Purification and properties of deoxyribonucleic acid ligases from rat liver

DNA ligases have been purified 1,500-fold cytoplasmic fraction and 114-fold from 0.15 M NaCl extract of rat-liver nuclei. These enzymes catalyze the formation of a phosphodiester linkage between the 3'-hydroxyl group and the 5'-phosphoryl group of an interrupted strand in a DNA duplex. The enzyme from each fraction requires ATP and Mg2+ (or Mn2+) for activity, and its inhibited reversibly by p-chloromercuribenzoate. The cytoplasmic and nuclear enzymes are distinguished from each other by the following criteria: apparent molecular weight; sedimentation coefficient; charge properties; Km for Mg2+ (or Mn2+); Km for ATP; effect of ionic strength on the molecular and kinetic properties.