title: Fructose 2,6-bisphosphate metabolism in Ehrlich ascites tumour cells.
abstract: Cancer cell energy metabolism is characterized by a high glycolytic rate, which is maintained under aerobic conditions. In Ehrlich ascites tumour cells, the concentration of fructose 2,6-bisphosphate (Fru-2,6-P2), the powerful activator of 6-phosphofructo-1-kinase, is tenfold increased. The bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2), synthesizing and degrading Fru-2,6-P2, was characterized. The molecular mass is 120 kDa. The dependence of PFK-2 activity on the substrate concentrations is hyperbolic (Km for Fru-6-P = 0.09 mM; Km for ATP = 0.7 mM), while the dependence of the FBPase-2 activity on the concentrations of Fru-2,6-P2 is sigmoidal (K0.5 for Fru-2,6-P2 = 4 microM). The PFK-2/FBPase-2 activity ratio is 1. PFK-2 activity is inhibited by citrate (I0.5 = 0.17 mM) and phosphoenolpyruvate (I0.5 = 0.08 mM) but only weakly by glycerol 3-phosphate (I0.5 = 1.57 mM). In contrast to the liver enzyme, the activity of tumour PFK-2/FBPase-2 is not influenced by the action of cAMP-dependent protein kinase. The kinetic properties as well as ion-exchange chromatography pattern differ from their normal counterparts in liver and muscle. The properties are likely to contribute to the maintenance of the high glycolytic rate in these tumour cells.
mesh_terms: D000469:Alkaline Phosphatase / Q000494:pharmacology; D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D002951:Citrates / Q000494:pharmacology; D019343:Citric Acid; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004800:Enzymes, Immobilized / Q000494:pharmacology; D005635:Fructosediphosphates / Q000378:metabolism*; D005994:Glycerophosphates / Q000494:pharmacology; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D025481:Phosphofructokinase-2; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000201:enzymology
chemical_list: D002951:Citrates; D004791:Enzyme Inhibitors; D004800:Enzymes, Immobilized; D005635:Fructosediphosphates; D005994:Glycerophosphates; D007527:Isoenzymes; D019343:Citric Acid; C027652:fructose 2,6-diphosphate; C029620:alpha-glycerophosphoric acid; D017853:Phosphotransferases (Alcohol Group Acceptor); D025481:Phosphofructokinase-2; D000469:Alkaline Phosphatase; D010744:Phosphoric Monoester Hydrolases