Glucose-6-phosphate dehydrogenase activity of the malaria parasite Plasmodium falciparum

Schizonts of Plasmodium falciparum, grown either in normal or glucose-6-phosphate dehydrogenase (G6PDH) deficient human red cells, contain an electrophoretically slow-moving form of G6PDH. The slow mobility of the G6PDH in non-dissociating polyacrylamide gels is due to its large size (Mr ca. 450,000) rather than to its charge. The activity of this enzyme was less than 10% of normal red cell G6PDH. These characteristics of the parasite-associated G6PDH were unaltered when parasites were grown in red cells from a G6PDH A+B+ heterozygote or following the introduction of a heterologous G6PDH into resealed ghosts. Differential absorption of the parasite-associated and red cell G6PDHs was demonstrated with antisera containing antibodies to red cell G6PDH. These studies show that a novel form of G6PDH is associated with P. falciparum in normal red cells without the requirements for induction by one or several cycles of multiplication in G6PDH deficient red cells.