De Novo Synthesis of Purine Nucleotides in Human Peripheral Blood Platelets

Abstract

Human blood platelets were gtudied for the presence of the pathway of de novo synthesis of purine nucleotides. 8 x 108 cells were incubated for 2.5 h at 37°C in 2 ml of Eagle’s Minimal Essential Medium containing Earle’s Balanced Salt Solution, 15% fetal calf serum and 20 μCi sodium [14C] formate (59 mCi/mmole). Platelets were found to incorporate 14C into total purines at a slow but detectable rate of 50–70 pmoles/8 x 108 cells/2.5 h. This incorporation was inhibited by approximately 80% at 10 mM azaserine and by 60% at 0.1 mM adenine. Adenine is known to affect the rate of purine synthesis de novo through the activity of phosphoribosylpyrophosphate amidotransferase, the first committed enzyme of this pathway. The results suggest the presence of the complete pathway of de novo synthesis of purine nucleotides in normal human peripheral blood platelets.