KINETIC STUDIES ON DNA POLYMERASE

Pyrophosphorolysis and hydrolysis of DNA by DNA polymerase (deoxynucleosidetriphosphate:DNA deoxynucleotydyl-transferase, EC 2.7.7.7) from Escherichia coli were studied. Competition between pyrophosphate and hydroxyl ions is postulated. The Km values of pyrophosphate in pyrophosphorolysis and of hydroxyl ions in hydrolysis equaled the corresponding Ki values in hydrolysis and pyrophosphorolysis. Furthermore both reactions were inhibited competitively to the same degree by ATP and dATP. It is concluded that one active site is responsible for both pyrophosphorolysis and hydrolysis. These results, together with additional studies on the specificity of the polycondensation, lead to a model for the three functions of the enzyme. © 1968.