Lyasen

Lyasen, in English more commonly referred to as lyases, is a class of enzymes that catalyze the breaking and forming of chemical bonds by mechanisms other than hydrolysis or oxidation. The reactions typically involve the cleavage of carbon–carbon, carbon–oxygen, carbon–nitrogen, or carbon–sulfur bonds, or the making of new double bonds through elimination, addition, or rearrangement steps. Lyases often promote the formation of pi bonds or rings and can operate in an irreversible or reversible fashion depending on the reaction.

In common biochemical nomenclature, lyases are grouped into several subcategories by the type of bond acted on and the reaction produced. Prominent examples include decarboxylases that remove CO2 from substrates and aldolases that cleave carbon–carbon bonds to form carbonyl compounds; hydratases and related lyases that add water or other groups across double bonds; and synthases that create new bonds without relying on ATP hydrolysis. Many lyases require cofactors such as pyridoxal phosphate, thiamine pyrophosphate, or metal ions to stabilize reaction intermediates.

Lyases are widely distributed across bacteria, archaea, and eukaryotes and play essential roles in metabolism, including amino acid and carbohydrate pathways. The term lyase derives from the Greek lysis, meaning to loosen or split; the enzymes are classified as EC class 4 in the enzyme commission system.