Two specific roles that enzymes play in cells include being used as ion pumps during active transport, such as the ATPases, and being utilized as receptors for signal transduction, such as kinases and phosphatases. Generally, enzymes function as organic catalysts that speed up biochemical reactions.
The survival of living organisms depends on the various biochemical reactions taking place inside the body. For these reactions to occur, a necessary amount of energy, called the activation energy, is required. Enzymes are protein complexes that reduce the activation energies of different reactions. Without enzymatic activity, reactions are approximately 10 billion times slower compared to those reactions involving the use of enzymes. The catalytic power of high-speed enzymes is said to be up to 500,000 molecules per second.
Enzymes are characterized by a three-dimensional shape that contains an active site where catalysis occurs. A substance called a substrate, specifically binds to a particular enzyme to form a product. Enzymes are not chemically altered nor consumed during the reaction. This important attribute allows enzymes to be utilized repeatedly.
Enzymes serve a variety of biological purposes and industrial applications. Aside from being used as transduction agents and ion pumps, other biological functions of enzymes include cell regulation, formation of metabolic pathways, contraction of muscles and breakdown of complex molecules into simpler substances. Enzymes are also important components in different industries, such as the food, brewing, bio-fuel, rubber and paper industries.