Enzymes are proteins that are catalysts of chemical reactions. From Chemistry, it is called that catalysts are non-consumable substances that decrease the activation energy essential for a chemical reaction to occur.

Enzymes are highly particular to the reactions they catalyze. They are of essential importance for life because most part of chemical reaction of the cells and tissues are catalyzed by enzymes. Without enzymatic action, those reactions would not happen or would not happen in the needed speed for the biological processes in which they participate.