Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts. They are responsible for thousands of metabolic processes that sustain life.
Enzymes are highly selective catalysts, both greatly accelerating the rate and greatly enhancing the specificity of metabolic chemical reactions, from the digestion of food to the synthesis of DNA. Most enzymes are proteins, although some catalytic RNA molecules have been identified. Enzymes adopt a specific three-dimensional structure, and may employ organic (e.g. biotin) and inorganic (e.g. magnesium ion) cofactors to assist in catalysis.