The function of TATDN1 (TatD DNase domain containing 1, ENSG00000147687) is as follows. Exhibits 3'-5' exonuclease and apurinic/apyrimidinic (AP) endonuclease activities (in vitro) (PubMed:36881763). Shows preferential AP endonuclease activity on dsDNA substrates and 3'-5' exonuclease activity on ssDNA (PubMed:36881763). Catalyzes decatenation of catenated kinetoplast DNA to produce separated linear DNA in vitro (By similarity). Plays an important role in chromosomal segregation and cell cycle progression during eye development probably via its DNA decatenation activity (By similarity). {ECO:0000250|UniProtKB:Q6GML7, ECO:0000269|PubMed:36881763}.