Adenosine Metabolism in Permanent Lymphocyte Lines and in Erythrocytes of Patients with the Lesch-Nyhan Syndrome
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Adenosine metabolism of mammalian lymphocytes is of particular interest since the discovery of Giblett that hereditary severe combined immunodeficiency is linked with adenosine deaminase deficiency (1). In mammalian cells adenosine is phosphorylated to adenylate (AMP) or deaminated to inosine (Fig. 1 reaction 2), which is converted to hypoxanthine. Cells derived from patients with the Lesch Nyhan (L.N.) syndrome are deficient in hypoxanthine guanine phosphoribosyltransferase (HGPRT, EC 22.214.171.124) and therefore cannot convert hypoxanthine to inosinate (IMP). Consequently these cells provide a convenient model system to assess the importance of adenosine as a source of purine ribonucleotides in mammalian cells. The phosphorylation of adenosine to adenylate (AMP) is catalysed by adenosine kinase (AK, EC 126.96.36.199, Fig. 1 reaction 1) ; this pathway could serve as an additional means of purine salvage. Since adenosine is toxic to mammalian cells in culture (2), and plays a role in suppressing the proliferative response of lymphocytes to PHA (3), the present study of the metabolic fate of adenosine was carried out in cultured lymphocytes and in erythrocytes obtained from normal subjects and patients with the L.N. syndrome. The purpose of this study is to determine whether in HGPRT deficient cells, adenosine could indeed serve as an alternative source of purine ribonucleotides.
KeywordsAdenine Nucleotide Adenosine Deaminase Control Cell Line Adenosine Kinase Adenine Phosphoribosyltransferase
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