DNA ligase
DNA li·gase (liґgās) an enzyme of the ligase class that catalyzes the energy-driven linkage of a double-stranded DNA chain with a free 3′ hydroxyl group to one with a 5′ phosphate group, forming a phosphodiester bond between them. The reaction is important in the repair of damaged DNA and in the joining of Okazaki fragments during DNA replication. In animals and bacteriophages, the enzyme uses ATP as an energy source and is officially called DNA ligase (ATP) [EC 6.5.1.1]. In bacteria, it uses NAD as the energy source and the enzyme is officially called DNA ligase (NAD) [EC 6.5.1.2]. Both are used in vitro in the formation of recombinant molecules.
Medical dictionary.
2011.