Deoxyribonuclease from beef pancreas, DNase I, was first crystallized by Kunitz. It is an endonuclease which splits phosphodiester linkages, preferentially adjacent to a pyrimidine nucleotide yielding 5'-phosphate terminated polynucleotides with a free hydroxyl group on position 3'. The average chain of limit digest is a tetranucleotide. DNase I acts upon single chain DNA, and upon double-stranded DNA and chromatin. In the latter case, although histones restrict susceptibility to nuclease action, over a period of time nearly all chromatin DNA is acted upon. According to Mirsky and Silverman, this could result from the looseness of histone attachment to DNA. They found that lysine-rich histones more effectively block DNase access to DNA than arginine-rich histones. Billing and Bonner suggest that DNase attacks the histone-free strand of chromatin DNA. Schmidt, et. al.indicate that hydrolysis of the histone-free region of DNA strands accounts for the initial rapid action of the enzyme on chromatin. Bollum reports degradation of synthetic homopolymer complexes by DNase I. The intracellular functions of the enzyme are probably controlled by a DNase inhibitor, which according to Lazarides and Lindberg is actin.
DNase I is used as a genetic marker for forensic identification. Used for the removal of DNA from protein samples. 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.
Pancreatic deoxyribonuclease is unusually sensitive to physical denaturation by shaking. Mixing should be done by gentle inversion. Dissolve the standard in 1.0 mL of reagent grade water. Dilute further to a concentration of 20-60 u/mL. All dilutions are made in reagent grade water.
Amount of enzyme that causes the fall of 1.0 relative viscosity unit in a solution of highly polymerized DNA in 10 minutes at 30°C from the intial relative viscosity of 4.0.
Specific Activity: >50,000 Dornase u/mg solid
Key Applications: Marker, Cell lysis, Enzymes, Inhibitors, Substrates
Application Areas: Molecular biology, Cell biology
Product Type: Proteins, Enzymes & Peptides
Extinction Coefficient (E1%): 11.1 at 280 (Lit.)
Presentation: White powder
Format: Powder
pH: Optimum pH: 7.8(Lit.)
NOTES:
Activators: DNase I is activated by bivalent metals. Maximum activation is attained with Mg2+ plus Ca2+. It has been indicated that a metallosubstrate, such as Mg salt of DNA might be necessary.
Inhibitors: According to Davidson, citrate completely inhibits magnesium-activated but not manganese-activated enzyme. DNase I is inhibited by chelating agents such as EDTA and sodium dodecyl sulfate.
Stabilizers: The most likely proteolytic contaminant of DNase I is chymotrypsin B. Price, et. al. report that DNase I can be stabilized against proteolytic digestion by 5 mM Ca2+. Di-isopropylfluorophosphate (DFP) may also be used to inhibit contaminating proteases.
Storage & Handling: Store at -0°C.