Dnase

Deoxyribonuclease (DNase) is a group of enzymes that catalyze the cleavage of DNA, breaking the phosphodiester bonds that link the nucleotides. DNase plays a crucial role in various biological processes, including DNA repair, recombination, and apoptosis. There are two main types of DNase: DNase I and DNase II, each with distinct properties and functions.

Types of DNase

DNase I

DNase I (EC 3.1.21.1) is an endonuclease that cleaves DNA preferentially at phosphodiester linkages adjacent to a pyrimidine nucleotide, yielding 5'-phosphate-terminated oligonucleotides with a free hydroxyl group at the 3' position. It is commonly found in various tissues and bodily fluids. DNase I is extensively used in molecular biology for removing DNA from RNA preparations and for nicking DNA in footprinting assays.

DNase II

DNase II (EC 3.1.22.1) is an endonuclease that cleaves DNA to oligonucleotides containing a free 3' hydroxyl and a phosphate group at the 5' position. Unlike DNase I, DNase II does not require divalent cations for its activity and functions in acidic conditions. It plays a significant role in the degradation of DNA during apoptosis and is involved in the immune system's response to infection.

Functions and Applications

DNase enzymes have a wide range of functions and applications in both physiological processes and biotechnological practices.

Biological Functions

In biological systems, DNases are involved in the maintenance of genomic integrity through the repair of damaged DNA, the facilitation of recombination events necessary for genetic diversity, and the degradation of DNA during apoptosis, ensuring the orderly disposal of cellular components.

Biotechnological Applications

In biotechnology and molecular biology, DNases are used to remove DNA contamination from RNA samples, a critical step in the preparation of samples for RNA-based techniques such as reverse transcription polymerase chain reaction (RT-PCR). DNase I, in particular, is used to nick DNA in footprinting assays to study protein-DNA interactions. Additionally, DNase is employed in the treatment of cystic fibrosis to reduce the viscosity of mucus, improving the patients' respiratory function.

Clinical Significance

The therapeutic application of DNase, especially recombinant human DNase I (rhDNase), has been a significant advancement in the treatment of cystic fibrosis. By cleaving extracellular DNA in the thick mucus secretions characteristic of the disease, rhDNase helps to decrease viscosity and improve lung function. This treatment has become a standard part of managing cystic fibrosis, highlighting the importance of DNase in medicine.

See Also

• Enzyme
• DNA
• Cystic Fibrosis
• Molecular Biology