Digestive enzyme

Encyclopedia : D : DI : DIG : Digestive enzyme

Digestive enzymes are enzymes in the alimentary tract with a purpose of breaking down components of food so that they can be taken up by the organism. The main sites of action are the oral cavity, the stomach, the duodenum and the jejunum. They are secreted by different glands: the salivary glands, the glands in the stomach, the pancreas, and the glands in the small intestines.

Contents

1 Oral cavity
2 Esophagus
3 Stomach
4 Small intestine

4.1 Pancreatic enzymes
4.2 Proper small intestine enzymes

Oral cavity

In the oral cavity, salivary glands secrete pytalin. It is a type of α-amylase, which digests starch into small segments of multiple sugars and into individual soluble sugars. Secreted by small and large salivary glands.

Salivary glands also secrete lysozyme, which kills bacteria but is not classified as a digestive enzyme.

Esophagus

There are no digestive enzymes secreted in the esophagus.

Stomach

The enzymes that get secreted in the stomach are called gastric enzymes. These are the following:

Pepsin is the main gastric enzyme. As it breaks proteins into smaller peptide fragments, it is a peptidase.
Gelatinase, degrades type I and type V gelatin and type IV and V collagen, which are proteoglycans in meat.
Gastric amylase degrades starch, but is of minor significance.
Gastric lipase is a tributyrase by its biochemical activity, as it acts almost exclusively on tributyrin, a butter fat.

Small intestine

Pancreatic enzymes

The pancreas is the main digestive gland in our body. It secretes the enzymes:

Trypsin, is a peptidase, like pepsin in the stomach.
Chymotrypsin, also a peptidase
Carboxypolypeptidase, splits peptide fragments into individual amino acids. It is a protease.
Several elastases that degrade the protein elastin and some other proteins.
Several nucleases that degrade nucleic acids.
Pancreatic amylase that, besides starch and glycogen, degrades also most other hydrocarbons, but not cellulose. Disaccharides and trisaccharides form.

Proper small intestine enzymes

Several peptidases.

Four types of enzymes degrade disaccharides into monosaccharides:

Sucrase, which breaks down sucrose into glucose and fructose.
Maltase, which breaks down maltose into glucose.
Isomaltase, which breaks down maltose and isomaltose.
Lactase, which breaks down lactose into glucose and galactose.
Intestinal lipase, which breaks down fatty acids.

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