FPG-type (PS51066) is a formamidopyrimidine-DNA glycosylase. A DNA glycosylase from bacteria prefers to use oxidized purines, like 7,8-dihydro-8-oxoguanine (8-oxoG), to find and get rid of damaged bases. The oxidized guanine is cut out by nucleophilic substitution of the N-terminal proline at C1'. The aminal intermediate that is subsequently generated endures β and δ elimination, resulting in the complete removal of the diseased nucleoside from the DNA. Subsequently, it rearranges to a Schiff base. Consequently, FPG also has a nick at the purine/pyrimidine (AP) site, resulting in a gap in the DNA that contains phosphate groups at both the 5' and 3' extremities.