Polyamine-dependent deoxyribonuclease activity from rat-liver nuclei.

When nuclei isolated from rat liver in a low salt buffer were washed with 0.1 M NaCl solution, the supernatant showed a deoxyribonuclease (DNase) activity. The activity required Mg2+ and in addition spermine or spermidine, and its optimal pH was 7.2-7.4. The activity was higher on denatured (single stranded) DNA than on double-helical DNA. With both substrates the activity was highest at a polyamine concentration at which the DNA-polyamine complex began to precipitate. No Mg2++Ca2+ dependent DNase activity was detected in the preparation.