Kinetic Flux Profiling Elucidates Two Independent Acetyl-CoA Biosynthetic Pathways in Plasmodium falciparum

• Published in: The Journal of biological chemistry Vol. 288; no. 51; pp. 36338 - 36350
• Main Authors: Cobbold, Simon A., Vaughan, Ashley M., Lewis, Ian A., Painter, Heather J., Camargo, Nelly, Perlman, David H., Fishbaugher, Matthew, Healer, Julie, Cowman, Alan F., Kappe, Stefan H.I., Llinás, Manuel
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 20.12.2013; American Society for Biochemistry and Molecular Biology
• Subjects: 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) - metabolism; Acetate; Acetate-CoA Ligase - metabolism; Acetyl Coenzyme A; Acetyl Coenzyme A - biosynthesis; Animals; Anopheles - parasitology; Citric Acid Cycle; Fatty Acids - metabolism; Glycolysis; Kinetics; Malaria; Metabolism; Phosphoenolpyruvate Carboxykinase; Phosphoenolpyruvate Carboxykinase (ATP) - metabolism; Phosphoenolpyruvate Carboxylase - metabolism; Plasmodium; Plasmodium falciparum - metabolism; Protozoan Proteins - metabolism; Pyruvate Dehydrogenase Complex; Pyruvate Dehydrogenase Complex - metabolism; Tricarboxylic Acid (TCA) Cycle; Plasmodium; Pyruvate Dehydrogenase Complex; Malaria; Phosphoenolpyruvate Carboxykinase; Glycolysis; Acetate; Acetyl Coenzyme A; Tricarboxylic Acid (TCA) Cycle
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M113.503557

The malaria parasite Plasmodium falciparum depends on glucose to meet its energy requirements during blood-stage development. Although glycolysis is one of the best understood pathways in the parasite, it is unclear if glucose metabolism appreciably contributes to the acetyl-CoA pools required for tricarboxylic acid metabolism (TCA) cycle and fatty acid biosynthesis. P. falciparum possesses a pyruvate dehydrogenase (PDH) complex that is localized to the apicoplast, a specialized quadruple membrane organelle, suggesting that separate acetyl-CoA pools are likely. Herein, we analyze PDH-deficient parasites using rapid stable-isotope labeling and show that PDH does not appreciably contribute to acetyl-CoA synthesis, tricarboxylic acid metabolism, or fatty acid synthesis in blood stage parasites. Rather, we find that acetyl-CoA demands are supplied through a “PDH-like” enzyme and provide evidence that the branched-chain keto acid dehydrogenase (BCKDH) complex is performing this function. We also show that acetyl-CoA synthetase can be a significant contributor to acetyl-CoA biosynthesis. Interestingly, the PDH-like pathway contributes glucose-derived acetyl-CoA to the TCA cycle in a stage-independent process, whereas anapleurotic carbon enters the TCA cycle via a stage-dependent phosphoenolpyruvate carboxylase/phosphoenolpyruvate carboxykinase process that decreases as the parasite matures. Although PDH-deficient parasites have no blood-stage growth defect, they are unable to progress beyond the oocyst phase of the parasite mosquito stage. Background: The acetyl-CoA biosynthetic pathways of the malaria parasite are unclear. Results:13C-Labeling experiments in parasites lacking a functional pyruvate dehydrogenase (PDH) complex show that the PDH does not contribute significantly to the acetyl-CoA pool. Conclusion: The majority of acetyl-CoA biosynthesis in the parasite derives from a PDH-like enzyme and acetyl-CoA synthetase. Significance: The two routes for acetyl-CoA synthesis appear to have separate functions.