Ligase

In biochemistry, ligase (from the Latin verb ligāre — "to bind" or "to glue together") is an enzyme that can catalyze the joining of two large molecules by forming a new chemical bond, usually with accompanying hydrolysis of a small chemical group dependent to one of the larger molecules or the enzyme catalyzing the linking together of two compounds....e.g.: Enzymes which catalyze joining of C-O,C-S,C-N etc. .In general, a ligase catalyzes the following reaction:

Ab + C → A–C + b

or sometimes

Ab + cD → A–D + b + c

where the lowercase letters signify the small, dependent groups.