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Tenofovir diphosphate is a poor substrate and a weak inhibitor of rat DNA polymerases alpha, delta, and epsilon*

Gabriel Birkus1, Miroslav Hájek, Pavel Kramata

  • 1Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic. Gabriel_Birkus@gilead.com

Antimicrobial Agents and Chemotherapy
|April 18, 2002
PubMed

Insights

Tenofovir diphosphate (PMPApp) weakly inhibits DNA polymerases alpha, delta, and epsilon. Its DNA incorporation is significantly less efficient than dATP, indicating limited therapeutic potential as a direct polymerase inhibitor.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Virology

Background:

  • Tenofovir diphosphate (PMPApp) is an active metabolite of tenofovir, a nucleotide analog reverse transcriptase inhibitor.
  • Understanding its interaction with host DNA polymerases is crucial for assessing potential toxicity and off-target effects.

Purpose of the Study:

  • To investigate the inhibitory potential of Tenofovir diphosphate (PMPApp) against human DNA polymerases alpha, delta, and epsilon.
  • To quantify the efficiency of PMPApp incorporation into DNA compared to deoxyadenosine triphosphate (dATP).

Main Methods:

  • Enzyme kinetics assays were performed to determine the inhibition constants (Ki) of PMPApp relative to dATP for DNA polymerases alpha, delta, and epsilon.
  • DNA synthesis assays were used to measure the incorporation efficiency of PMPApp compared to dATP.

Main Results:

  • PMPApp demonstrated weak inhibition against DNA polymerases alpha, delta, and epsilon, with Ki values significantly higher than dATP's Km.
  • The incorporation of PMPApp into DNA was approximately 1,000-fold less efficient than dATP.
  • Km values for PMPApp incorporation were substantially higher (350- to 2,155-fold) than those for dATP across the studied polymerases.

Conclusions:

  • Tenofovir diphosphate (PMPApp) exhibits limited inhibitory activity against key replicative DNA polymerases.
  • The low incorporation efficiency of PMPApp into DNA suggests a low risk of direct genotoxicity through this mechanism.

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