GLOSSARY: Active Site

Active Site is defined as a part of an enzyme where substrates bind and undergo a chemical reaction. The majority of enzymes are proteins but RNA enzymes called ribozymes also exist. The active site of an enzyme is usually found in a cleft or pocket that is lined by amino acid residues (or nucleotides in ribozymes) that participates in recognition of the substrate. Residues that directly participate in the catalytic reaction mechanism are called active site residues.