What is Pepsin

A digestive protease

Pepsin is a digestive protease secreted by gastric principal cells in the stomach.It works by breaking down the proteins in food into small peptide fragments.The main cells secrete pepsinogen, which is stimulated by gastric acid or pepsin to form pepsin, which is not directly produced by cells.

Concept:

Determination of pepsin can be used to identify neurological hypoacidemia.When it is too little or lacking, the former pepsin content is sometimes normal,while the latter lacks hydrochloric acid and pepsin at the same time.It is generally believed that gastric hypoacidemia is caused by severe organic changes in the gastric mucosa,especially for pernicious anemia, anacidemia, and no pepsin secretion. In chronic gastritis, chronic gastric dilatation, and chronic duodenitis, the secretion of pepsin often decreases. Generally, diseases with high gastric acid-base secretion, such as pepsin, will increase the activity of pepsin.In 1836,Theodor Schwann (Theodor Schwann) discovered an enzyme that can participate in digestion during his research on the digestion process, and named it pepsin.Pepsin was also the first enzyme obtained from animals.The only proteolytic enzyme in the stomach.Its optimum pH value is 1.5-2.0.The main site of pepsin action is the peptide bond formed by the amino group of aromatic amino acid or acidic amino acid.This enzyme is synthesized by the principal cells of the gastric gland and secreted in the form of zymogen granules.After being activated by hydrochloric acid in gastric juice,it has the ability to digest protein.Medicinal pepsin, which can be extracted from the stomach of pigs, cattle, and sheep, is used for indigestion. 

Introduce:

Pepsinogen is secreted by the principal cells of the gastric fundus.Under the condition of pH 1.5-5.0, it is activated into pepsin, decomposes protein into peptides,and partially decomposes into amino acids such as tyrosine and phenylalanine.The determination of gastric juice pepsin can be used to distinguish neurogenic hypoacidemia from gastric hypoacidemia.When there is hypochlorhydria or lack of gastric acid, sometimes the former has normal pepsin content, while the latter lacks hydrochloric acid and pepsin at the same time.It is generally believed that gastric hypoacidemia is caused by serious organic changes in the gastric mucosa, especially pernicious anemia, anacidemia, and absence of pepsin secretion are important diagnostic criteria.In chronic gastritis, chronic gastric dilatation, and chronic duodenitis, the secretion of pepsin often decreases.Generally, diseases with high gastric acid-base secretion, such as duodenal ulcer, increase the activity of pepsin.In 1836, Theodor Schwann (Theodor Schwann) discovered a substance that could participate in digestion while studying the digestion process, and named it pepsin.Pepsin was also the first enzyme obtained from animals.The only proteolytic enzyme in the stomach.Its optimum pH value is between 1 and 2.The main site of pepsin action is the peptide bond formed by the amino group of aromatic amino acid or acidic amino acid.This enzyme is synthesized by the principal cells of the gastric gland and secreted in the form of zymogen granules.After being activated by hydrochloric acid in gastric juice, it has the ability to digest protein.Medicinal pepsin, which can be extracted from pig stomach, is used for indigestion.This medicine is contraindicated in peptic ulcers.Properties this product is white or light yellow powder; no musty smell; hygroscopicity; the aqueous solution is acidic.Identification Take the aqueous solution of this product, add tannic acid, gallic acid or most heavy metal salt solutions, that is, precipitation occurs.Inspection of weight loss on drying Take this product and dry it at 100°C for 4 hours, and the weight loss should not exceed 5.0% (Appendix Ⅷ L).Potency determination Preparation of reference solution Accurately weigh an appropriate amount of tyrosine, dry at 105°C to constant weight, add hydrochloric acid solution [take 65ml of 1mol/L hydrochloric acid solution, add water to make up to 1000ml] to make a solution containing 0.5mg.1ml.

Basic Features:

When pepsin cleaves proteins or polypeptides, it has certain amino acid sequence specificity.For example, it tends to cleave peptide bonds with aromatic amino acids (such as phenylalanine, tryptophan, and tyrosine) or leucine at the amino or carboxyl terminus; when the first amino acid is a basic amino acid (such as lysine acid, arginine, histidine) or when the amino terminus of the peptide bond is arginine, the peptide bond cannot be effectively broken.This cleavage specificity is even more pronounced at pH 1.3: only amino-terminal peptide bonds to phenylalanine or leucine tend to be cleaved.Refers to a digestive enzyme with a molecular weight of 35,000 secreted by the principal cells of the gastric glands.The enzyme is secreted by inactive pepsinogen (Pepsinogen) and activated into pepsin under the action of hydrochloric acid.It can decompose the peptide bonds formed by amino acids such as phenylalanine or tyrosine in proteins, and the products are peptone and a small amount of polypeptides and amino acids.The optimal pH value of the enzyme is around 2.Pepsin has high activity in acidic environment, and its optimum pH value is about 3. In solutions with neutral or alkaline pH, pepsin melts and becomes inactive.Pepsin inhibits the activity of pepsin.