Enzyme

An enzyme is an organic catalyst. A catalyst is something that participates in a chemical reaction, but is unchanged by it. Enzymes make biochemical reactions possible. They are complex proteins that are capable of acting independently. Enzymes also act specifically, that is to say that a given enzyme will only work on a specific substance or group of closely related substances. The best known use of enzymes by the body is for digestion; enzymes break down fats, starches and proteins using a process called hydrolysis. Sometimes enzymes need another substance in order to become active. An example of this is the digestive enzyme pepsin, which requires hydrochloric acid to make it active (inactive pepsinogen becomes active pepsin in the presence of hydrochloric acid). Sometimes enzymes need another substance to become active. Very often a vitamin or mineral plays this role, and they are called cofactors.