Protein Gastric juice

A biochemical catalyst is called an enzyme. Enzymes are specialized proteins that catalyze specific biochemical reactions. Some enzymes are found in extracellular fluids such as saliva and gastric juices, but most are found inside cells. Each type of cell has a different array of enzymes that act together to determine what role the cell plays in the overall biochemistry of the organism. Enzymes are complicated molecules. Biochemists have determined the molecular structures of some enzymes, but the structures of many enzymes are not yet known. 

The hydrochloric acid in gastric juice is important for digestion. It activates pepsinogen to form pepsin (see below) and creates an optimal pH level for it to take effect. It also denatures food proteins so that they are more easily attacked by proteinases, and it kills micro-organisms. 

Retief, F. P., Gottlieb, C. W., Kochwa, S., Pratt, P. W., and Herbert, V., Separation of vitamin Birbinding proteins of serum, gastric juice and saliva by rapid DEAE cellulose chromatography. Blood 29, 501-516 (1967). 

Pepsin. A general name for several names of the gastric juice that catalyze the hydrolysis of the protein to form polypeptides. 

Guerin, D., Vuillemard, J.C., Subirade, M. (2003). Protection of bifidobacteria encapsulated in polysaccharide-protein gel beads against gastric juice and bile. Journal of Food Protection, 66, 2076-2084. 

The digestion of proteins begins in the stomach, which secretes gastric juice—a unique solution containing hydrochloric acid and the proenzyme, pepsinogen ... 

A clinical sample (whole blood, serum, plasma, urine, gastric juice, bile fluid, sweat, etc.) differs from any other analytical sample because of the presence of heterogeneous organic (e.g., proteins) and organic or inorganic components (e.g., urea or sodium ion), sample changes in time (owing to, e.g., denaturation of proteins, escape of C02) and small sample size (even a few tens of microliters). 

Protein digestion starts in the mouth and continues in your stomach and small intestines. This is due to pepsin, which is secreted in the saliva and obviously the gastric juice, followed by pancreatic enzymes, then absorbed by the mucosal cells in the small intestines. In short, the digestive system breaks down protein into its peptide amino acid structures so they can be absorbed in the small intestine via the... 

A major aim of enteric coating is protection of drugs that are sensitive or unstable at acidic pH. This is particularly important for drugs such as enzymes and proteins, because these macromolecules are rapidly hydrolyzed and inactivated in acidic medium. Antibiotics, especially macrolide antibiotics like erythromycin, are also rapidly degraded by gastric juices. Others, such as acidic drugs like NSAID s (e.g., diclofenac, valproic acid, or acetylsalicylic acid) need to be enteric coated to prevent local irritation of the stomach mucosa. 

In clinical work many biological fluids have been submitted to paper electrophoretic separation. Serum and urine have been studied extensively and the results were reviewed in Volume I of this series (p. 238). Other fluids include cerebrospinal fluid (B12, B14, E6, K18), pleura] fluid (D4), gastric juice (H6), ascitic fluid (H9), synovial fluid (W3), proteins of the lens (F4, W9, W10), aqueous humor of the eye (W12, W24), edema liquid (W23), and pericardiac effusion (G2). Apart from the general separation of plasma proteins, work has been done on special protein groups, such as lipo- and glycoproteins, muco-proteins, hemoglobins (H19), coagulation factors (05), and on other components, such as amino acids. 

These have been found in saliva, amniotic fluid, plasma, granulocytes, platelets, milk, and gastric juice, and it was suggested by Stenman (S8) that the R-protein in these different cells and fluids is a single microhetero-... 

Answer Pepsin proteins have a relatively low pi (near the pH of gastric juice) in order to remain soluble and thus functional in the stomach. (Pepsin—the mixture of enzymes—has a pi of 1.) As pH increases, pepsins acquire a net charge and undergo ionic interactions with oppositely charged molecules (such as dissolved salts), causing the pepsin proteins to precipitate. Pepsin is active only in the stomach. In the relatively high pH of the intestine, pepsin proteins precipitate and become inactive. 

Crews et al. [81] studied cooked cod by means of a two-step in vitro gastrointestinal enzymolysis. For the first step of sample preparation they employed gastric juice (1 percent m/v pepsin, pH = 2.0, in 0.15 mol l-1 NaCl) at 37°C for 4 h. Afterwards a pancreatin-based mixture was added to the sample solution containing 1.5 percent m/v pancreatin, 0.5 percent m/v amylase, and 0.15 percent m/v bile salts in 0.15 mol l-1 NaCl at pH = 6.9 for a further 4 h at 37°C. The relatively short (8 h) enzymatic activity and the lack of enzymes capable of hydrolyzing proteins directly into amino acids resulted in the identification of inorganic Se (IV) only, as no selenoamino acids could be detected. 

The entry of protein into the stomach stimulates the release of a hormone, gastrin, which then causes the release of hydrochloric acid from the parietal cells, and pepsinogen from the chief cells (Fig. 15-5). Pepsinogen is another zymogen (they all start with pro- or end in -ogen) that is converted in the gastric juice to the active enzyme pepsin. 

Accumulation of osmotically-active chloride (which is required to maintain electroneutrahty with hydrogen ions) in the canaliculi generates an osmotic gradient that results in outward diffusion of water the resulting gastric juice is about 155 mM HCl and 15 mM KCl, with a small amount of NaCl. The highly acidic enviromnent causes denaturation of proteins, making them susceptible to proteolysis by pepsin (which is itself acid-stable). 

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