Practice question

Deoxyribonuclease I is an endonuclease that hydrolyzes internal phosphodiester bonds rather than removing nucleotides from termini. Isolated from bovine pancreas, it is a 31 kilodalton glycoprotein requiring divalent cations, specifically calcium for stability and magnesium for catalytic activity, yielding fragments with 5'-phosphate and 3'-hydroxyl ends. It degrades double-stranded DNA, with slower activity on single-stranded DNA and chromatin. Limiting enzyme concentration generates single-strand nicks useful for nick translation labeling, while higher concentrations produce double-strand breaks. Its endonucleolytic mechanism contrasts with exonucleases acting from ends.