Pepsinogen

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Pepsinogen, synthesized by the main cells of the oxyntic glands, in the gastric cavity through the action of hydrochloric acid (HCL) or active pepsin (pepsin) into pepsin, decomposing protein into fat, peptone and a small amount of peptides. The optimal pH of the enzyme action is 2, after entering the small intestine, the enzyme activity is lost.

Introductions

Pepsin assay can be used to identify neuropathic hypoacidity. When it is too low or lacking, the content of pepsin in the former is sometimes normal while the content of hydrochloric acid and pepsin in the latter is deficient at the same time. It is generally believed that gastric hypoacidity is caused by severe organic changes in the gastric mucosa, especially for pernicious anemia, anaemia, and lack of pepsin secretion, which are important diagnostic findings. The secretion of pepsin in chronic gastritis, chronic gastric dilatation, and chronic duocholitis often decreases. Generally, diseases with high basal secretion of gastric acid, such as, etc., have increased pepsin activity. In 1836, (Theodor Schwann) in the study of the digestive process, discovered a kind of ability to participate in digestion, and named it pepsin. Pepsin was also the first enzyme obtained from animals. The only proteolytic enzyme in the stomach. The optimal pH is 1.5 to 2.0. The main part of the action of pepsin is the peptide bond composed of the amino group of aromatic amino acid or acidic amino acid. This enzyme is synthesized by the main cells of the gastric glands and secreted in the form of zymogen particles. After being activated by hydrochloric acid in the gastric juice, it has the ability to digest proteins. Medicinal pepsin can be extracted from the stomachs of pigs, cattle and sheep for indigestion.

Figure 1. Protein structure of pepsin.

Composition

Pepsinogen is the precursor of pepsin. According to its biochemical properties and immunogenicity, it can be divided into two subgroups. The immunogenicity of 1-5 components is the same, called pepsinogen I, which is mainly composed of gastric fundic glands. Secreted by principal cells and mucous neck cells; components 6 and 7 are called pepsinogen II. Except for secreted by principal cells and mucous neck cells of fundus glands, mucous neck cells of cardia and pyloric glands of gastric antrum and ten Pepsinogen II can also be produced in the upper diodenum.

Metabolism

Under normal circumstances, about 1% of PG enters the blood circulation through the capillaries of the gastric mucosa, and the PG entering the blood circulation is very stable in the blood. Serum PG I and PG II reflect the number of gastric mucosa glands and cells, and indirectly reflect the secretory function of different parts of the gastric mucosa. When the gastric mucosa undergoes pathological changes, the serum PG content also changes. Therefore, monitoring the concentration of PG in serum can be used as a means to monitor the state of the gastric mucosa. Pepsinogen is synthesized by the host cell and stored in the cell in the form of inactive zymogen particles. When the cell is full of zymogen particles, it has a negative feedback effect on the production of new zymogen. The pepsinogen secreted into the stomach cavity is under the action of gastric acid to separate a small molecule of polypeptide from the molecule and convert it into active pepsin. The activated pepsin also activates pepsinogen. Pepsin can hydrolyze protein in food. It mainly acts on peptide bonds containing phenylalanine or tyrosine in protein and polypeptide molecules. The main decomposition product is peptone, which produces less polypeptides or amino acids. Pepsin only works in a more acidic environment, and its optimal pH is 2. As the pH increases, the activity of pepsin decreases, and when the pH rises above 6, the enzyme undergoes irreversible denaturation.