Allosteric regulation is the major mechanism by which enzymes are controlled in cells. Since enzymes perform virtually every function in a cell, their regulation is a vital part of cell biochemistry.

Enzymes are highly specific catalysts for cell reactions. They promote reactions by binding to reactants, called substrates, at a cleft in their surface called the active site. When substrate binds to the active site, it is transformed into the product, which then detaches to open the site for new substrates.

In order to control the rate of the catalyzed reaction, the cell must have a way to turn the enzyme on and off as needed. This can either be accomplished by blocking the active site directly, or by inducing a change in the enzyme's shape (called a conformation change) that alters the shape of the active site. Enzymes that undergo such shape changes are called...