这些质体与各种14 C标记的化合物的孵育显示，葡萄糖-6-磷酸可以作为淀粉合成的前体。然而，只有当3-磷酸甘油酸和ATP同时存在时，才能观察到显著的速率（掺入120 nmol葡萄糖mg-1蛋白h-1）。在离体质体中淀粉的合成强烈依赖于细胞器的完整性。通过[14 C]ATP的摄取实验证明了高亲和力ATP/ADP转运子的存在，其ATP的Km为12 [mu]M。ADP抑制ATP摄取和效应刺激的淀粉合成。果糖-6-磷酸或2-脱氧葡萄糖-6-磷酸对葡萄糖-6-磷酸依赖的淀粉合成没有显著影响，但磷酸丙糖和无机磷酸盐强烈抑制。淀粉合成也被抑制4，4 [总理]-二异硫代-氰基芪-2，2 [总理]-二磺酸盐，这是已知的是一种有效的抑制剂的叶绿体磷酸转运。这里提供的数据支持这样的观点，即在异养组织中淀粉的生物合成是由细胞溶质3-磷酸甘油酸和ATP的水平增加时，葡萄糖-6-磷酸是可用的。
Intact plastids from cauliflower (Brassica oleracea var Prince de Bretagne) buds were isolated according to the method described by Journet and Douce (E.P. Journet and R. Douce [1985] Plant Physiol 79: 458–)467). Incubation of these plastids with various 14C-labeled compounds revealed that glucose-6-phosphate can act as a precursor for starch synthesis. However, significant rates (incorporation of 120 nmol glucose mg-1 protein h-1) could only be observed when both 3-phosphoglyceric acid and ATP were present as well. Starch synthesis in isolated plastids was strongly dependent upon the intactness of the organelle. The presence of a high-affinity ATP/ADP translocator with a Km for ATP of 12 [mu]M was demonstrated by uptake experiments with [14C]ATP. ADP inhibited both ATP uptake and effector-stimulated starch synthesis. Effector-stimulated glucose-6-phosphate-dependent starch synthesis was not significantly influenced by fructose-6-phosphate or 2-deoxyglucose-6-phosphate but was strongly inhibited by triose phosphate and inorganic phosphate. Starch synthesis was also inhibited by 4,4[prime]-diisothio-cyanostilbene-2,2[prime]-disulfonate, which is known to be a potent inhibitor of the chloroplast phosphate translocator. The data presented here support the view that starch biosynthesis in heterotrophic tissues is powered by increasing levels of cytosolic 3-phosphoglyceric acid and ATP when glucose-6-phosphate is available.