Are purine bases enzymatically inserted into depurinated DNA in Escherichia coli

An enzyme activity to incorporate labeled dATP or dGTP preferentially into depurinated DNA, found in an extract of Escherichia coli, does not seem to represent "purine insertase," but may be ascribed to a combined action of DNA polymerase I and AP endonuclease(s) on the basis of the following findings. (1) The activity was found in polA+ but not in polA-cells. (2) The base moiety and the alpha-phosphate group of the nucleotide were equally incorporated into the DNA.