Uptake and phosphorylation of glucose and fructose in Daucus carota cell suspensions are differently related
| Autor: | L.H.W. van der Plas, Dick Vreugdenhil, J. Krook |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2000 |
| Předmět: |
(soluble) fructokinase
Sucrose Physiology Fructose 1 6-bisphosphatase Plant Science Fructokinase chemistry.chemical_compound Hexose Genetics Glycolysis Laboratorium voor Plantenfysiologie (membrane-associated) hexokinase biology Glucokinase Respiration Daucus carota (cell suspensions) Fructose chemistry Biochemistry Sugar uptake Fructolysis biology.protein Phosphoglucomutase EPS Laboratory of Plant Physiology |
| Zdroj: | Plant Physiology and Biochemistry, 38, 603-612 Plant Physiology and Biochemistry 38 (2000) |
| ISSN: | 0981-9428 |
| DOI: | 10.1016/s0981-9428(00)00776-2 |
| Popis: | Cell suspensions of Daucus carota L. were grown in batch culture on 50 mM sucrose, 100 mM glucose or 100 mM fructose. Sucrose was rapidly converted extra-cellularly into equimolar amounts of glucose and fructose, and glucose was then taken up preferentially. This impaired uptake of fructose could partially be explained by the eight-fold lower affinity of the hexose carrier in the plasmamembrane for fructose compared to glucose. However, cells grown on fructose as the sole carbon source showed a shorter lag phase and showed more biomass production compared to glucose-grown cells, indicating that conversion of glucose and fructose were also differently regulated. Ninety-five % of the glucose phosphorylating activity was membrane-associated and most probably confined to mitochondria; therefore, it might be present in a respiratory ‘compartment’ making glucose a better substrate for respiration than fructose. The soluble fraction contained the majority of the fructokinase activity. This activity was hypothesized to be more or less randomly distributed through the cytosol; in this soluble ‘compartment’ a pool of fructose-6-phosphate is formed. Concomitantly, via glucose-6-phosphate (G-6-P) and glucose-1-phosphate (G-1-P), it is converted into UDPG-glucose, resulting in structural cell components. The observed transient obstruction of the conversion of G-1-P into UDP-glucose in fructose-grown cells, leading to G-1-P accumulation, might be a result of both an altered equilibrium maintained by phosphoglucomutase, interconverting G-6-P and G-1-P and low levels of nucleotide triphosphates. Low nucleotide triphosphate production, connected with a low initial respiration rate, might be caused by the ten-fold lower affinity of the membrane-associated phosphorylating enzymes for fructose compared to glucose. Our results were taken to indicate that two separate pools of glycolytic intermediates exist in D. carota cells: one distributed throughout the cytosol and one surrounding the mitochondria. |
| Databáze: | OpenAIRE |
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