Endonuclease of the viral base excision repair system that catalyzes DNA cleavage reaction at the apurinic or apyrimidinic sites (AP sites) (PubMed:16503634, PubMed:16641276). Cleaves phosphodiester bonds on the 5' side of AP sites (PubMed:16503634). 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 (PubMed:16641276). Displays 3'-phosphatase and 3'-repair diesterase activities (PubMed:16503634). 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 (PubMed:16641276). Found in association with viral nucleoid (PubMed:30185597). Expressed in the early phase of the viral replicative cycle and accumulates at later times. Decreases the growth rate of the virus to 2-4% of the parental virus in swine macrophages. 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.