Mouth
-the oral cavity or the mouth contains salivary glands that secrete a wide range of enzymes to aid the first step of metabolism of food. The salivary gland secretes the enzyme lysozyme which has an antibacterial action. The enzymes secreted by the mouth mainly provide protection against bacteria. Betaine helps to maintain a fluid balance inside the mouth. The lists of digestive enzymes secreted by the oral cavity are mentioned in the table. Enzymes | Function | Ptyalin | Converts starch to simple soluble sugars | Amylase | Converts starch to soluble sugars | Betaine | Maintains cell fluid balance as osmolytes | Bromelain | Anti-inflammatory agent, tenderizes meat |
Stomach -the enzymes released by the stomach are known as gastric enzymes. They are responsible for breaking down complex macromolecules like proteins and fats into simpler compounds. Pepsinogen is the main enzyme of the stomach and its active form is pepsin. Stomach secretes hydrochloric acid which kills bacteria and germs and provides an acid environment for proper enzymatic activity of protease enzymes. The lists of digestive enzymes secreted by the stomach are mentioned below. Enzymes | Function | Pepsin | Breaks protein into small peptides | Gastric amylase | Degradation of starch | Gelatinase | Degradation of gelatin and collagen present as proteoglycans in meat | Rennin | Conversion of liquid milk to solid particles | Gastric lipase | Degradation of butter fat |
Small Intestine -the final step of digestion is carried out by the small intestine. It contains a group of enzymes that breakdown the products undigested by the pancreas. This takes place just prior to excretion. The food gets converted to semi-solid form by the activity of the enzymes present in the duodenum, jejunum, and ileum. The enzymes functioning in this part of the digestive system are mentioned below. Enzymes | Function | Cholecystokinin |