In vivo identification of the steps that control energy metabolism and survival of Entamoeba histolytica.

The steps that control the Entamoeba histolytica glycolytic flux were here identified by elasticity analysis, an experimental approach of metabolic control analysis. The concentrations of glycolytic metabolites were gradually varied in live trophozoites by (a) feeding with different glucose concentrations and (b) inhibiting the final pathway steps; in parallel, the changes in the pathway flux were determined. From the metabolite concentrationflux relationship, the elasticity coefficients of individual or groups of pathway reactions were determined and used to calculate their respective degrees of control on the glycolytic flux (flux control coefficients). The results indicated that the pathway flux was mainly controlled (72-86%) by the glucose transport/hexokinase/glycogen degradation group of reactions and by bifunctional aldehyde-alcohol dehydrogenase (ADHE; 18%). Further, inhibition of the first pathway reactions with 2-deoxyglucose (2DOG) decreased the glycolytic flux and ATP content by 75% and 50%, respectively. Cell viability was also decreased by 2DOG (25%) and more potently (50%) by 2DOG plus the ADHE inhibitor tetraethylthiuram disulfide (disulfiram). Biosate as an alternative carbon (amino acid) source was unable to replace glucose for ATP supply, which indicated that glucose was the main nutrient for amoebal ATP synthesis and survival. These results indicated that glycolysis in the parasite is mainly controlled by the initial pathway reactions and that their inhibition can decrease the parasite energy load and survival.