DNase I is an endonuclease that acts on phosphodiester bonds adjacent to pyrimidines to produce polynucleotides with terminal 5′-phosphates. The pH optimum is found to be between 7 and 8. Divalent cations such as Mn2+
, and Zn2+
are activators of the enzyme. A concentration of 5 mM Ca2+
stabilizes the enzyme against proteolytic digestion.
2-Mercaptoethanol, chelators, sodium dodecyl sulfate (SDS)
are known to inhibit the enzyme activity.
Digests single- and double-stranded DNA to a mixture of mono- and oligonucleotides carrying 5′ phosphates and 3′ OH termini. This catalytic activity is divalent ion-dependent. In the presence of Mg2+, DNase I hydrolyzes each strand of double-stranded DNA randomly and independently. In the presence of Mn2+, both strands can be cleaved.