Flux Analysis of the Trypanosoma brucei Glycolysis Based on a Multiobjective-Criteria Bioinformatic Approach

Abstract

Trypanosoma brucei is a protozoan parasite of major of interest in discovering new genes for drug targets. This parasite alternates its life cycle between the mammal host(s) (bloodstream form) and the insect vector (procyclic form), with two divergent glucose metabolism amenable to in vitro culture. While the metabolic network of the bloodstream forms has been well characterized, the flux distribution between the different branches of the glucose metabolic network in the procyclic form has not been addressed so far. We present a computational analysis (called Metaboflux) that exploits the metabolic topology of the procyclic form, and allows the incorporation of multipurpose experimental data to increase the biological relevance of the model. The alternatives resulting from the structural complexity of networks are formulated as an optimization problem solved by a metaheuristic where experimental data are modeled in a multiobjective function. Our results show that the current metabolic model is in agreement with experimental data and confirms the observed high metabolic flexibility of glucose metabolism. In addition, Metaboflux offers a rational explanation for the high flexibility in the ratio between final products from glucose metabolism, thsat is, flux redistribution through the malic enzyme steps.

Cytosolic NADPH Homeostasis in Glucose-starved Procyclic Trypanosoma brucei Relies on Malic Enzyme and the Pentose Phosphate Pathway Fed by Gluconeogenic Flux

“…Thus, an increase of NADPH demand may lead to an increase of acetate production from glucose metabolism. The suggested role of MEc is consistent with a recent in silico analysis of flux distribution between the different metabolic branches using a multiobjective-criteria bioinformatics approach (59). The simulations predict that ME activity is primarily responsible for the high flexibility observed for the excreted succinate/acetate ratio (33,54).…”

Contribution of Pyruvate Phosphate Dikinase in the Maintenance of the Glycosomal ATP/ADP Balance in the Trypanosoma brucei Procyclic Form

“…1A). In this context, the role of PPDK is probably to participate in the maintenance of the glycosomal ATP/ADP balance, as proposed before (6,7).…”

“…1A), however, this has not been experimentally investigated so far (7,49). To address this question, we generated a double ⌬ppdk/⌬pepck knock-out mutant by deleting the PEPCK gene in the PPDK null background (⌬ppdk).…”

Combining reverse genetics and nuclear magnetic resonance‐based metabolomics unravels trypanosome‐specific metabolic pathways

“…data). A multiobjective-criteria bioinformatics analysis of the flux distribution of the procyclic glucose metabolism showed that this high flexibility is due to flux redistribution from the succinate branch to the acetate branch through the NADP + -dependent malic enzymes (steps 6a, 6b) (Ghozlane et al, 2012). The procyclic trypanosomes express two malic enzyme isoforms: the cytosolic malic enzyme (MEc) isoform, which is synergistically essential with the pentose phosphate pathway for NADPH production; and the essential mitochondrial malic enzyme (Mem) isoform (Leroux et al, 2011;Allmann et al, 2013).…”