Kinetic Propertles of the ATP-Dependent Phosphofructoklnase Isoenzymes from Cucumber Seeds

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概要

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• Two isoenzymes of ATP:D-fructose-6-phosphate 1-phosphotransferase (phosphofructokinase) are present in germinating cucumber seeds, one in the plastids and the other in the cytosol. Both isoenzymes were purified and some of their kinetic properties studied. These two isoenzymes differ kinetically, the pH optimum of the cytosolic isoenzyme being 7.2 and that of the plastid isoenzyme being 8.0. Both isoenzymes are activated by phosphate although the concentration required for activation is much lower for the plastid isoenzyme than cytosolic isoenzyme. Phosphate increases the affinity of the isoenzymes for fructose-6-phosphate and also changes the sigmoidal kinetics of the plastid isoenzyme for this substrate to hyperbolic kinetics at pH 7.2. The fructose-6-phosphate saturation kinetics of the cytosolic isoenzyme becomes more sigmoidal with an increase in pH while the opposite is true for the plastid isoenzyme. The cytosolic isoenzyme has a higher affinity for fructose-6-phosphate at pH 7.2 than pH 8.0 while the afiinity of the plastid isoenzyme for fructose-6-phosphate is highest at pH 8.0. Both isoenzymes are inhibited by ATP and the extent of inhibition is pH dependent. The cytosolic isoenzyme is more sensitive to ATP inhibition at pH 8.0 than pH 7.2 while the opposite holds for the plastid isoenzyme. Magnesium alleviates the ATP inhibition of the plastid isoenzyme suggesting that free ATP is the inhibitory form. In contrast the ATP inhibition of the cytosolic isoenzyme apparently appears to be caused by the magnesium-ATP complex.

• 日本植物生理学会の論文

著者

• Botha Frederik

  Department Of Botany And Genetics University Of The Orange Free State

• Small J.

  Department Of Botany University Of The Orange Free State

• Cawood Mareta

  Department of Botany, University of the Orange Free State

• Cawood Mareta

  Department Of Botany University Of The Orange Free State

関連論文

• Effect of Anoxia on the Expression and Molecular Form of the Pyrophosphate Dependent Phosphofructokinase
• Immunological Characterization of the Pyrophosphate Dependent Fructose- 6-Phosphate Phosphotransferase
• Molecular PropertieS Of the ATP:_D-Fructose-6-Phosphate 1-Phosphotransferase Isoenzymes from Cucumis sativus
• Activity of Key Enzymes Involved in Carbohydrate Metabolism in Phaseolus vulgaris Cell Suspension Cultures
• Isolation and Characterization of Pyrophosphate : _D-Fructose-6-phosphate 1-Phosphotransferase from Cucumber Seeds
• Kinetic Propertles of the ATP-Dependent Phosphofructoklnase Isoenzymes from Cucumber Seeds

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