Utilization of ammonium ions for purine precursor synthesis in soluble extracts of Ehrlich ascites cells

In extracts of Ehrlich ascites cells the synthesis of α-N-formylglycinamide ribonucleotide (FGAR), an early intermediate in de novo purine synthesis, is enhanced by the presence of ammonium ions. Under these experimental conditions glutamine participation in FGAR formation is not obligatory. Ribonucleotides, deoxyribonucleotides, and purine analogues which inhibit glutamine-dependent FGAR synthesis also inhibit ammonium-ion-dependent FGAR synthesis. 3′-Ribonucleotides do not inhibit purine precursor formation from ammonium ions or from glutamine.