Primary structure of the pyruvate phosphate dikinase in Entamoeba histolytica

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Although glycolysis is remarkably conserved among all organisms, parasitic protozoa without mitochondria, such as Entamoeba histolytica and Giardia lamblia, and some prokaryotes possess enzymes within this pathway that are characterized by the dependence of pyrophosphate (PPi) [1,2]. In E. histolytica and G. lamblia, one of these enzymes, the pyruvate phosphate dikinase (PPDK) functions in the direction of ATP synthesis [3,4]. It is a substitute for pyruvate kinase which is absent in these protozoa. Therefore, PPDK seems to be a suitable target of antiparasitic drugs since the enzyme is of primary importance for energy generation by the parasite and it is absent from the host. PPDK is also found in C4 plants like maize and Flaveria trinervia where it plays a role as one of the key enzymes in the photosynthetic pathway [5,6]. Here it catalyzes the synthesis of phosphoenolpyruvate (PEP) to pyruvate. Pyrophosphate-dependent enzymes like