In addition to these proteins, several other enzymes are involved in bacterial DNA replication. 1  DNA Polymerase-DNA Polymerase I (Pol I) was the first enzyme discovered with polymerase activity, and it is the best characterized enzyme. 2  5' to 3' elongation (polymerase activity). 3  3' to 5' exonuclease (proof-reading activity). 4  5' to 3' exonuclease ....