Rate of PRPP Formation . Enzyme Activities . and Intermediate Concentrations in Erythrocytes From Norm Patient

RBCs from patients with hemolytic anemia due to pyruvate kinase (PK) deficiency are characterized by a decreased total adenine and pyridine nucleotide content. Because phosphoribosylpyrophosphate (PRPP) is a precursor of both adenine and pyridine nucleotides, we investigated the ability of intact PK-deficient RBCs to accumulate PRPP. The rate of PRPP formation in normal RBCs (n = 1 1 ) was 2.89 ± 0.80 nmol/min . ml RBCs. In contrast, the rate of PRPP formation in PK-deflcient RBCs (n 4) was markedly impaired at 1 .03 ± 0.39 nmol/min . mL RBCs. Impaired PRPP formation in these cells was not due to the higher proportion of reticulocytes. To study the mechanism of impaired PRPP formation, PK deficiency was simulated by