The utilization of purines and their ribosyl derivatives for the formation of adenosine triphosphate and guanosine triphosphate in the mature rabbit erythrocyte.

The finding that the purine portions of both adenosine triphosphate and guanosine triphosphate of the mature rabbit erythrocyte are not metabolically stable constituents of that cell, as is the heme of hemoglobin, suggested the possibility of a metabolic renewal of the nucleotides during the life of the cell (1, 2). The absence of any detectable utilization of sodium formate-Cl4 or of glycine-2-U4, in vitro, for purine nucleotide synthesis de vwvo suggested that the complete pathway of purine nucleotide formation from the small molecule precursors was not intact in this cell (3). The incorporation of sodium formate-Cl4 into the purine portions of both ATP and GTP, in the presence of 5-aminoI-ribosyl-4-imidazolecarboxamide, indicated that the mature rabbit erythrocyte, in vitro, has the capacity for carrying out the final steps of the pathway of purine nucleotide synthesis (3-5). Reports from several laboratories have suggested that tissues which lack the capacity for purine synthesis de novo, in vitro, may utilize preformed purines extensively for the formation of acidsoluble nucleotides and nucleic acids (6, 7). Lajtha and Vane (7) have proposed that an organ, such as the liver, which can synthesize purine nucleotides de novo may supply preformed purines to tissues, such as bone marrow, which have a limited capacity for purine ring formation but which may utilize preformed purines for purine nucleotide synthesis by the nucleotide pyrophosphorylase reaction (8, 9). This paper is concerned with the utilization of free purines and of the aglycones of purine nucleosides for the formation of the nucleoside triphosphates of adenine and guanine in the mature rabbit erythrocyte.