Enzymes are proteins that catalyze biochemical reaction with high specificity, converting substrates into products with increased reaction rate. Enzyme catalysis is involved in almost all metabolic processes in the cell, where the reaction rate must be fast enough to sustain life.

As a type of catalyst, enzymes are not consumed in biochemical reactions, nor do they alter the equilibrium of a reaction. They increase the reaction rate by lowering the activation energy, making the conversion of substrate to product occur much faster. The enzyme activity can be affected by various factors, for example, temperature, pH as well as other molecules such as inhibitors and activators.