Alterations in erythrocyte enzymes in cancer.

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.