Enzymes: The Biological Synthesis Of Protein

Enzymes are homogeneous biological catalyst that work by lowering the activation of a reaction pathway or providing a new pathway with a low activation energy. Enzymes are special biological polymers that contain an active site, which is responsible for binding the substrates, the reactants, and processing them into products. As is true of any catalyst, the active site returns to its original state after the products are released. Many enzymes consist primarily of proteins, some featuring organic or inorganic cofactors in their active sites. However, certain ribonucleic acid (RNA) molecules can also be biological catalysts, forming ribozymes. A very important example of a ribozyme is the ribosome, a large assembly of proteins and catalytically active RNA molecules responsible for the synthesis of proteins in the cell. The structure of the active site is specific to the reaction that it catalyzes, with groups in the substrate

Koshland proposed induced fit hypothesis in 1959. The active sites of these enzymes have shapes that are complementary to that of the substrate only after the substrate is bound. Such enzyme-substrate interaction are described by induced fit model. The advantages of the induced fit mechanism arise due to the stabilizing effect of strong enzyme binding. There are two different mechanisms of substrate binding: uniform binding, which has strong substrate binding, and differential binding, which has strong transition state binding. The stabilizing effect of uniform binding increases both substrate and transition state binding affinity, while differential binding increases only transition state binding affinity. Most proteins seem to use the differential binding mechanism to reduce the Ea, so most proteins have high affinity of the enzyme to the transition state. The substrate first binds weakly, then the enzyme changes conformation increasing the affinity to the transition state and stabilizing it, so reducing the activation energy to reach