Biomedical subjects
Publications and source records attributed to D Kwiatkowska.
Phosphofructokinase isolated from human erythrocytes incubated with cortisol showed alterations in regulatory properties. The enzyme was more sensitive to the inhibition by ATP and citrate. This effect was abolished by alanine. Similar changes in phosphofructokinase properties were found after incubation with aldosterone and corticosterone.
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After incubation of rabbit red blood cells with 10 micrograms/ml of cortisol, a decrease of the activity of glucose-6-phosphate dehydrogenase, phosphofructokinase and acid phosphatase was observed. Glucose-6-phosphate dehydrogenase and phosphofructokinase were isolated from hemolysate and investigated. No changes in the affinity of both enzymes towards substrates and coenzymes were found. Cortisol modified allosteric properties of phosphofructokinase. Differences were seen between the erythrocyte and reticulocyte enzyme. In the erythrocyte enzyme the inhibitory effect of ATP and citrate was enhanced and the activatory effect of AMP was abolished after incubation with cortisol. Cortisol showed no effect on the inhibition of reticulocyte phosphofructokinase by ATP or activation by AMP, and protected the enzyme toward inhibition by citrate.
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An increase in lactate production, and in activities of phosphohexoisomerase, phosphofructokinase and pyruvate kinase was found in erythrocytes of patients with advanced cancer disease. Phosphofructokinase isolated from patients' erythrocytes showed enhanced affinity for substrate and coenzyme, diminished thermal stability and changed dependence of the activity on pH. Allosteric properties of the enzyme were modified. A decrease in glucose-6-phosphate dehydrogenase activity was observed in hemolysate. The partially purified enzyme showed decreased affinity for glucose-6-phosphate, and markedly reduced stability at 45 degrees C and in the acid and alkaline pH range. Changes in kinetic and molecular properties of the two key enzymes of glucose metabolism may contribute to hemolysis observed in many cancer patients. Incubation in vitro of normal human erythrocytes with blood sera of patients resulted in increasing of phosphofructokinase, and decreasing of glucose-6-phosphate dehydrogenase activity, indicating that an acquired enzymopathy may be present in cancer.
Bilipolinum (Adipiodon), iodine contrast medium used in cholangiography, showed an inhibitory effect on the activity of human erythrocyte phosphohexoseisomerase, phosphofructokinase, aldolase and glucose-6-phosphate dehydrogenase. The addition of glucose metabolites (glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-bis-phosphate, pyruvate and lactate) abolished the inhibitory effect of Bilipolinum. In the presence of Bilipolinum purified erythrocyte phosphofructokinase showed a decreased affinity towards substrate, modified allosteric properties and reduced stability at pH below 7.5. Purified erythrocyte glucose-6-phosphate dehydrogenase was also affected by Bilipolinum and its affinity for NADP was decreased. Testing of erythrocyte enzymes in the evaluation of toxicity of iodine contrast media is discussed.
Erythrocyte glucose-6-phosphate dehydrogenase from patients with acute viral hepatitis has been purified and characterized. The enzyme showed decreased activity (relative to protein), reduced affinity for glucose 6-phosphate and was inactivated at 45 degrees C or at low pH values. The activity and properties of normal erythrocyte enzyme, incubated in vitro with blood plasma of patients, showed a similar pattern of modifications. Incubation with bilirubin affected the enzyme stability, but not its activity or affinity for substrate.
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