Enzymes

Latest Edit: Hector 2014-02-19 (EDT)

An enzyme is a type of highly specialized protein that acts as a catalyst for a specific chemical reaction in the body.

Enzymes have the ability to induce chemical changes in other substances by rapidly and efficiently speeding up the reaction without being altered themselves in the process.

Function of Enzymes

Enzymes have often been called the “sparks of life” as they play a key role in nearly all of the biochemical activities that occur in the body. Without the catalytic action of enzymes most of the reactions in the body would occur far too slowly for life to be sustained.

Each enzyme has a specialized function that no other enzyme is able to carry out. The chemical shape of each enzyme is specific so that they can only initiate a reaction in a certain substance, called a substrate, or group of closely related substances and not in any others. Each enzyme is named according to the substrate on which it acts and there are numerous enzymes in the body as a result. The naming of enzymes in most cases reveals their function; ‘-ase’ is added to the name either of the substrate on which they act (e.g. peptidasas hydrolase, for enzymes causing hydrolysis). For example sucrase is the enzyme specific to breaking down sucrose.

Many enzymes require added support in the form of a non-protein cofactor in order to perform their specific function. These can take the form of a loosely associated organic compound (e.g. a vitamin; coenzyme) or a tightly bound metal ion (e.g., iron, zinc) or an organic (often metal-containing) group. For example, vitamin C functions as the coenzyme to the enzyme proline hydroxylase which is necessary for collagen synthesis. ,

All enzymes are dependent on the correct environmental conditions in order to function effectively. These factors differ depending on the site at which a particular enzyme acts. Extremes in pH or temperature irreversibly cease enzyme activity, as do some substances that bind to the active sites of particular enzymes. (e.g. cyanide blocks the essential enzyme in mitochondria and causes fatal respiratory failure)

Following are some of the core functions of enzymes in the body: , ,

• Digestive enzymes break down food particles for energy in the body
• Uricolytic enzymes catalyze the conversion of uric acid into urea
• Respiratory enzymes assist in the elimination of carbon dioxide from the lungs
• Utilization of nutrients ingested by the body to construct new muscle tissue, bone, glandular tissue, skin and nerve cells
• Stimulation of the oxidation of glucose which in turn generates energy for the cells in the body
• Protection of blood from toxic waste materials by converting these substances to forms that can be eliminated by the body
• Generation of movement: myosin hydrolyzes ATP to generate muscle contraction
• Provision of assistance to the kidneys, lungs, skin and colon in eliminating toxins and waste
• Concentration of iron in the blood
• Coagulation of blood in order to stop bleeding

Classification of Enzymes

Enzymes can be classified into two groups: Digestive and Metabolic

Digestive Enzymes: are secreted along the gastrointestinal tract and work to break down food so nutrients can be absorbed into the bloodstream.

There are three main categories of digestive enzymes

• Protease: found in stomach, pancreatic and intestinal juices. Break down a long protein into smaller chains called peptides
• Amylase: found in saliva, pancreatic and intestinal juices. Catabolize carbohydrates (starch chains) into smaller sugar molecules. Maltase, lactase, and sucrase then finish breaking the simple sugars down into individual glucose molecules.
• Lipase: found in the stomach and pancreatic juices and aid in the digestion of fat.

Metabolic Enzymes: govern the activities of all of the body’s cells, tissues and organs and catalyze the numerous chemical reactions within the cells of the body (e.g. energy production). These enzymes do specific tasks in the body and therefore each body tissue has its own specific set.

The two most important metabolic enzymes are:

• Superoxide dismutase is an antioxidant which protects the cells by attacking superoxide, a common free radical
• Catalase breaks down the metabolic waste product, hydrogen peroxide and then liberates oxygen so it can be used within the body

Enzyme Dysfunction and Disease

The activity of enzymes is strictly controlled in the body and any sort of malfunction or mutation of a single crucial enzyme can lead to a genetic disease. An example of this is phenylketonuria in which there is a mutation of a single amino acid in the enzyme phenylalanine hydroxylase, which catalyzes the first step in the degradation of phenylalanine. This mutation results in the build-up of phenylalanine and related products which can lead to mental retardation if the disease is untreated.

Enzyme dysfunction is most often experienced in the digestive system as it secretes a wide array of enzymes that work to break down food into its constituent nutrients. These digested nutrients then pass from the intestine to the bloodstream. The pancreas and small intestine produce the majority of the digestive enzymes, and deficiencies in the production, release or function of these enzymes can lead to a variety issues and symptoms in the body.

Following are the most common symptoms of digestive enzyme deficiencies:

• Abdominal gas, distention and flatulence: This symptom is often seen in people with lactase deficiencies. If this enzyme is not present or insufficient, lactose does not get adequately broken down and builds up in the intestine. Bacteria will then break down the undigested lactose which leads to production of hydrogen, carbon dioxide and methane in the colon. The excess gas often causes a rumbling noise and sensation ( borborygmi) as it moves through the intestine.

• Diarrhea: is a common symptom caused by digestive enzyme deficiencies. Normally, the majority of water in the intestine is reabsorbed, leaving a semi-solid stool. With digestive enzyme deficiencies however, undigested food causes increased stool water content, resulting in diarrhea. Conditions associated with digestive enzyme deficiencies and diarrhea include: carbohydrate enzyme deficiencies, acute and chronic pancreatitis, cystic fibrosis, pancreatic tumors.

• Unintentional Weight Loss: Individuals with digestive enzyme deficiencies are not able to break down one or more types of food components into an absorbable form. Consequently, the undigested food provides no nutrient or caloric value to the individual, and unintentional weight loss results. The diarrhea that commonly accompanies digestive enzyme deficiencies further contributes to weight loss.

• Steatorrhea (fatty stool): This symptom typically occurs in individuals with a pancreatic digestive enzyme deficiency. The pancreas secretes lipase, an enzyme that breaks down dietary fats, and if absent most of the fat ingested in the diet will pass directly through the intestine into the stool. Individuals with steatorrhea typically notice their stool has an oily appearance, floats in the toilet bowl and has a distinctive, foul odour. Pancreatic disorders associated with steatorrhea include: acute and chronic pancreatitis, cystic fibrosis and pancreatic cancer.

Specific Consideration

• All enzymes and most vitamins are extremely sensitive to heat and are often destroyed during the pasteurization and cooking process. Where possible fruits and vegetables should be eaten raw or lightly steamed.

• Oral administration of enzymes can sometimes be effective in the treatment of diseases such as pancreatic insufficiency and lactose intolerance.