Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536 CNRS, France.
J Biol Chem. 2010 Oct 15;285(42):32312-24. doi: 10.1074/jbc.M110.124917. Epub 2010 Aug 11.
Trypanosoma brucei is a parasitic protist that undergoes a complex life cycle during transmission from its mammalian host (bloodstream forms) to the midgut of its insect vector (procyclic form). In both parasitic forms, most glycolytic steps take place within specialized peroxisomes, called glycosomes. Here, we studied metabolic adaptations in procyclic trypanosome mutants affected in their maintenance of the glycosomal redox balance. T. brucei can theoretically use three strategies to maintain the glycosomal NAD(+)/NADH balance as follows: (i) the glycosomal succinic fermentation branch; (ii) the glycerol 3-phosphate (Gly-3-P)/dihydroxyacetone phosphate (DHAP) shuttle that transfers reducing equivalents to the mitochondrion; and (iii) the glycosomal glycerol production pathway. We showed a hierarchy in the use of these glycosomal NADH-consuming pathways by determining metabolic perturbations and adaptations in single and double mutant cell lines using a combination of NMR, ion chromatography-MS/MS, and HPLC approaches. Although functional, the Gly-3-P/DHAP shuttle is primarily used when the preferred succinate fermentation pathway is abolished in the Δpepck knock-out mutant cell line. In the absence of these two pathways (Δpepck/(RNAi)FAD-GPDH.i mutant), glycerol production is used but with a 16-fold reduced glycolytic flux. In addition, the Δpepck mutant cell line shows a 3.3-fold reduced glycolytic flux compensated by an increase of proline metabolism. The inability of the Δpepck mutant to maintain a high glycolytic flux demonstrates that the Gly-3-P/DHAP shuttle is not adapted to the procyclic trypanosome context. In contrast, this shuttle was shown earlier to be the only way used by the bloodstream forms of T. brucei to sustain their high glycolytic flux.
布氏锥虫是一种寄生原生动物,在从哺乳动物宿主(血液形式)传播到昆虫载体的中肠(前循环形式)的过程中经历复杂的生命周期。在前循环形式中,大多数糖酵解步骤发生在专门的过氧化物酶体(称为糖酶体)中。在这里,我们研究了在维持糖酶体氧化还原平衡方面受到影响的前循环锥虫突变体的代谢适应。布氏锥虫理论上可以使用三种策略来维持糖酶体 NAD(+)/NADH 平衡,如下所示:(i)糖酶体琥珀酸发酵分支;(ii)甘油-3-磷酸(Gly-3-P)/二羟丙酮磷酸(DHAP)穿梭,将还原当量转移到线粒体;和(iii)糖酶体甘油生产途径。我们通过使用 NMR、离子色谱-MS/MS 和 HPLC 方法的组合,在单个和双突变细胞系中确定代谢扰动和适应,显示了这些糖酶体 NADH 消耗途径的使用优先级。尽管功能正常,但 Gly-3-P/DHAP 穿梭主要在前循环中琥珀酸发酵途径在 Δpepck 敲除突变细胞系中被废除时使用。在这两种途径(Δpepck/(RNAi)FAD-GPDH.i 突变体)缺失的情况下,甘油生产被使用,但糖酵解通量减少了 16 倍。此外,Δpepck 突变细胞系的糖酵解通量降低了 3.3 倍,脯氨酸代谢增加了来补偿。Δpepck 突变体无法维持高糖酵解通量表明 Gly-3-P/DHAP 穿梭不适应前循环锥虫的环境。相比之下,早些时候已经表明,这种穿梭是布氏锥虫血液形式维持其高糖酵解通量的唯一途径。