Pepsin (Pepsinum) is an enzyme in the gastric juice. The molecular weight is 35,000. The pepsin molecule consists of 340 amino acid residues. Pepsin hydrolyzes proteins to peptides . The optimal action at a pH of about 2.0. The precursor of pepsin, pepsinogen, produced by the cells of the gastric mucosa, is converted into pepsin in the presence of hydrochloric acid contained in gastric juice. Pepsin - a drug (Pepsinum siccum) - is obtained by extraction from the mucous membrane of the stomachs of pigs, sheep and calves. Apply with hypo-and anacid gastritis, dyspepsia. Pepsin is prescribed orally at a dose of 0.2–0.5 g per reception, 2–3 times a day before meals or with meals as a powder or in a 1–3% solution of diluted hydrochloric acid. Form release: powder.
See also Gastric juice, Enzymes .
In the fundus glands of the stomach, 1 g of pepsinogen is formed daily, which in the cavity of the stomach is activated by the action of hydrochloric acid, turning into pepsin. The molecular weight of pepsinogen is 42,000, pepsin is 35,000. The optimum pH for pepsin is 1.5-2. Most of the enzyme enters the stomach and plays an active role there in the digestive process, but a certain amount of pepsinogen passes into the bloodstream and is excreted by the kidneys.Go
Pepsin breaks down almost all proteins, with the exception of some protamines. Synthetic peptides are also hydrolyzed if there are L-amino acids on both sides of the broken bond. The rest of the specificity in relation to amino acids is negligible, although there is a preference for aromatic amino acids.
Pepsin is an enzyme in gastric juice. Belongs to the group of proteinases (see Protease); obtained in crystalline form. Mol at. 35,000, isoelectric point approx. pH = 1. In addition to pepsin, in the gastric juice (see) there are several related proteolytic enzymes (for example, gastriksin).
The most pure preparations of pepsin are obtained by chromatography on columns with diethylaminoethyl cellulose. The pepsin molecule is a single polypeptide chain of about 340 amino acid residues. Dephosphorylation of pepsin does not destroy its enzymatic activity. Pepsin is most stable at pH = 5-5.5, self-digestion occurs in a more acidic environment. Pepsin hydrolyzes proteins to peptides; Amino acids are also found among the products of hydrolysis. Peptide bonds formed by various amino acid residues undergo hydrolysis. Pepsin is able to catalyze the transpeptidation reaction (transfer of amino acid residues from one peptide to another). The optimum action of pepsin is about pH = 2; at pH = 5, pepsin causes frosting of milk, at pH above 6 it is quickly inactivated.
The inactive precursor of pepsin, a pepsinogen produced by the mucosal cells of the fundus portion of the stomach, is converted to pepsin in the presence of hydrochloric acid contained in the gastric juice. The activation process proceeds autocatalytically with maximum speed at pH = 2. Several peptides are cleaved from the N-terminal part of the pepsinogen molecule with a common mol. at. OK. 8000. A pepsin inhibitor is isolated - a peptide with a mol. at. OK. 3000, which is formed from pepsinogen when it is converted to pepsin. During activation, an intermediate compound of pepsin forms with a polypeptide inhibitor, which easily dissociates at low pH values, and the inhibitor is digested with pepsin. At pH> 5, the dissociation is insignificant and inhibition of pepsin occurs almost in stoichiometric ratios.
Pepsin (drug). Pepsin (Pepsinum siccum) is obtained by extraction from the mucous membranes of the stomachs of pigs, sheep or calves. Applied as a means of replacement therapy in acute and chronic diseases of the digestive tract, accompanied by depletion of gastric juice with endogenous pepsin. For therapeutic use, pepsin is diluted to the official standard (1: 100) with milk sugar. Assign inside adults for 0.2-0.5 g per reception 2-3 times a day before meals or during meals as a powder or 1-3% solution of diluted hydrochloric acid; children - from 0.05 to 0.5 g in a 0.5-1% solution of diluted hydrochloric acid. Form release: powder.