Enzymes are protein molecules that speed up chemical reactions in the cell. A special region on the enzyme, called the active site, is the area where enzyme activity takes place. An enzyme works by binding to molecules, called substrates, at its active site.
The job of the enzyme is to convert the substrate into a different product or products through a series of chemical reactions. Following the reactions, the products are released and the enzyme is free to act on another substrate. At the active site, the substrate should fit into the enzyme almost like a key fits into a lock. Because of this, most enzymes can fit only one substrate. To accomplish this lock and key fit, the active site undergoes a slight change in shape in order to better accommodate the substrate.
This is called the induced fit model because the enzyme is induced to undergo small changes so that the substrate can achieve optimum fit. All enzymes have optimal environmental conditions that are correlated with maximum enzyme activity. Environmental conditions such as pH and temperature play a role in how efficient the enzyme is in conducting its reactions.
When conditions are less than optimal, An enzyme will lose its configuration and slow its activity. This is due to a change in the three-dimensional shape of the enzyme and is called denaturation.