53Exonuklease

53Exonuklease is a DNA exonuclease enzyme with 5' to 3' exonuclease activity. It degrades nucleotides from the 5' end of DNA substrates, acting on single-stranded DNA and on nicked double-stranded DNA under suitable conditions. The enzyme is defined by its directional specificity and its requirement for metal ions in catalysis.

Biochemical properties indicate that catalysis relies on divalent metal ions such as Mg2+ or Mn2+. It follows a two-metal-ion mechanism common to many nucleases, with an active site featuring conserved acidic residues that coordinate metals and activate a water molecule for nucleophilic attack on the phosphodiester backbone.

Substrate preference and regulation show that 53Exonuklease has higher efficiency on DNA ends bearing a 5' phosphate and can act on nicked or partially unwound DNA. Its activity is influenced by ionic strength, pH, and interactions with accessory proteins that modulate access to DNA ends.

Biological role in cells includes participation in DNA end processing during replication, repair, and recombination. By removing mispaired or damaged nucleotides from the 5' end, it contributes to end maturation prior to ligation or gap filling, and it may operate in concert with helicases and other nucleases as part of a broader DNA repair network.

Applications and research note that 53Exonuklease is used in laboratory settings to generate defined DNA ends for cloning, sequencing libraries, or end-repair assays. Ongoing studies investigate its physiological substrates, regulation, and potential as a target for antimicrobial or anticancer strategies.