GLUCONEOGENESIS IN CASTOR BEAN ENDOSPERM .1. CHANGES IN GLYCOLYTIC INTERMEDIATES
GLUCONEOGENESIS IN CASTOR BEAN ENDOSPERM .1. CHANGES IN GLYCOLYTIC INTERMEDIATES
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DOI：
10.1104/pp.47.1.48
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发表时间：
1971-01-01
期刊：
影响因子：
7.4
通讯作者：
BEEVERS, H
中科院分区：
文献类型：
--
作者：
KOBR, MJ;BEEVERS, H
蓖麻种子萌发过程中Embden-Meyerhof-Parnas途径的调控点（Ricinus communis）胚乳以两种方式寻找：（a）通过在萌发期间间隔测量各种糖酵解中间体的量;（B）通过确定在缺氧期间出现的交叉点，在果糖1的水平发现底物和产物之间的热力学平衡的显著偏离，6-二磷酸酶和磷酸果糖激酶。一个明确的转变，这一比例是观察到在发病的积极的异生。磷酸烯醇丙酮酸和3-磷酸甘油酸的浓度同时增加。另一个偏离预期的平衡也观察到在丙酮酸激酶的水平上，对5日龄胚乳施加缺氧揭示了两个交叉点，在同一酶的水平。因此，它们调节糖酵解流量，但最大糖酵解流量仅为促糖酵解流量的1/10。为了解释这种高的糖酵解效率，假设糖酵解和糖酵解发生在不同的细胞内区域。在缺氧的早期阶段观察到腺苷酸之间的平衡的一致偏离支持的概念，即糖酵解和代谢中间体的池确实是分隔的，这两个过程是独立的调节。
The control points of the Embden-Meyerhof-Parnas pathway in germinating castor bean (Ricinus communis) endosperms are sought in two ways: (a) by measuring the amounts of various glycolytic intermediates at intervals during the germination; (b) by determining the crossover points appearing during anoxia.A significant departure from thermodynamic equilibrium between substrates and products is found at the level of fructose 1,6-diphosphatase and phosphofructokinase. A definite shift of this ratio is observed at the onset of active gluconeogenesis. The concentrations of phosphoenolpyruvate and 3-phosphoglyceric acid increase at the same time. Another departure from the expected equilibrium is also observed at the level of the pyruvate kinase.The imposition of anoxia on 5-day-old endosperms reveals two crossover points, at the level of the same enzymes. It is therefore concluded that they regulate the glycolytic flow.The maximal glycolytic flow, however, is only 1/10 of the gluconeogenic one. To account for this high gluconeogenic efficiency, it is postulated that gluconeogenesis and glycolysis occur in separate intracellular regions. The consistent departure from equilibrium between adenylates observed during the early stages of anoxia supports the concepts that the pools of glycolytic and gluconeogenic intermediates are indeed compartmented and that the two processes are independently regulated.