| pubmed-article:6216562 | pubmed:abstractText | Kinetic characteristics of glycolytic kinases in cells of the erythrocytic line have been studied in rats. Erythrocyte Hexokinase (HK) shows low Km, while in reticulocytes a high Km enzyme is also found. The low Km HK is inhibited by higher than physiological concentrations of 2,3-bisphosphoglycerate. The ATP inhibition of 6-phosphofructokinase (PFK) from erythrocytes and reticulocytes, and the deinhibitory effect shown by AMP and cyclic-AMP, are lower in situ than in vitro. The sigmoidal fructose-6-phosphate saturation curve for PFK is observed in vitro but not in situ. Under this approach the enzyme shows hyperbolic kinetics, lower response to positive allosteric effectors and a decrease in activity. An antagonistic effect is shown by cyclic-AMP and cyclic-GMP on the in vitro sigmoidal behaviour of PFK. Phosphoglycerate kinase (PGK) is an hyperbolic enzyme, with similar Km values, in erythrocytes, reticulocytes and bone marrow cells. Pyruvate kinase shows sigmoidal kinetics and activation by fructose-1,6-bisphosphate (FBP) in erythrocytes; a non rectangular hyperbolic kinetics with negative cooperativity, lack of response to FBP and inhibition by ATP and L-alanine, was observed in the bone marrow enzyme. | lld:pubmed |
