Endonuclease of the viral base excision repair system that catalyzes DNA cleavage reaction at the apurinic or apyrimidinic sites (AP sites) (By similarity). Cleaves phosphodiester bonds on the 5' side of AP sites (By similarity). In addition to endonuclease activity, the AP endonuclease has a proofreading 3'-5' exonuclease activity that is considerably more efficient in the elimination of a mismatch than in that of a correctly paired base (By similarity). Displays 3'-phosphatase and 3'-repair diesterase activities (By similarity). The single nucleotide gaps generated by the AP endonuclease are filled by the viral repair DNA polymerase X and the DNA ligase (Probable). Binds 3 Zn(2+) ions. The early enzyme is localized in the nucleus and the cytoplasm, while the late protein is found only in the cytoplasm (By similarity). Found in association with viral nucleoid (By similarity). Expressed in the early phase of the viral replicative cycle and accumulates at later times. Consistent with its intracellular location, ASFV encodes its own replicative DNA polymerase and three base excision repair enzymes: a class II AP endonuclease, the repair polymerase Pol X, and an ATP-dependent DNA ligase. Belongs to the AP endonuclease 2 family.