Enzymes are primarily composed of proteins, and the building blocks of proteins are amino acids. There are 20 different amino acids that combine in various sequences to form proteins, including enzymes. Each enzyme has a unique structure and function, determined by the specific order of amino acids in its chain.
Amino acids are linked together by peptide bonds, forming long chains that fold into specific three-dimensional shapes. This folding is critical because the shape of an enzyme determines its activity and how it interacts with substrates (the molecules upon which enzymes act). Additionally, some enzymes may require non-protein molecules called cofactors or coenzymes to function properly, but the core building blocks are always amino acids.