Enzymes are defined as proteins that expedite the rate of biochemical reactions. While you eat, you are typically attempting to digest and absorb three main nutrients: carbohydrates, proteins and fats. As such, there are three main digestive enzymes to activate these nutrients for either immediate energy or storing for later use.
Amylases
There are actually two enzymes that work to digest major carbohydrates such as starch. The first enzyme is salivary amylase, which is present in some animals such as humans. This enzyme is released while you chew your food to begin breaking down the carbohydrates. After the mashed food is ingested, the major enzyme, pancreatic amylase, acts in the small intestine to absorb monosaccharides that were broken down from the carbohydrates to produce glucose. Upon absorption, intestinal cells transport the glucose to the liver to enter your bloodstream.
Proteases
A complex system of pancreatic enzymes are released into your body's small intestine to digest the proteins you eat in order to utilize their valuable amino acids. These enzymes are called protease enzymes, and the key proteases are trypsin and chymotrypsin. The digestion of proteins is commenced by pepsin in your stomach. Upon reaching the small intestine, trypsin and chymotrypsin are activated into trypsinogen and chymotrypsinogen, respectively, by the protease enterokinase to begin breaking down the protein into peptides. Then the protease carboxypeptidase and peptidase cells digest the peptides into amino acids. Finally, amino acids are routed to the liver and into your blood.
Lipases
Triacylglycerols, more commonly known as triglycerides, are found in fats and are much more difficult to digest than carbohydrates and protein because they are not as soluble in water. Pancreatic lipase converts triglycerides into 2-monoglyceride and two free fatty acids. Abundant amounts of bile salts in the intestine interact to create micelles out of these molecules. They then form back into triglycerides when the micelles enter intestinal cells. Because they are not very water soluble, but still need to be able to combine with your blood, the triglycerides are confined with proteins, phospholipids, cholesterol and other compounds into lipoprotein complexes called chylomicrons. Chylomicrons then enter the lymph and finally the bloodstream.
Final Destinations
Glucose, amino acids and chylomicrons are each in a carbon skeleton form to enable oxidation for energy. If not oxidized for energy, glucose is then stored as glycogen in your liver and muscles. Glucose may also join in the chylomicron-triglyceride process. If not used for energy in oxidation, amino acids are converted back to proteins in cells or are used to produce nitrogen-containing compounds like neurotransmitters and heme. When they are not oxidized, triglycerides are mainly stored as fatty tissue.
References
- "Marks' Basic Medical Biochemistry: A Clinical Approach"; Michael Lieberman, Ph.D.; Allan D. Marks, M.D.; 2009
- Colorado State University: Exocrine Secretions of the Pancreas
