Digestive Enzyme: Function & Diseases

Digestive enzymes are enzymes responsible for breaking down food. They process long-chain molecules into short-chain molecules so that they can be utilized by the metabolism. Most digestive enzymes are produced in the pancreas.

What is a digestive enzyme?

Enzymes act as biocatalysts in the human body. This means that they can initiate and accelerate chemical reactions. Digestive tract enzymes are responsible for breaking down food components. Digestive enzymes can be divided into peptidases, glycosidases, lipases and nucleases.

Function, action, and tasks

Peptidases can cleave proteins. The peptidases of the human body are pepsin, trypsin, chymotrypsin B, pancreatic elastase, and erepsin. Except for pepsin, all peptidases are produced by the pancreas. Glycosidases serve to cleave polysaccharides, i.e. carbohydrates. Glycosidases include salivary amylase, pancreatic amylase, sucrase isomaltase and maltase glucoamylase. With the help of salivary amylase (α-amylase), carbohydrate digestion can begin in the mouth. Pancreatic amylase, also an α-amylase, then continues the breakdown in the small intestine. Lipases are digestive enzymes that originate from the pancreas and break down fats in the small intestine. The most important lipases are bile salt-activated lipase and pancreatic lipase. Pancreatic lipase breaks down triglycerides to monoglycerides. Nucleases, on the other hand, are enzymes that cleave nucleic acids. A specific enzyme that breaks down milk sugar (lactose) into galactose and glucose is lactase.

Formation, occurrence, and properties

Most digestive enzymes are formed in the pancreas. More specifically, they are produced in the exocrine part of the pancreas. From there, they enter the small intestine through the small ducts of the pancreas and ultimately through the large pancreatic duct. Salivary amylases are produced by the salivary glands. They enter the oral cavity along with saliva. Pepsin is the only digestive enzyme produced in the stomach. It is formed in the main cells of the gastric fundus. Pepsin shows its highest activity at a low pH. This is guaranteed by the acidic stomach acid.

Diseases and disorders

A deficiency of digestive enzymes usually leads to digestive disorders. Thus, a deficiency of lactase results in lactose intolerance. This is also known as lactose intolerance. As a result of the processing disorder in the small intestine, flatulence, abdominal cramps, nausea, diarrhea and vomiting occur. Nonspecific symptoms such as fatigue, depression, inner restlessness, dizziness, nervousness or sleep disorders can also be signs of lactose intolerance. The more lactose the affected person consumes, the more severe the symptoms become. If lactose intolerance is not treated or milk and dairy products are not avoided, the permanent irritation of the intestinal mucosa can lead to malabsorption. This can result in reduced absorption of vitamins, minerals and trace elements. A disease associated with insufficient production of digestive enzymes is pancreatic insufficiency. In children, the most common cause of pancreatic insufficiency is cystic fibrosis. Adults usually develop pancreatic insufficiency after acute inflammation (pancreatitis). When the pancreas is damaged, it lacks digestive enzymes. This leads to a significant disturbance of digestion (maldigestion). As a result, atrophy of the intestinal villi also occurs. Local inflammations develop and harmful bacteria often settle in the area of the small intestine. All this leads to massive digestive disorders with diarrhea or foul-smelling fatty stools. Those affected lose more and more weight. Even with increased food intake, they are unable to gain weight. If too little vitamin K can be absorbed in the intestine, there may also be an increased tendency to bleed. The secretin-pancreozymin test can be used to directly assess the production of digestive enzymes by the pancreas. For this purpose, a probe is inserted into the duodenum. Over a quarter of an hour, this probe is used to aspirate the secretion of the pancreas and examine it for the content of sodium bicarbonate. The activity of the two enzymes pancreatic amylase and pancreatic lipase are also measured.In the first test stage, the patient is then injected with the hormone secretin. This should actually increase secretion. Subsequently, the level of bicarbonate and the activities of the enzymes are determined again. In the second test phase, pancreocymin is administered. Again, the contents of the pancreatic secretion are then measured. Based on the results, pancreatic insufficiency with a deficiency of digestive enzymes can be diagnosed very accurately. A detailed medical history is the first step when a disease affecting the digestive enzymes is suspected. The physician is interested in whether the stool is greasy and shiny, whether diarrhea occurs, whether inflammations of the pancreas are known, whether fatty foods are tolerated, and also whether medication is taken. The medical history is then usually followed by a physical examination. The physician will carefully palpate the abdomen. In this way, he can feel air accumulations or hardening. The examiner can best detect abdominal sounds with a stethoscope. The doctor also inspects the skin. In diseases of the pancreas, yellowing of the eyes and skin may occur if the liver is involved. However, further examinations are usually possible to clarify the underlying disease. In addition to imaging procedures such as computer tomography (CT) and magnetic resonance imaging (MRI), blood and stool are also examined. If pancreatic insufficiency is suspected, however, the stool examination in particular is of great importance. This is because the activity of the two pancreatic enzymes elastase and chymotrypsin can only be detected in the stool. In pancreatic insufficiency, both digestive enzymes are decreased in the stool. A deficiency of digestive enzymes can also occur in the stomach. Here, pepsin is particularly affected. The enzyme pepsin breaks down protein in the stomach under the influence of hydrochloric acid. Heartburn is caused not only by too much stomach acid, but also by a lack of stomach acid. If there is too little stomach acid, the digestive enzyme pepsin cannot be activated. As a result, proteins in the stomach cannot be prepared for further digestion in the small intestine and fermentation processes occur. Typical symptoms include bloating, upper abdominal flatulence, feelings of weakness, hemorrhoids, acne, iron deficiency, protein and zinc deficiency, fungal infections and chronic gastrointestinal infections.