Functions as a apurinic/apyrimidinic (AP) endodeoxyribonuclease in the DNA base excision repair (BER) pathway of DNA lesions induced by oxidative and alkylating agents. Initiates repair of AP sites in DNA by catalyzing hydrolytic incision of the phosphodiester backbone immediately adjacent to the damage, generating a single-strand break with 5'-deoxyribose phosphate and 3'-hydroxyl ends. May also play a role in the epigenetic regulation of gene expression by participating in DNA demethylation. Required for passage through the midblastula transition MBT. May also act as an endoribonuclease involved in the control of single-stranded RNA metabolism. Has no redox activity. Binds DNA and RNA. Exonucleolytic cleavage in the 3'- to 5'-direction to yield nucleoside 5'-phosphates. Probably binds two magnesium or manganese ions per subunit. Expressed in unfertilized eggs and embryos at two stages (at protein level). Expressed throughout embryogenesis. Belongs to the DNA repair enzymes AP/ExoA family.