Ligase

A Ligase is an enzyme that can ligate[?] ("glue together") two molecules with a covalent bond, using energy from ATP.

DNA ligase can ligate broken DNA strands, forming covalent phosphodiester bonds.

An example of how a ligase works (with sticky ends):

 5'-AGTCTGATCTGACT        GATGCGTATGCTAGTGCT-3'
 3'-TCAGACTAGACTGACTACG        CATACGATCACGA-5'
 becomes
 5'-AGTCTGATCTGACTGATGCGTATGCTAGTGCT-3'
 3'-TCAGACTAGACTGACTACGCATACGATCACGA-5'