... Recently, high ecto-nucleotidase activity of several protozoan parasites -including Toxoplasma gondii, Entamoeba histolytica, Leishmania tropica, Leishmania amazonesis, Trypanosoma cruzi, Trypanosoma brucei, and Tritrichomonas foetus -has been shown to interfere with the extracellular signaling of the host and affect the virulence and pathogenesis of these organisms [8,9,10,11,12,13,14,15, 16,17]. Thus, it has been suggested that these enzymes play a role in the pathogenicity of these parasites by controlling the host cell response to infection, specifically by: (i) protecting the parasite from the cytolytic effects of extracellular ATP, (ii) regulating ectokinase substrate concentrations, (iii) preventing activation of signal transduction cascades associated with cellular injury, and (iv) facilitating cellular adhesion [18,19,20,21,22,23,24,25,26,27,28], reviewed in [28]. Among ecto-nucleosidases, Ecto-ATPases, or E-ATPases, are cell-surface enzymes that hydrolyze a range of extracellular nucleoside triphosphates (NTPs) and nucleoside diphosphates (NDPs). ...