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Article
Elucidation of Aberrant Purine Metabolism: Application to Hypoxanthine-Guanine Phosphoribosylstransferase- and Adenosine Kinase-deficient Mutants, and IMP Dehydrogenase- and Adenosine Deaminase-inhibited Human Lymphoblasts
Biochimica et Biophysica Acta (BBA) - Nucleic Acids and Protein Synthesis
  • F. F. Snyder
  • Rebecca J. Trafzer, Cedarville University
  • M. S. Hershfield
  • J. E. Seegmiller
Document Type
Article
Publication Date
10-17-1980
DOI
http://dx.doi.org/10.1016/0005-2787(80)90123-9
PubMed ID
6108130
Abstract

We propose that the ratio of [14C]formate-labelled purine nucleosides and bases (both intra and extracellular) to nucleic acid purines provides, in exponentially growing cultures, a sensitive index for comparative studies of purine metabolism. This ratio was 4-fold greater for an HGPRT− mutant than for the parental HGPRT+ human lymphoblast line. The major components of the labelled nucleoside and base fraction were hypoxanthine and inosine. By blocking adenosine deaminase activity with coformycin we found that approx. 90% of inosine was formed directly from IMP rather than the route IMP → AMP → adenosine → inosine. The ratio of labelled base + nucleosides to nucleic acids was essentially unchanged for an AK− lymphoblast line and 2-fold greater than control for an HGPRT−-AK− line, demonstrating that a deficiency of adenosine kinase alone has little effect on the accumulation of purine nucleosides and bases. Although adenosine was a minor component of the nucleoside and base fraction, the adenosine fraction increased from 3 to 13% with the addition of coformycin to the HGPRT−-AK− line. In the parental and HGPRT− lines, adenosine was shown to be primarily phosphorylated rather than deaminated at concentrations less than 5 μM. Inhibition of IMP dehydrogenase activity by mycophenolic acid caused a 12- and 3-fold increase in the rate of production of labelled base and nucleoside in the parent and HGPRT− cells respectively. These results suggest that a mutationally induced partial deficiency in the activities converting IMP to guanine nucleotides may result in an increased catabolism of IMP.

Keywords
  • Purine metabolism,
  • hypoxanthine-guanine phosphoribosyltransferase deficiency,
  • adenosine kinase deficiency,
  • IMP dehydrogenase inhibition,
  • adenosine deaminase inhibition,
  • human lymphoblast
Citation Information
F. F. Snyder, Rebecca J. Trafzer, M. S. Hershfield and J. E. Seegmiller. "Elucidation of Aberrant Purine Metabolism: Application to Hypoxanthine-Guanine Phosphoribosylstransferase- and Adenosine Kinase-deficient Mutants, and IMP Dehydrogenase- and Adenosine Deaminase-inhibited Human Lymphoblasts" Biochimica et Biophysica Acta (BBA) - Nucleic Acids and Protein Synthesis Vol. 609 Iss. 3 (1980) p. 492 - 501 ISSN: 0006-3002
Available at: http://works.bepress.com/rebecca_gryka/28/