Endonuclease IV can act on a variety of oxidative damage in DNA

The enzyme is apurinic/apyrimidinic (AP) endonuclease that will hydrolyse intact AP sites in DNA. AP sites are cleaved at the first phosphodiester bond that is 5´ to the lesion leaving a hydroxyl group at the 3´ terminus and a deoxyribose 5´-phosphate at the 5´ terminus. The enzyme also has a 3´ -diesterease activity and can release phosphoglycoaldehyde, intact deoxyribose 5-phosphate and phosphate from the 3´ end of DNA.