An enzyme is a biological macromolecule that accelerates — or catalyzes — chemical reactions within cells and organisms. Enzymes aren’t consumed in the reaction, and they can even work under conditions that would otherwise be impossible. They’re incredibly important to the complex processes that keep living things working.
Enzymes are always proteins, which means they’re large molecules made of repeating molecular subunits called monomers. Most large biological molecules are polymers, long chains of monomers strung together, much like a necklace with beads. Enzymes are made by the body in a process called protein synthesis, where the genetic information encoded in DNA is transcribed into RNA and then translated into a sequence of amino acids that makes up an enzyme.
Each enzyme has a specific shape that defines its “active site.” The active site is the area of the enzyme where it binds to another molecule, the substrate. The match between the active site and substrate is highly precise — a kind of lock-and-key fit — allowing the enzyme to precisely perform its catalytic role.
The overall three-dimensional structure of an enzyme is determined by its secondary, tertiary, and quaternary structures, which describe localized patterns of folding of polypeptide chain segments, such as alpha-helices or beta-sheets. These are stabilized by interactions between amino acid side chains, and are essential for an enzyme’s specific chemistry.
Some metal ions, such as zinc, iron, and copper, also act as cofactors to assist an enzyme in carrying out its catalytic function. Other types of cofactors include vitamins, sugars, and lipids.