nucleasas

Nucleases are enzymes that cleave nucleic acids by hydrolyzing phosphodiester bonds. They act on DNA, RNA, or both, and play essential roles in nucleic acid metabolism, repair, replication, recombination, and turnover. Nucleases are commonly classified by where they act on the substrate: endonucleases cut within a nucleic acid chain, while exonucleases remove nucleotides from the ends.

Endonucleases include restriction enzymes that recognize specific DNA sequences and generate defined fragments. Other endonucleases, such as DNase I and RNase A, act non-specifically to cleave DNA or RNA, respectively. Exonucleases remove nucleotides from 5' or 3' ends, and can be directionally specific. Some nucleases target only RNA (RNases), while others target DNA (DNases), and a subset, such as CRISPR-associated nucleases, function as programmable endonucleases guided by RNA.

Mechanistically, many nucleases require divalent metal ions (commonly Mg2+ or Mn2+) to catalyze phosphodiester bond cleavage, often via a two-metal-ion mechanism. Others are metal-independent and rely on specific catalytic residues. Structural families of nucleases include metallo-β-lactamase-like enzymes, RNase A-like enzymes with histidine-based catalysis, and programmable nucleases such as the CRISPR–Cas systems (e.g., Cas9, Cas12) that introduce targeted double-strand breaks.

Biological roles include processing and turnover of nucleic acids, participation in DNA repair and recombination, apoptosis, and defense against foreign genetic material. In laboratory settings, nuclease activity is tightly controlled due to the instability of nucleic acids; RNases in particular require strict RNase-free techniques to protect RNA samples.

Applications span biotechnology and medicine, including DNA cloning and sequencing with restriction enzymes, genome editing with Cas nucleases, and techniques for removing DNA from RNA preparations or studying RNA turnover.