Engaging Enzymes
An '''enzyme''' is a protein that catalyzes, or speeds up, a chemical reaction. An enzyme interacts with a substrate
(molecule) to lower the energy needed for it to react. This results in a new product and the enzyme, unchanged.
Enzymes are essential to sustain life because most chemical reactions in living cells would occur too slowly, or would lead
to different products, without enzymes. A malfunction (mutation, overproduction, underproduction or deletion) of a single
critical enzyme can lead to a severe disease. For example, phenylketonuria is caused by a malfunction in the enzyme
phenylalanine hydroxylase, which catalyses the first step in the degradation (breakdown) of phenylalanine, an amino acid.
If this enzyme does not function, the resulting build-up of phenylalanine leads to mental retardation.
Like all catalysts, enzymes work by lowering the activation energy of a reaction, thus allowing the reaction to proceed
much faster. Enzymes may speed up reactions by a factor of many thousands. An enzyme, like any catalyst, remains
unchanged by the reaction and can therefore continue to function.
Several factors affect the rate at which enzymatic reactions proceed - temperature, pH, enzyme
concentration, substrate concentration, and the presence of any inhibitors or activators.
Enzyme activity can also be affected by other molecules. Inhibitors are molecules that decrease or stop enzyme activity;
activators are molecules that increase the activity. Inhibitors can be either natural or man-made. Many drugs are enzyme
inhibitors. Aspirin, for example, inhibits an enzyme that produces the inflammation messenger prostaglandin, thus
suppressing pain and inflammation.
Enzymes are also used in everyday products such as washing detergents, where they speed up chemical reactions
involved in cleaning the clothes (for example, breaking down starch stains).
More than 5,000 enzymes are known. To name different enzymes, scientists typically uses the ending ''-ase'' with the