Entamoeba histolytica: Uptake of purine bases and nucleosides during axenic growth

A comparison was made of the uptake mechanisms of selected purine bases and nucleosides by axenically grown Entamoeba histolytica. Adenine, adenosine, and guanosine were taken up, in part, by a “carrier”-mediated system. Guanine, hypoxanthine, and inosine entered amoebas via diffusion. Inhibitor studies support the presence of individual transport sites for adenine-adenosine and adenosine-guanosine. Additional sites for transport of adenine, adenosine, and guanosine are implied by “non-productive binding” involving guanine, hypoxanthine, and inosine. Uptake of adenine, adenosine, and guanosine was reduced by iodoacetate and N-ethylmaleimide. Ribose failed to inhibit uptake of purine nucleosides.