Chemical Properties
This off-white lyophilized powder is freely soluble in water and slightly soluble in 30% ethanol and acetone, with an optimal pH of 7.8. Adding 5 mmol/L Ca2+ or diisopropylfluorophosphate (DFP) to the aqueous solution can increase its stability. Inhibitors include EDTA and sodium dodecyl sulfate; activators are divalent metal ions; the combination of Mg2+ and Ca2+ yields the best results. The absorption coefficient of a 1% aqueous solution at 280 nm is 11.1. The average chain length in restriction digestion is four nucleotides. The enzyme reaction: deoxyribonucleic acid = dinucleotide-5'-phosphate + oligonucleotide-5'-phosphate.
Uses
Deoxyribonuclease I is used for the removal of DNA from protein samples. DNAse I is used to nick DNA as a first step to incorporate labeled bases into DNA. The enzyme from Sigma has been used during the isolation of plasma membrane vesicles from Neurospora crassa cell culture.1 It has also been used along with trypsin for the preparation of single cell suspension from rat testes. Deoxyribonuclease I from bovine pancreas has been used in a study to compare several procedures for reducing RNase contamination in preparations of DNase. Deoxyribonuclease I from bovine pancreas has also been used in a study to investigate the effect of the composition of sodium dodecyl sulfate preparations on the renaturation of enzymes after polyacrylamide gel electrophoresis
General Description
DNase I, or Deoxyribonuclease I, is an endonuclease isolated from bovine pancreas.
- Our DNase I Digests double str and single stranded DNA into oligo and mononucleotides.
- Bovine pancreatic DNase exists as four isozymes, having isoelectric points for A, B, C and D: 5.22, 4.96, 5.06 and 4.78.3. The predominant form is A, with smaller amounts of B and C, and only minor amount of D.
- DNase I structure resembles the structure of to exonuclease III. It includes two central ? sheets. Each β sheet is composed of six β-strands. This complex of β sheets is surrounded by extensive loop and α-helical regions. This enzyme shares structural similarity to exonuclease III.[1]
Flammability and Explosibility
Notclassified
Biochem/physiol Actions
DNase I is an endonuclease that acts on phosphodiester bonds adjacent to pyrimidines to produce polynucleotides with terminal 5′-phosphates. In the presence of Mg2+, DNAse I cleaves each strand of DNA independently and the cleavage sites are random. Both DNA strands are cleaved at approximately the same site in the presence of Mn2+. The pH optimum is found to be between 7 and 8. Divalent cations such as Mn2+, Ca2+, Co2+, and Zn2+ are activators of the enzyme. A concentration of 5 mM Ca2+ stabilizes the enzyme against proteolytic digestion. DNAse I from bovine pancreas consists of four chromatographically distinguishable components, A, B, C, and D, with their molar ratios being 4:1:1. Only minor amounts of D are found. 2-Mercaptoethanol, chelators, sodium dodecyl sulfate (SDS) and actin are known to inhibit the enzyme activity.
Clinical Use
DNAse is a human endonuclease, normally present insaliva, urine, pancreatic secretions, and blood. The enzymecatalyzes the hydrolysis of extracellular DNA into oligonucleotides.Aerosolized recombinant human deoxyribonucleaseI (rhDNAse), dornase alfa, Pulmozyme, has beenformulated into an inhalation agent for the treatment of pulmonarydisease in patients with CF.Among the clinical manifestations of CF are obstructionof the airways by viscous, dehydrated mucus. Pulmonaryfunction is diminished, and microbes can become entrappedin the viscid matrix. A cycle of pulmonary obstruction andinfection leads to progressive lung destruction and eventualdeath before the age of 30 for most CF patients. The immunesystem responds by sending in neutrophils, and theseaccumulate and eventually degenerate, releasing largeamounts of DNA. The high levels of extracellular DNA releasedand the mucous glycoproteins are responsible for thedegenerating lung function. The DNA-rich secretions alsobind to aminoglycoside antibiotics typically used to treat theinfections. In vitro studies showed that the viscosity of thesecretions could be reduced by application of DNAse I.
Pulmozyme is approved for use in the treatment of CFpatients, in conjunction with standard therapies, to reducethe frequency of respiratory infections requiring parenteralantibiotics and to improve pulmonary function. The dose isdelivered at a level of 2.5 mg daily with a nebulizer.Pulmozyme is not a replacement for antibiotics, bronchodilators,and daily physical therapy.
