Purine nucleotide synthesis in adrenal chromaffin cells

The synthesis of purine nucleotides from the salvage precursors adenine and adenosine, and from the de novo precursors formate and glycine, was studied in isolated adrenal chromaffin cells. Both [8-14C]adenine and [8-14C]adenosine from extracellular medium are effectively incorporated into intracellular nucleotides. [14C]Formate and [U-14C]glycine are also incorporated, but de novo synthesis is clearly lower than synthesis from salvage precursors, although similar to de novo synthesis in liver. The enzymes responsible for adenine and adenosine salvage, adenine phosphoribosyltransferase and adenosine kinase, were purified about 1,500-fold. Both enzymes are mainly cytosolic and exhibit a similar molecular weight of around 42,000. The results suggest that chromaffin cells can replenish their intracellular nucleotides lost during the secretory event by an active synthesis from salvage and de novo precursors.