Glucose metabolism and its controlling mechanisms in entamoeba histolytica

Abstract

Entamoeba histolytica lacks the genes encoding the enzymes of the Krebs cycle and oxidative phosphorylation; therefore, glycolysis is the main pathway for ATP supply and for providing carbon skeleton precursors for the synthesis of macromolecules. External glucose is metabolized through a fermentative glycolysis producing mainly ethanol and, to a lower extent, acetate as end products. The pathway in the parasite deviates in several aspects from the typical glycolysis present in mammals and yeasts, for instance, (1) the use of pyrophosphate as high- energy phosphate donor in several reactions; (2) the feasibility of thermodynamic reversibility of all pathway reactions under physiological conditions; and (3) the presence of fermentative enzymes similar to those of anaerobic bacteria. These and other enzyme peculiarities impose different mechanisms of control of the glycolytic fermentative flux in the parasite compared to the highly allosterically regulated glycolysis in other eukaryotic cells. In this chapter, we summarize the previous and current knowledge of the carbohydrate metabolism in E. histolytica and analyze its underlying controlling mechanisms by applying the fundamentals of metabolic control analysis (MCA).