A phosphoglycerate to inorganic phosphate ratio is the major factor in controlling starch levels in chloroplasts via ADP‐glucose pyrophosphorylase regulation

FEBS Letters

Kleczkowski, Leszek A¹ 

[1] Department of Plant Physiology, Umeå University, 901 87 Umeå, Sweden

关键词: Allosteric effector;    Light regulation;    Photosynthesis;    Starch synthesis;   

DOI  :  10.1016/S0014-5793(99)00346-4

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Purified barley leaf ADP-glucose pyrophosphorylase, a key enzyme of the starch synthesis in the chloroplast stroma, was analysed with respect to its possible regulation by factors defining the metabolic/effector status of the chloroplast during light and dark conditions. The enzyme required 3-phosphoglyceric acid for the maximal activity and was inhibited by inorganic phosphate. The optimal pH for the enzyme was at circa 7.0, regardless of the presence or absence of 3-phosphoglyceric acid, whereas the maximal activation by 3-phosphoglyceric acid was observed at pH 8.5 and higher. Changes in the concentration of Mg²⁺ and dithiothreitol had little or no effect on the enzymatic activity of AGPase. It has been directly demonstrated for the first time that a 3-phosphoglyceric acid/inorganic phosphate ratio, a crucial regulatory parameter, could be directly related to a defined activation state of the enzyme, allowing the prediction of a relative AGPase activity under given conditions. The predicted changes in the enzyme activity were directly correlated with earlier reported responses of starch levels to the 3-phosphoglyceric acid/inorganic phosphate ratio in chloroplasts. Consequences of this for the starch biosynthesis are discussed.

【 授权许可】

Unknown