DNases

DNases are enzymes that hydrolyze DNA, contributing to DNA turnover, remodeling, and defense in a variety of organisms. The two best characterized families are DNase I and DNase II. DNase I enzymes are typically secreted or extracellular and function best at near-neutral pH in the presence of divalent cations such as calcium and magnesium. They cleave DNA endonucleolytically, producing fragments with 5' phosphate and 3' hydroxyl ends. DNase II enzymes are lysosomal nucleases that operate at acidic pH and do not require metal ions; they digest DNA within lysosomes and phagosomes.

Biological roles of DNases include participation in apoptosis, where nucleases fragment genomic DNA, and in the turnover of extracellular DNA, such as the degradation of neutrophil extracellular traps. Some bacteria secrete DNases that aid in immune evasion by dismantling DNA-based traps. In higher organisms, DNases contribute to DNA recycling and to processing material internalized by phagocytes.

In molecular biology, DNase I treatment is used to remove contaminating DNA from RNA preparations and to prevent carryover PCR amplification. Clinically, recombinant DNase I (dornase alfa) is used to reduce mucus viscosity in cystic fibrosis and other pulmonary diseases by degrading extracellular DNA in mucus.

Regulation and inhibitors of DNases include chelating agents such as EDTA, which sequester calcium and magnesium and inhibit DNase I activity. Actin can bind DNase I and inhibit its function. DNases are widespread, found in bacteria, fungi, plants, and animals, and may be secreted, lysosomal, or cytosolic depending on the enzyme.