Catalyzes the excision of an oxidatively damaged form of guanine (7,8-dihydro-8-oxoguanine = 8-oxoG) from DNA (PubMed:10521423, PubMed:19446526). Also cleaves the DNA backbone at apurinic/apyrimidinic sites (AP sites) (PubMed:10521423, PubMed:19446526). Has little specificity for the base opposite oxoG (PubMed:10521423). 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(+) Optimum pH is 8.5. Contains two domains separated by the central HhH motif. The C-terminal domain undergoes a conformational change upon DNA binding. Belongs to the type-2 OGG1 family.