Enzymes act as biological catalysts, allowing all the chemical reactions of metabolism to take place, regulating the speed at which they progress, and providing a means of controlling individual biochemical pathways.
Enzymes owe their activity to the precise three-dimensional shape of their molecules.
A chemical reaction takes place at this site and the products are released, leaving the enzyme unchanged and ready for re-use. This cycle can be repeated as often as 100,000 times per second. Enzymes are very specific in relation to the substrates with which they work, and are normally only effective for one reaction or a group of closely related reactions. Many enzymes need a coenzyme in order to function. The human body contains at least 1,000 different enzymes.