Enzymes are proteins produced by all living organisms, and, like all proteins, they consist of amino acids. What makes these proteins different from other proteins is how they behave in the body. By definition, enzymes are catalysts that make many essential biochemical reactions ‘happen’ and are not used up or chemically altered in the process. As a catalyst, they help a chemical reaction take place quickly and efficiently. Some reactions would either happen very slowly or not occur at all without enzymes. So a little bit of enzyme can effect a big change.