Enzymes are organic compounds (made up primarily protein) that act as catalysts to speed up chemical reactions. In the digestive system, enzymes constantly perform numerous chemical reactions. Each plays a specific role in certain sections to allow optimal breakdown, transport and absorption of nutrients.
Amylase
Amylase is a starch-digesting enzyme that is produced by salivary glands and the pancreas. It breaks down starch into simpler carbohydrates. When you chew a cracker for a long time, you can taste the gradually increase in sweetness as starch is broken into sweeter sugars. In the small intestines, pancreatic amylase digests sugars into glucose for absorption into the bloodstream.
Lipoprotein Lipase
Lipoprotein lipase is an enzyme that is attached to the outer endothelial cells of the capillaries. It breaks down triglycerides to free fatty acids and glycerol (basic components of fats), allowing transport into the bloodstream.
Pepsin
Pepsin is produced by the stomach to digest protein. It attacks polypeptides (complex protein chains) and breaks them down into shorter amino acid chains. Pepsin's inactive form is pepsinogen that rests in the gastric chief cells of the stomach linings. The chief cells store the pepsinogen. Hydrochloric acid (released from parietal cells in the stomach lining) in the stomach during digestion causes the release of pepsinogen, which becomes the active enzyme pepsin.
Trypsin, Chymotrypsin, Carboxypeptidase
Trypsin, chymotrypsin, carboxypeptidase are three digestive enzymes that are secreted by the pancreas to act in the small intestines. They work together to divide short peptides into amino acids that are absorbed in the small intestines.
Alcohol Dehydrogenase
Alcohol Dehydrogenase (ADH) is an alcohol-metabolizing enzyme that is produced in the liver. According to the National Institute on Alcohol Abuse and Alcoholism, women's blood alcohol concentration (BAC) is higher than men after drinking the same amount of alcohol as men. Also, men metabolize more alcohol (30 percent of ingested alcohol) than women (10 percent) because women produce less ADH than men. Compared to Caucasians, some Asians and many Native Americans make relatively little ADH, rendering them to be less tolerable to alcohol.
Glutathione Peroxidase
Glutathione peroxidase, a selenium-containing enzyme, works with vitamin E to reduce free radicals, which are short-lived, unstable compounds that attack cell membranes by taking an electron from them.
Sugar Enzymes
There are four types of enzymes that breaks down sugar molecules in the small intestines. Sucrase breaks down sucrose into glucose and fructose; maltase breaks down maltose into glucose; isomaltase breaks down maltose and isomaltose.
Lactase in an enzyme that breaks down lactose (milk sugar) into glucose and galactose in the villi of the small intestines. People who lack this enzyme suffer from lactose intolerance, which causes stomach cramps, bloating and flatulence.
All of these enzymes break down sugars through hydrolysis, process where water is split into hydrogen cations (H+) and hydroxide anions (OH-). This process breaks polymer bonds in complex sugars into simple sugars.
References
- "Perspectives in Nutrition": Gordon Wardlaw and Margaret Kessel: 2002
- "Biology, 8th edition": Neil Campbell, Jane B. Reece: 2007
- DUI.com
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