1987 Fiscal Year Final Research Report Summary
Regulation in glycolysis in plants - Role of fructose-2,6-bisphosphate and pyrophosphate-dependent phosphofructokinase
| Project/Area Number |
60480010
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
植物生理学
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| Research Institution | Ochanomizu University |
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Principal Investigator |
ASHIHARA Hiroshi Faculty of Science, Ochanomizu University, Associate Professor, 理学部, 助教授 (00017211)
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| Project Period (FY) |
1985 – 1987
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| Keywords | Glycolysis / Metabolic Regulation / Plant Cell Culture / Phosphofructokinase / Fructose-2,6-bisphosphate / ピロリン酸 |
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| Research Abstract |
In addition to ATP-dependent phosphofructokinase (ATP-PFK), higher plants possess the enzyme pyrophosphate:fructose 6-phosphate 1-phosphotransferase (PPi-PFK). In this study, we first determined some kinetic values of ATP- PFK and PPi-PFK purified from suspension-cultured cells of Catharanthus roseus. The results indicate that the activity of ATP-PFK is controlled by adenylate energy charge and that of PPi-PFK is regulated by fructose- 2,6-bisphosphate (F2,6BP) and inorganic phosphate (Pi). The maximum catalytic activity of PPi-PFK was approximately three fold greater than that of ATP-PFK. Estimated intracellular concentration of F2,6BP and PPi were 2 uM and 1 mM, respectively. These results suggest that PPi-PFK is functional in the cells in vivo.
Profiles of glycolytic activity in batch suspension cultures of Catharanthus roseus were determined for the cells at different stages of culture and the following results were obtained. (a) Sucrose in the culture medium was almost completely hydrolyzed to glucose and fructose within 3 days of initiation of a standard culture. (b) Most of the activities of glycolytic enzymes were located in the cytosol, but some hexose-phosphorylating activity was found in the mitochondrial fraction. (c) From a comparison of the maximum catalytic activities of all the enzymes involved in glycolysis, it appears that hexokinase, fructokinase, ATP-PFK, and pyruvate kinase have activities which are low in relation to the activities of other glycolytic enzymes. (d) F2,6BP activated PPi-PFK, but this compound had no significant effect on the activities of any of the other glycolytic enzymes. The present results indicated that the activity of PPi-PFK in the cells may be regulated by the cytosolic concentration of PPi and F2,6BP. However, in the presence of sufficient amounts of these compound, the step catalyzed by hexokinase, fructokinase and pyruvate kinase are most probably the rate-limiting steps in the flux of glycolysis in the cells in vivo.
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