DNA-hydrolyzing enzyme

Patients with cystic fibrosis use aerosol inhaler sprays of the DNA-hydrolyzing enzyme deoxyribonuclease to help reduce the viscosity of mucous secretions, which contain large amounts of DMA arising from destruction of WBCs as they fight lung Infections. 

Avery and his colleagues concluded that the DNA extracted from the virulent strain carried the inheritable genetic message for virulence. Not everyone accepted these conclusions, because protein impurities present in the DNA could have been the carrier of the genetic information. This possibility was soon elimtnated by the finding that treatment of the DNA with proteolytic enzymes did not destroy the transforming activity, but treatment with deoxyribonucleases (DNA-hydrolyzing enzymes) did. 

Staphylococcal nuclease, a DNA-hydrolyzing enzyme, is a single polypeptide chain of 149 amino acid residues it has no disulfide bridge and contains one Ca ion. This protein was originally isolated from Staphylococcus aureus, but the gene has been cloned and inserted into several expression systems. Various mutants of this enzyme have been used to generate biochemical and biophysical data on the structural and functional consequences of altering the protein amino acid sequence. 

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