Properties of Deoxyribonuclease III from Mammalian Tissues

Abstract

A DNA exonuclease, DNase III, has been purified 680-fold from normal rabbit bone marrow. The enzyme has a pH optimum at 8.5, requires Mg++ or Mn++ as a cofactor, and has a molecular weight of 52,000 ± 5,000. It hydrolyzes denatured DNA four times more rapidly than native DNA with no apparent base specificity, but it does not attack RNA. DNA is degraded from the 3′ end with the release of 5′-mononucleotides and dinucleotides. DNase III is localized in the cell nucleus, and it appears to be the predominant DNA exonuclease in many different mammalian tissues.