Enzymes of Nuclear Nicotinamide-Adenine Dinucleotide Metabolism

Changing the concentrations of NAD+ and histones did not alter significantly the observed inhibition. However, the inhibition was relieved by increasing amounts of DNA (Fig. 36). The effect of Actinomycin D was further studied by changing the order of addition of the various compounds (Fig. 3c). These results showed that when Actinomycin D was incubated with the polymerase before the addition of DNA the enzymic activity was strongly inhibited in spite of the presence of large amounts of DNA (50pg of calf thymus DNA/0.25 ml). These results suggest that Actinomycin D might interact with the polymerase in the presence of high concentrations of (NH4)2S04. We have been unable to demonstrate the direct interaction of Actinomycin D with thc polymerase.