Differential inhibition of DNA polymerases of calf thymus by 9-beta-D-arabinofuranosyladenine-5'-triphosphate.

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