Exodeoxyribonuclease from rat brain specific for single-stranded DNA.

An exodeoxynuclease with single-stranded DNA specificity has been isolated from rat brain and purified to electrophoretic homogeneity. Approximately 1100-fold purification with a yield of 16% has been achieved by chromatography on DNA-agarose, hydroxyapatite and Sephadex G-200. The enzyme has a pH optimum at 8.4, requires Mg2+ or Mn2+ as a cofactor and has a molecular weight of about 60000. It hydrolyzes homologous, heterologous, synthetic and depurinated substrates at the same rate liberating nucleoside 5'-monophosphates but does not attack ultraviolet-irradiated polydeoxyribonucleotides. This DNase is localized predominantly in neuronal cell nuclei and appears to be lacking in rat liver tissue.