| Type: | Active_site | Name: | Deoxyribonuclease I, active site |
| Description: | Deoxyribonuclease I (DNase I) () [] is a vertebrate enzyme which catalyzes the endonucleolytic cleavage of double-stranded DNA to 5'- phosphodinucleotide and 5'-phosphooligonucleotide end-products. DNase I is an enzyme involved in DNA degradation; it is normally secreted outside of the cell but seems to be able to gain access to the nucleus where it is involved in cell death by apoptosis [].As shown in the following schematic representation, DNase I is a glycoprotein of about 260 residues with two conserved disulphide bonds. +-+ +--------+ | | | |xxxxxxxxxxxxxxxxx#xxxxxxCxCxxxxx#xxxxxxxxxCxxxxxxxxCxxxxxxxxxxxxx 'C': conserved cysteine involved in a disulphide bond.'#': active site residue. DNase I has a pH-optimum around 7.5 and requires calcium and magnesium for full activity. It causes single strand nicks in duplex DNA. A proton acceptor-donor chain composed of an histidine and a glutamic acid produce a nucleophilic hydroxyl ion from water, which cleaves the 3'-P-O bond [].DNase I forms a 1:1 complex with G-actin, resulting in the inhibition of DNase activity and loss of the ability of G-actin to polymerise into fibres [].DNase I has been used in the treatment of lung problems in patients with cystic fibrosis: here it acts by degrading DNA found in purulent lung secretions, reducing their viscosity and making it easier for the patient to breathe [].The sequence of DNase I is evolutionary related to that of human muscle-specific DNase-like protein and human proteins DHP1 and DHP2. However, the first disulphide bond of DNase I is not conserved in these proteins.This entry represents two conserved patterns, with DNASE_I_1 containing the conserved active site histidine residue []. | Short Name: | Deoxyribonuclease-1_AS |
