Enzymes: The Active Site

Abstract Enzymes are highly efficient and specific catalysts. They catalyse biochemical reactions with substantial rate enhancement compared to the uncatalysed reactions. The rate enhancement and specificity of enzymes are derived from a network of general acid/base catalysts, nucleophiles and noncovalent interactions in the active site, the part of the enzyme where cataylsis takes place. In catalysis, binding of the substrate and the transition state in the active site is of critical importance. Enzymes catalyse reactions by preferentially binding the transition state and, therefore, lowering the activation energy of the reaction. Enzymes bind their substrates via a network of weak, noncovalent intermolecular interactions such as hydrogen bonding, hydrophobic and electrostatic interactions. Enzymes utilise several mechanisms to accelerate a reaction such as acid/base catalysis, covalent catalysis and metal ion catalysis. Owing to their integral role in all biochemical pathways, enzymes are an attractive target for drug design and development. Key Concepts: Enzymes are biocatalysts that are involved in all forms of biochemical transformations. Nearly all enzymes are proteins. Enzymes catalyse reactions with a remarkable rate enhancement due primarily to lowering the energy of the transition state. The active site is a cavity in the enzyme structure where catalysis occurs. Amino acid residues in the active site provide the required framework for catalysis.