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Cardiac mitochondrial DNA polymerase-gamma is inhibited competitively and noncompetitively by phosphorylated zidovudine.

Abstract
Zidovudine (azidothymidine [AZT]) inhibits human immunodeficiency virus replication and reduces the severity of acquired immunodeficiency syndrome. A limiting side effect of AZT is a mitochondrial cardiac and skeletal myopathy in which the pharmacologically active derivative of AZT (AZT triphosphate) plays a critical role. The present study determined biochemical mechanisms of AZT-induced mitochondrial toxicity and identified AZT triphosphate as an inhibitor of DNA polymerase-gamma in vitro. Inhibition kinetics were defined using purified bovine cardiac mitochondrial DNA polymerase-gamma and AZT triphosphate in vitro. The Km for deoxythymidine triphosphate was 0.8 +/- 0.3 mumol/L. AZT triphosphate incubation with DNA polymerase-gamma in vitro resulted in mixed kinetics with a competitive Ki of 1.8 +/- 0.2 mumol/L and a noncompetitive Ki' of 6.8 +/- 1.7 mumol/L. These Ki and Ki' values were strikingly higher than values for retroviral reverse transcriptase but lower than values for other cellular DNA polymerases. These data support previous molecular and morphological findings in clinical AZT mitochondrial myopathy and in models of AZT myopathy in vivo. Biochemical findings suggest that inhibition of mitochondrial DNA polymerase-gamma may be integral to the pathogenesis of AZT-induced myopathy.
AuthorsW Lewis, J F Simpson, R R Meyer
JournalCirculation research (Circ Res) Vol. 74 Issue 2 Pg. 344-8 (Feb 1994) ISSN: 0009-7330 [Print] United States
PMID8293572 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
Chemical References
  • Dideoxynucleotides
  • Thymine Nucleotides
  • Zidovudine
  • zidovudine triphosphate
  • DNA Polymerase III
  • thymidine 5'-triphosphate
Topics
  • Animals
  • Cattle
  • DNA Polymerase III (antagonists & inhibitors)
  • Dideoxynucleotides
  • Kinetics
  • Mitochondria, Heart (enzymology)
  • Phosphorylation
  • Thymine Nucleotides (metabolism, pharmacology)
  • Zidovudine (analogs & derivatives, pharmacology)

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