Kinetic Flux Profiling Elucidates Two Independent Acetyl-CoA Biosynthetic Pathways in Plasmodium falciparum
Kinetic Flux Profiling Elucidates Two Independent Acetyl-CoA Biosynthetic Pathways in Plasmodium falciparum
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DOI：
10.1074/jbc.m113.503557
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发表时间：
2013-12-20
影响因子：
4.8
通讯作者：
Llinas, Manuel
中科院分区：
文献类型：
--
作者：
Cobbold, Simon A.;Vaughan, Ashley M.;Llinas, Manuel
背景：疟原虫的乙酰辅酶A生物合成途径尚不清楚。结果如下：在缺乏功能性丙酮酸脱氢酶（PDH）复合物的寄生虫中进行的C-13标记实验表明，PDH对乙酰辅酶A库没有显著贡献。结论：乙酰辅酶A合成主要来源于类PDH酶和乙酰辅酶A合成酶。重要性：合成乙酰辅酶A的两条途径似乎有不同的功能。疟疾寄生虫恶性疟原虫依赖葡萄糖来满足其在血液阶段发育的能量需求。虽然糖酵解是寄生虫中最好理解的途径之一，但尚不清楚葡萄糖代谢是否明显有助于三羧酸代谢（TCA）循环和脂肪酸生物合成所需的乙酰辅酶A池。恶性疟原虫具有丙酮酸脱氢酶（PDH）复合物，该复合物定位于顶质体（一种专门的四重膜细胞器），这表明可能存在单独的乙酰辅酶A池。在此，我们分析PDH缺陷型寄生虫使用快速稳定同位素标记，并表明PDH不明显有助于乙酰辅酶A合成，三羧酸代谢，或脂肪酸合成的血液阶段寄生虫。相反，我们发现乙酰辅酶A的需求是通过PDH样酶提供的，并提供证据表明支链酮酸脱氢酶（BCKDH）复合物正在执行这一功能。我们还表明，乙酰辅酶A合成酶可以是一个显着的贡献者乙酰辅酶A的生物合成。有趣的是，PDH样途径有助于葡萄糖衍生的乙酰辅酶A的TCA循环在一个阶段独立的过程中，而anapleurotic碳进入TCA循环通过阶段依赖性磷酸烯醇式丙酮酸羧化酶/磷酸烯醇式丙酮酸羧激酶的过程中，随着寄生虫的成熟而减少。虽然PDH缺陷型寄生虫没有血液阶段的生长缺陷，但它们无法超越寄生蚊阶段的卵囊阶段。
Background: The acetyl-CoA biosynthetic pathways of the malaria parasite are unclear. Results: C-13-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.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.