Carbon dioxide fixation in malaria—I. Kinetic studies in plasmodium lophurae

Abstract

1. 1. The avian malaria parasite Plasmodium lophurae, malaria-infected blood and normal duck erythrocytes, incubated in the presence of NaH C 14O 3 for periods up to 1 hr, incorporate C 14O 2 into keto, amino and other organic acids. 2. 2. The main stable products of CO 2 fixation for the parasites and parasitized cells are the amino acids glutamic and aspartic, whereas in the unifected red cell they are other organic acids, malic and citric. The alteration of metabolism of the parasitized blood cell is almost entirely due to the metabolism of the growing plasmodium. 3. 3. The labelign kinetics of the acids strongly suggest that oxaloacetate and α-ketoglutarate are intial products of CO 2 fixation of the malaria parasite. Subsequent to these keto acids, aspartate and glutamate are synthesized. The latter are those amino acids contributing most significantly to the increased free amino acid pool of the malaria-infected cell. Up to 1 hr, insignificant quantities of C 14 can be detected in RNA, DNA and protein fractions.