The inhibition of deoxyribonucleotidyl transferase, DNAase and RNAase by sodium poly ethenesulfonic acid. Effect of the molecular weight of the inhibitor

• 1.

  1. The nature of the inhibition of DNA nucleotidyltransferase (EC 2.7.7.7) from KB cells (DNA polymerase) by poly ethenesulfonic acid (PES) and other polyanionic materials were examined. The inhibition was found to be competitive with the DNA used to prime the enzyme. The K₁ was found to be 1.72 ± 0.36 μg PES/ml for the 12 900 mol. wt. material in the range of zero to 10 μg inhibitor/ml. The inhibitory action of PES was strongly dependent on the molecular weight of the sample used in the range of 5000 to 13 000 and further increases in molecular weight did not seem to affect efficacy. Other polyanionic polymers, such as heparin, carboxymethyl cellulose, alginic acid, chitosan sulfate, RNA and chondroitin sulfate also inhibited this enzyme to varying degrees.

• 2.

  2. Spermine, which by itself inhibits the DNA polymerase, reversed the inhibition caused by PES. This is explained by the competition between DNA and PES for salt formation (and precipitation) with spermine.

• 3.

  3. The inhibition of pancreatic RNAase (EC 2.7.7.16) by PES exhibited a similar dependence on the molecular weight of the polymer as did the inhibition of DNA polymerase.

• 4.

  4. Addition of PES to DNAase I (EC 3.1.4.5) assays resulted in a bimodal, concentration-dependent curve. At intermediate concentrations the compound stimulated DNA hydrolysis, while at higher concentrations it inhibited.