[Significance of kinetic abnormalities of erythrocyte pyruvate kinase in congenital deficiencies].

Kinetic studies of semi-purified pyruvate kinase were performed from the erythrocytes of 22 subjects with congenital non-spherocytic anemia with pyruvate kinase deficiency and 25 heterozygous relatives. The study of enzyme affinity for PEP with and without ligands fructose-diphosphate (FDP) and ATP allowed to separate three groups of patients: --in eight patients and their eleven heterozygous relatives, the PK kinetic characteristics were similar to those of controls. Allosteric properties of the enzyme were normal; --in three patients, PK was in an activated form, non sensitive to FDP activation and to ATP inhibition in the experimental conditions. The deficient enzyme seemed to be present in the "R" form; --in eleven patients affinity for PEP was decreased; the enzyme was in each case activated by FDP; however very high FDP concentrations did not allow to obtain a complete activation and an n Hill of 1. ATP inhibition was more important than in controls. Similar results were obtained in some heterozygous relatives. The pyruvate kineases of these patients seemed to be fixed in "T" form. Whatever may be the molecular abnormalities responsible for the PK deficiency, they seem to lead in many cases to a change in the enzyme allosteric properties.