List of Digestive Enzymes

Have you ever thought how food gets digested inside our body after we consume? The internal structure of our body is extremely potent in carrying out numerous functions, amongst which digestion is the most vital of all the processes taking place.

Our body's metabolism is controlled by a group of digestive enzymes, which are secreted by various organs of the digestive system. These enzymes aid in proper digestion of food. Enzymatic digestion begins in the mouth and extends to the intestine, where it gets converted to simpler particles and are then excreted by our body. These digestive enzymes act as catalysts for breakdown of carbohydrates, fats, and proteins.

The Source of Digestive Enzymes

Digestive enzymes help to breakdown polymeric macromolecules into small building blocks, which are required by our body to maintain a healthy life. These enzymes are also present in the saliva, where they assist the first step of digestion. The enzymes are classified on the nature of substrates they work. Digestive enzymes are broadly classified into four groups. They are:

• Proteolytic Enzyme: split proteins to amino acids
• Lipolytic Enzyme: split fats to fatty acids and glycerol
• Amylolytic Enzyme: split carbohydrate and starch to simple sugars
• Nucleolytic Enzyme: split nucleic acids to nucleotides

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 list 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 list 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

Pancreas
Pancreas is the storehouse of digestive enzymes and it is the main digestive gland of our body. The digestive enzymes of the pancreas breakdown carbohydrates and starch molecules to simple sugars. They also secrete a group of enzymes which help in degradation of nucleic acids. It functions both as an endocrine and exocrine gland. The digestive enzymes secreted by pancreas are listed in the table.

Enzymes	Function
Pancreatic lipase	Degrades triglycerides into fatty acids and glycerol
Phospholipase	Hydrolyzes phospholipids into fatty acids and lipophilic substances
Trypsin	Converts proteins to basic amino acids
Steapsin	Breakdown of triglycerides to glycerol and fatty acids
Chymotrypsin	Converts proteins to aromatic amino acids
Carboxypeptidase	Degradation of proteins to amino acids
Pancreatic amylase	Degradation of carbohydrates to simple sugars
Elastases	Degrade the protein elastin
Nucleases	Conversion of nucleic acids to nucleotides and nucleosides

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	Stimulates digestion of proteins and fats
Secretin	Controls secretion of duodenum and osmoregulation
Sucrase	Converts sucrose to disaccharides and monosaccharides
Maltase	Converts maltose to glucose
Lactase	Converts lactose to glucose and galactose
Isomaltase	Converts maltose to isomaltose

After knowing the types of digestive enzymes and their respective functions, I hope you understand how intricately the human digestive system works. The final product of digestion i.e. feces is then transported to the large intestine from where it is expelled.