Involved in base excision repair of DNA damaged by oxidation or by mutagenic agents. Acts as DNA glycosylase that recognizes and removes damaged bases. Acts on oxidized purines, such as 7,8-dihydro-8-oxoguanine (8-oxoG) when paired with C, G or T. Has AP (apurinic/apyrimidinic) lyase activity and introduces nicks in the DNA strand. Cleaves the DNA backbone by beta-delta elimination to generate a single-strand break at the site of the removed base with both 3'- and 5'-phosphates. Hydrolysis of DNA containing ring-opened 7-methylguanine residues, releasing 2,6-diamino-4-hydroxy-5-(N-methyl)formamidopyrimidine. 2'-deoxyribonucleotide-(2'-deoxyribose 5'-phosphate)-2'-deoxyribonucleotide-DNA = a 3'-end 2'-deoxyribonucleotide-(2,3-dehydro-2,3-deoxyribose 5'-phosphate)-DNA + a 5'-end 5'-monophospho-2'-deoxyribonucleoside-DNA + H(+) Binds 1 zinc ion per subunit. Monomer. Loss of excision of 8-oxoG from dsDNA. No significant growth in the presence of 3 mM H(2)O(2). 4-fold increase in mutation frequency upon plating on rifampicin (mutator phenotype); an increase in A to G and C to G mutations is seen. Belongs to the FPG family.