ligases (synthetases)

Enzymes that catalyse the ligation of two molecules with concomitant hydrolysis of the pyrophosphate bond in adenosine 5'-triphosphate (ATP) or a similar triphosphate, forming C–C , C–O , C–S , P–O or C–N bonds. In recombinant DNA technology, ligases covalently join together two sequences of DNA (e.g. hostDNA and foreign DNA) by a phosphodiester bond.
Source:
PAC, 1992, 64, 143 (Glossary for chemists of terms used in biotechnology (IUPAC Recommendations 1992)) on page 159