Ligases

Ligases (EC class 6) are enzymes that join two molecules together with the formation of a new bond — powered by hydrolysis of the pyrophosphate bond in ATP or a similar nucleoside triphosphate. Important in synthesising and repairing biological molecules such as DNA (DNA ligase seals nicks in the backbone) and in joining amino acids to tRNA, they are subdivided by the bonds they form: carbon–oxygen, carbon–sulfur, carbon–nitrogen, carbon–carbon and phosphoric-ester bonds. In food biotechnology they are workhorse molecular-biology tools — DNA ligases assemble plasmids and constructs for strain engineering — and acetyl-CoA carboxylase (a ligase) initiates fatty-acid synthesis relevant to oilseed composition.