Expression and characterization of glucose-6-phosphate dehydrogenase of Plasmodium falciparum.

Glucose-6-phosphate dehydrogenase (G6PD) from Plasmodium falciparum has been detected previously in cultures of parasites grown in G6PD-deficient red blood cells. Using polyacrylamide gel electrophoresis, a semi-quantitative assay has been developed to compare the level of the parasite enzyme activity in G6PD normal and in G6PD-deficient host cells. The results do not support the previous contention that the host cell G6PD-deficiency necessarily affects the level of expression of the parasite enzyme. The plasmodial enzyme was partially purified from extracts of parasites prepared by digitonin lysis of infected red blood cells, and its distinctive biochemical properties are described. P. falciparum G6PD has a KmG6P of 27 microM, a KmNADP of 4.5 microM, and KiNADPH of 4.5 microM, indicating an affinity for all its main ligands much higher than that of normal human red cell G6PD.