title: Kinetic flux profiling elucidates two independent acetyl-CoA biosynthetic pathways in Plasmodium falciparum.
abstract: 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.
authors.affiliation: From the Department of Biochemistry and Molecular Biology and Center for Infectious Disease Dynamics, Pennsylvania State University, State College, Pennsylvania 16802.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Cobbold
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Vaughan
authors.forename: Ian A
authors.initials: IA
authors.lastname: Lewis
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Painter
authors.forename: Nelly
authors.initials: N
authors.lastname: Camargo
authors.forename: David H
authors.initials: DH
authors.lastname: Perlman
authors.forename: Matthew
authors.initials: M
authors.lastname: Fishbaugher
authors.forename: Julie
authors.initials: J
authors.lastname: Healer
authors.forename: Alan F
authors.initials: AF
authors.lastname: Cowman
authors.forename: Stefan H I
authors.initials: SH
authors.lastname: Kappe
authors.forename: Manuel
authors.initials: M
authors.lastname: Llinás
mesh_terms: D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / Q000378:metabolism; D000106:Acetate-CoA Ligase / Q000378:metabolism; D000105:Acetyl Coenzyme A / Q000096:biosynthesis*; D000818:Animals; D000852:Anopheles / Q000469:parasitology; D002952:Citric Acid Cycle; D005227:Fatty Acids / Q000378:metabolism; D007700:Kinetics; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000378:metabolism; D010730:Phosphoenolpyruvate Carboxylase / Q000378:metabolism; D010963:Plasmodium falciparum / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism*; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D015800:Protozoan Proteins; D011768:Pyruvate Dehydrogenase Complex; D000105:Acetyl Coenzyme A; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D010730:Phosphoenolpyruvate Carboxylase; D019764:Phosphoenolpyruvate Carboxykinase (ATP); D000106:Acetate-CoA Ligase
keywords: Acetate; Acetyl Coenzyme A; Glycolysis; Malaria; Phosphoenolpyruvate Carboxykinase; Plasmodium; Pyruvate Dehydrogenase Complex; Tricarboxylic Acid (TCA) Cycle