Nukleasi

Nukleasi, or nucleases in English, are enzymes that catalyze the cleavage of nucleic acids such as DNA and RNA. They play essential roles in cellular processes including DNA repair, replication, RNA processing, and programmed cell death, and they are also central tools in molecular biology. Nukleasi can be classified by their substrate into deoxyribonucleases (DNases) and ribonucleases (RNases), and by mechanism as endonukleases, which cut within a nucleic acid strand, and exonukleases, which remove nucleotides from the ends of a molecule.

Cofactors and specificity: Many nucleases require divalent metal ions such as Mg2+ or Mn2+ to activate a water molecule for phosphodiester bond hydrolysis; others operate without metal cofactors. DNases and RNases differ in nucleic acid targets, while some nucleases, such as restriction endonucleases, recognize specific DNA sequences, whereas nonspecific nucleases act broadly.

Notable examples and applications: Examples include DNase I and DNase II (DNA-cleaving), RNase A and RNase H (RNA-cleaving). Restriction enzymes, a class of sequence-specific endonucleases, enable cloning and DNA mapping, while CRISPR-associated nucleases like Cas9 and Cas12 are used for genome editing. In research and diagnostics, nucleases are used to remove unwanted nucleic acids, to digest nucleic acids during purification, and to analyze sequence composition.

Safety and handling: Nucleases are often highly active and must be controlled to protect nucleic acids; RNases are particularly pervasive and require careful laboratory practice to prevent contamination.