The optimal condition for the rat DNA polymerase β activity with (rA)n·(dT)12-18 as a template·primer was determined. The activity was remarkably affected by the concentration of the primer, (dT)12-18' and the mixing ratio of (dT)12-18 to (rA)n. DNA polymerase β requires higher primer concentration (Km=11.1 μM with respect to 3'-OH of the primer) than DNA polymerase γ (Km=0.04 μM) or oncornaviral DNA polymerase (Km=0.08 μM) and the enzyme represented the maximum activity in the base ratio of 2:1 with (dT)12-18 and (rA)n suggesting the difference in reaction mechanisms of these enzymes. Under the optimized conditions, the specific activity of the near homogeneous preparation of DNA polymerase β was 1,000,000 units per mg protein. © 1979 Information Retrieval Limited.
