Enzymes are biomolecules that catalyze biochemical reactions in which a reactant is converted to a specific product type.
Like all catalysts, enzymes work by lowering the activation energy for a reaction, thus dramatically increasing the rate of the reaction. They are not consumed by the reactions they catalyze. However, enzymes do differ from most other catalysts by being specific for the class of reactant they will recognize. This allows for a very targeted reaction, eliminating any concern over the production of hazardous byproducts or secondary waste.
Enzymes offer substantial advantages over chemical catalysts in traditional industrial environments. They are biodegradable, offer a wide range of novel functionalities, work under mild conditions, and often can provide benign alternatives to existing processes.