Purine nucleotide synthesis in Entamoeba histolytica: a preliminary study

Entamoeba histolytica, axenically grown, were unable to incorporate 14C-glycine into extractable purines, even after 16 hours incubation in the presence of this compound. Similarly, amoebas did not incorporate 14C-sodium formate into purines. Such data indicate a total absence of a de novo purine biosynthetic pathway in this amoeba. When amoebas were incubated in the presence of 3H-adenine and 3H-adenosine for one hour, considerable radioactivity was associated with AMP, ADP and ATP; no appreciable radioactivity was recoverable in the various guanine residues. However, after 16 hours incubation, a small percentage of guanine derivatives were labelled. Amoebas incubated for similar time periods in medium containing 3H-guanosine yielded high levels of radioactive guanosine and guanine nucleotides after one hour, and 3H-guanosine was not converted to adenine derivatives; after 16 hours incubation some 3H-guanosine was converted to adenine derivatives.