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+
Divalent cations such as Mn2+
, and Zn2+
are activators of the enzyme. A concentration of 5 mM Ca2+
stabilizes the enzyme against proteolytic digestion. The pH optimum is found to be between 7 and 8.
DNAse I from bovine pancreas consists of four chromatographically distinguishable components, A, B, C, and D, with their molar ratios being 4:1:1 respectively. Only minor amounts of D are found.
2-Mercaptoethanol, chelators, sodium dodecyl sulfate (SDS)
are known to inhibit the enzyme activity.