5'-3' exonuclease that plays a central role in telomere maintenance and protection during S-phase. Participates in the protection of telomeres against non-homologous end-joining (NHEJ)-mediated repair, thereby ensuring that telomeres do not fuse. Plays a key role in telomeric loop (T loop) formation by being recruited by terf2 at the leading end telomeres and by processing leading-end telomeres immediately after their replication via its exonuclease activity: generates 3' single-stranded overhang at the leading end telomeres avoiding blunt leading-end telomeres that are vulnerable to end-joining reactions and expose the telomere end in a manner that activates the DNA repair pathways (By similarity). Possesses beta-lactamase activity, catalyzing the hydrolysis of penicillin G and nitrocefin (By similarity). Exhibits no activity towards other beta-lactam antibiotic classes including cephalosporins (cefotaxime) and carbapenems (imipenem) (By similarity). a beta-lactam + H2O = a substituted beta-amino acid Interacts with terf2; the interaction is direct. The TBM domain mediates interaction with terf2. Belongs to the DNA repair metallo-beta-lactamase (DRMBL) family.