GO:0140078:   class I DNA-(apurinic or apyrimidinic site) endonuclease activity
Catalysis of the cleavage of an AP site 3" of the baseless site by a beta-lyase mechanism, leaving an unsaturated aldehyde, termed a 3"-(4-hydroxy-5-phospho-2-pentenal) residue, and a 5"-phosphate.