Interactions between Energy Metabolism and Adenine Nucleotide Metabolism in Human Lymphoblasts

Abstract

Adenine nucleotides play an important role in the transfer of chemical energy for metabolic processes. In addition, adenine nucleotide degradation can be a major source of purine bases formed during certain kinds of metabolic stress. These two properties of adenine nucleotides may be related. Fructose and 2-deoxyglucose can produce elevated levels of purines in vivo (1), in perfused organs (2), and in cultured cells (3,4). The mechanism of nucleotide degradation caused by fructose or 2-deoxyglucose involves the utilization of ATP to form a slowly metabolized hexose phosphate which accumulates and decreases the intracellular concentration of inorganic phosphate (1–4). AMP deaminase, which is normally inhibited by phosphate, becomes more active when the phosphate concentration decreases and adenine nucleotides are broken down by the reactions: AMP → IMP + NH₃; IMP → inosine + PO ^2-₄ . There also exists another pathway for adenine nucleotide degradation catalyzed by the enzymes purine 5′-nucleotidase and adenosine deaminase: AMP → adenosine + PO ^2-₄ ; adenosine → inosine + NH₃.