Coenzyme A requirement of malaria parasites: enzymes of coenzyme A biosynthesis in normal duck erythrocytes and erythrocytes infected with Plasmodium lophurae.

Abstract

Normal Cell Isolation. Detailed procedures for maintaining heavy synchronous infections of these parasites and for isolating erythrocytes or host-free parasites have been described (6, 7). Giemsa-stained thin blood films were used to determine the extent of parasitemia (expressed as the total number of parasites per 100 erythrocytes) and the development stage of the parasite population. The erythrocytes and cell-free parasites used in these studies were obtained from control ducks, ducks infected with small parasites at the uninucleate trophozoite stage of development (4th day after passage), and ducks infected with larger parasites at the multinucleate schizont stage of infection (5th day after passage). Only blood with heavy infections (90-130%) and with 80-90% of either uninucleate or multinucleate parasites was used.Enzyme Preparation. All operations were carried out at 4°. Washed, packed erythrocytes from control and infected ducks or host-free parasites were susl)ended in four times their packed cell volume of 0.05 M Tris HCl buffer, pH 7.5, and passed through a French pressure cell at 8000 lbs./inch2 (562.4 kg/cm2). Wet-mount slides of homogenized cells were observed with a microscope to estimate the degree of cell breakage. The homogenized cell suspensions were centrifuged at 13,000 X g for 0.5 hr in a Sorvall RC2-B refrigerated centrifuge, and the supernatants from this step were assayed directly for enzyme activity.Assays. Phosphopantothenoylcysteine synthetase (pantothenate 4'-phosphate: L-cysteine ligase; EC 6.3.2.5), phospho-

The Human Malaria Parasite Plasmodium falciparum Is Not Dependent on Host Coenzyme A Biosynthesis

“…Trager (5, 6) later demonstrated, however, that CoA, and not pantothenate, stimulated exoerythrocytic growth of the intraerythrocytic stage of P. lophurae, and proposed that avian malaria parasites are incapable of metabolizing pantothenate to CoA, and instead rely on CoA synthesized by the host erythrocyte. In support of this proposal, CoA biosynthesis enzymes are readily detectable in duck erythrocytes, but appear to be absent from P. lophurae parasites isolated from their host erythrocyte (7,8). Pantothenate is therefore required by the P. lophurae-infected duck erythrocyte for CoA biosynthesis within the host cell and not the parasite itself.…”

“…In support of this proposal, CoA biosynthesis enzymes are readily detectable in duck erythrocytes, but appear to be absent from P. lophurae parasites isolated from their host erythrocyte (7,8). Pantothenate is therefore required by the P. lophurae-infected duck erythrocyte for CoA biosynthesis within the host cell and not the parasite itself.…”

Provitamin B 5 (Pantothenol) Inhibits Growth of the Intraerythrocytic Malaria Parasite

“…In Plasmodium-infected avian erythrocytes, pantothenate is converted to CoA in the erythrocyte compartment and the CoA is then taken up across the parasite plasma membrane (8). By contrast, in P. falciparum-infected human erythrocytes pantothenic acid is taken up by and metabolized within the parasite (15,16).…”

“…Biochemical analyses on both uninfected and Plasmodium lophurae-infected duck erythrocytes, as well as on P. lophurae parasites isolated from their host erythrocytes, revealed that duck erythrocytes have all of the enzymes for CoA biosynthesis, whereas the intraerythrocytic parasites themselves have none (5,8). This led to the proposal that the parasite takes up preformed CoA from the host cell.…”

“…it was shown that in chickens infected with Plasmodium gallinaceum and either fed on a pantothenic aciddeficient diet or dosed orally with pantothenic acid analogs, there was significant suppression of the proliferation of bloodstage parasites (7). Similarly, in early in vitro culture experiments Trager showed that a pantothenate analog caused a marked reduction in the proliferation of a number of different malaria parasite strains, including the most virulent of the human malaria parasites, P. falciparum (18,19).Biochemical analyses on both uninfected and Plasmodium lophurae-infected duck erythrocytes, as well as on P. lophurae parasites isolated from their host erythrocytes, revealed that duck erythrocytes have all of the enzymes for CoA biosynthesis, whereas the intraerythrocytic parasites themselves have none (5,8). This led to the proposal that the parasite takes up preformed CoA from the host cell.…”