Lyases

the class of enzymes that catalyze the nonhydrolytic splitting of certain groups from their substrates, involving the formation of double bonds. Lyases also catalyze the reverse reaction: the joining of groups by double bonds. Lyases are classified as carbon-carbon lyases (some of these are called synthases), carbon-nitrogen, carbon-oxygen, and so forth. Unlike ligases, lyases bring about synthase reactions without the participation of energy-rich (macroergic) compounds.