Adenine and Adenosine Are Toxic to Human Lymphoblast Mutants Defective in Purine Salvage Enzymes

Mutants deficient in adenosine kinase or adenine phosphoribosyltransferase activities were selected from the WI-L2 line of human lymphoblasts. The adenosine kinase-deficient mutant was still as sensitive as its parent to growth inhibition caused by adenosine deaminase was inhibited. Similarly, the adenine phosphoribosyltransferase mutant remained sensitive to growth inhibition caused by adenine. Thus, the toxicity of adenine and adenosine to human lymphoblasts is not mediated by nucleotides to which they may be converted.