Differential Inhibition of DNA Polymerases of Calf Thymus by 9-β-D-Arabinofranosyladenine-5′-triphosphate1

Abstract

The effect of 9-β-D-arabinofranosyladenine-5′-tnphosphate (araATP) on the reactions of DNA polymerases α and β [E.C. 2.7.7.7] purified from calf thymus was examined. The reaction of DNA polymerase α was shown to be more sensitive to the inhibition than that of DNA polymerase β. The K₁ value of DNA polymerase β for araATP was 45 μM; 15 times higher than that of DNA polymerase α (3 μM). The mode of inhibition by araATP was essentially competitive to deoxyadenosine triphosphate (dATP) in the reactions catalyzed by both DNA polymerase α and β using activated DNA as a template-primer. However, in the reactions of the α-enzyme, araATP also inhibited the incorporation of deoxyribonucleotides other than dATP non-competitively.