Plasmodium falciparum: Properties of an α-like DNA polymerase, the key enzyme in DNA synthesis

An α-like DNA polymerase has been identified and characterized in the extracts from the malarial parasite Plasmodium falciparum. The enzyme is sensitive to the specific inhibitors of α-DNA polymerase, N-ethylmaleimide and aphidicolin, and is cell-cycle specific. High activity has been found in the schizont, is lower in trophozoites, and has only negligible activity in the ring form. The enzyme has a molecular weight of about M_r 100,000-103,000 estimated by detecting activity in SDS-polyacrylamide electrophoresis and by Bio-Gel filtration. Another active band of a molecular _r 68,000 was detected by SDS electrophoresis when the enzyme was stored for 2 months at -20 °C. The catalytic activity of parasite enzyme was optimal between pH 8 and pH 9. The apparent Michaelis Constant for dTTP was 4.3 μM.