Uses of Digestive Enzyme

Digestion breaks the food we eat down into a form that can be absorbed and used by the body. This process begins in the mouth, continues in the stomach and ends in the small intestine. While the large intestine is part of the digestive system, it does not break down food; it absorbs water and vitamins produced by bacterial action and excretes waste. Every step of the way, digestion in the mouth, stomach and small intestine is facilitated by enzymes that chemically break apart carbohydrates, proteins, and lipids.

Definition

• Enzymes are proteins that are capable of causing chemical changes in other substances without being changed themselves. They help to build compounds as well as break them down, and speed-up chemical reactions in the body. Enzymes are very specific---they act only upon a certain substance. Because of this specificity, they are often named after the substance they affect or the type of reaction they facilitate; an "ase" is added to name the enzyme. For example, a lipase is an enzyme that breaks down lipids. High or low temperatures, heavy metals, and dehydration can all slow down or stop enzymatic activity.

Digestive Enzymes in the Mouth

• As food is physically broken into small pieces by chewing, the salivary glands release an enzyme called "salivary amylase." It begins the breakdown of carbohydrates. The carbohydrates we eat are polysaccharides, meaning they are long chains of monosaccharides. The only form that can be absorbed into the blood stream and used for energy is the monosaccharide, so amylase in the mouth starts to break the long chains into smaller pieces.

Digestive Enzymes in the Stomach

• The digestion of proteins in the stomach starts with gentle muscular contractions that mix food with secretions released from glands in the stomach. The result is a thin liquid called "chyme." Then, hydrochloric acid and pepsinogen are secreted into the stomach where they combine to create pepsin. Pepsin is the digestive enzyme in the stomach that breaks the bonds between the amino acids that form proteins. Gastric lipase is another enzyme found in the stomach. Its purpose is to split the fat molecules in milk, but since it doesn't function well in such an acidic environment, it has a minimal role. Infants have a stomach enzyme that is absent in adults called "rennin." It causes milk in the stomach to thicken and curdle, thus slowing it down and helping the digestive process.

Digestive Enzymes in the Small Intestine

• As chyme leaves the stomach and enters the small intestine, carbohydrates and proteins are only partially broken down. Digestion of lipid (fats) only occurs in the small intestine. Many enzymes that originate in both the pancreas and the small intestine continue the process of digesting carbohydrates and proteins. Pancreatic amylase, maltase, sucrase and lactase ensure all carbohydrates are reduced to monosaccharides of glucose and fructose. The digestion of protein continues with trypsin, chymotrypsin, carboxypeptidase and erepsin, all of which work together to reduce proteins into single amino acids that can be absorbed. Lipid digestion begins with bile from the liver that breaks large pieces of fats into smaller droplets. Then, an enzyme called "pancreatic lipase" breaks each fat molecule down into its component parts. All of the nutrients from carbohydrates, proteins, and lipids are digested and absorbed into the blood stream in the small intestine.

Sources of Digestive Enzymes

• Just like any other protein, enzymes are built in the body from the essential amino acids provided in foods we eat. Fruits and vegetables contain enzymes but since heat harms enzymes, they must be eaten raw. Factors such as disease, aging, and alcohol abuse can interfere with the natural production of enzymes, in which case enzyme supplements may be necessary to help the digestive process. The key to remember is that no matter how diligently we work to eat a balanced diet, our bodies can only benefit from the food we eat if it has an adequate supply of the digestive enzymes needed to break that food down into usable units.