title: Diminution of stationary enzyme activities at increases of pyruvate kinase concentration in a reconstituted enzyme system.
abstract: In a homogeneous and open enzyme system containing phosphofructokinase, pyruvate kinase, adenylate kinase, and glucose 6-phosphate isomerase the consequences of variations of the enzyme concentrations on the stationary enzyme activities have been investigated. An unexpected behavior was observed upon variation of the maximum activity of pyruvate kinase. Depending on the experimental conditions an increase of the concentration of pyruvate kinase resulted either in a diminution or in a stimulation of the stationary activity of this enzyme. An increase of the maximum activity of phosphofructokinase, however, stimulates both the activities of phosphofructokinase and pyruvate kinase. The experimental results are interpreted in terms of a mathematical model, based on the kinetic properties of the enzymes involved. The correlation between the observed changes of the activities of phosphofructokinase and pyruvate kinase and the appearance of multiple stationary states is discussed.
mesh_terms: D000263:Adenylate Kinase / Q000378:metabolism; D004734:Energy Metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004800:Enzymes, Immobilized / Q000378:metabolism*; D005956:Glucose-6-Phosphate Isomerase / Q000378:metabolism; D007700:Kinetics; D008433:Mathematics; D008954:Models, Biological; D010732:Phosphofructokinase-1 / Q000378:metabolism* / Q000494:pharmacology; D011770:Pyruvate Kinase / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D004800:Enzymes, Immobilized; D010732:Phosphofructokinase-1; D011770:Pyruvate Kinase; D000263:Adenylate Kinase; D005956:Glucose-6-Phosphate Isomerase