DNA repair enzyme that cleaves apurinic/apyrimidinic (AP) sites and removes 3'-blocking groups present at single strand breaks of damaged DNA. Exonucleolytic cleavage in the 3'- to 5'-direction to yield nucleoside 5'-phosphates. Probably binds two magnesium or manganese ions per subunit. Present with 414 molecules/cell in log phase SD medium. Belongs to the DNA repair enzymes AP/ExoA family.