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Pepsin solubility

Just as individual amino acids have isoelectric points, proteins have an overall p/ because of the acidic or basic amino acids they may contain. The enzyme lysozyme, for instance, has a preponderance of basic amino acids and thus has a high isoelectric point (p/= 11.0). Pepsin, however, has a preponderance of acidic amino acids and a low- isoelectric point pi 1.0). Not surprisingly, the solubilities and properties of proteins with different pi s are strongly affected by the pH of the medium. Solubility- is usually lowest at the isoelectric point, where the protein has no net charge, and is higher both above and below the pi, where the protein is charged. [Pg.1024]

Many extracellular proteins like immunoglobulins, protein hormones, serum albumin, pepsin, trypsin, ribonuclease, and others contain one or more indigenous disulfide bonds. For functional and structural studies of proteins, it is often necessary to cleave these disulfide bridges. Disulfide bonds in proteins are commonly reduced with small, soluble mercaptans, such as DTT, TCEP, 2-mercaptoethanol, thioglycolic acid, cysteine, etc. High concentrations of mercaptans (molar excess of 20- to 1,000-fold) are usually required to drive the reduction to completion. [Pg.97]

Jones, D.I.H. and Hayward, M.V. (1975) The effect of pepsin pre-treatment of herbage on the prediction of dry matter digestibility from solubility in fungal cellulase solutions. Journal of the Science of Food and Agriculture 26, 711-718. [Pg.213]

Magnesium carbonate is most water soluble and reacts with hydrochloric acid at a slow rate. Magnesium hydroxide has low water solubility. It reacts with hydrochloric acid promptly. Magnesium trisilicate has low solubility and has the power to adsorb and inactivate pepsin and to protect the ulcer base. [Pg.261]

Hermansson et al. (36) used pepsin and papain to solubilize rapeseed protein concentrate. Papain had a lower solubilizing effect than did pepsin. However, the fact that pepsin has an optimum pH for activity at about 1.6, far below the pH range of most foods, made it possible to study the effects of controlled hydrolysis. At pH 7.0, all hydrolysates were more soluble than the original rapeseed protein concentrate. [Pg.286]

PROTEASE. A proteolytic enzyme that weakens or breaks the peptide linkages in proteins, They include some of the more widely known enzymes such as pepsin, trypsin, ficin, bromelm, papain, and rennin. Being water soluble they solubilize proteins and are commercially used for meat tendenzers, bread baking, and digestive aids. [Pg.1371]

Hypertensin is soluble in alcohol, glacial acetic acid, phenol, and water, and insoluble in ether (61). Because it is inactivated by tyrosinase it probably contains a catechol or phenol group, and by amine oxidase, an amine group on an a-carbon atom (Figure 2). Hypertensin is inactivated by certain phenolic, catecholic, and amine oxidases, by pepsin, trypsin, chymotrypsin, and carboxypeptidase, and by hypertensinase found in plasma. The nature of hypertensinase is unknown, but it is probably not an oxidative enzyme. Because it is heat-labile, hypertensinase can be removed from blood and renin preparations by heating hypertensin itself is heat-stable. Lack of pure preparations of hypertensin has delayed its further chemical identification. [Pg.9]

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. [Pg.33]

Figure 1. Optimum pH of pepsin partially purified from the stomach lining of arctic cod 30°C ( ) 5°C (A) A 280 = absorbancy of TCA solubles at 280 nm. Pepsin was assayed with acid-denatured hemoglobin (2%) at the indicated temperatures and activity was monitored by measurements of TCA-solu-ble products (53). Figure 1. Optimum pH of pepsin partially purified from the stomach lining of arctic cod 30°C ( ) 5°C (A) A 280 = absorbancy of TCA solubles at 280 nm. Pepsin was assayed with acid-denatured hemoglobin (2%) at the indicated temperatures and activity was monitored by measurements of TCA-solu-ble products (53).
These surface films of proteins are not infrequently formed on solutions in which the proteins are quite soluble, so that it may be argued that the protein has been altered or denatured by its unfoldment in the surface film, in such a way as to render it less soluble or completely insoluble. Whether the unfoldment and spreading of the molecule always results in the loss of solubility is not proven Gorter has been able to remove pepsin from a surface on which it has been spread by means of a fine net pulled up through the surface, and subsequently dissolved the material in water, finding that it retained its normal properties, including proteolytic activity. [Pg.90]

Whether enzymes retain their specific chemical activities when spread as a monolayer is still doubtful. Pepsin, spread on water and then deposited on a metal plate, clots milk vigorously when the plate is dipped in the milk the clotting occurs, however, in the interior of the milk, not merely at the surface, and the layer of pepsin is removed from the surface into the interior. This only shows that milk contains some substance which will re-form the enzyme, which may be a globular, soluble protein, very rapidly from a monolayer. The active constituent of pepsin is much more easily spread at a water-air surface than the inactive impurities in a commercial specimen indeed, the activity of many commercial pepsins may be greatly increased by spreading on water and transferring to a plate. [Pg.403]

Pepsin Obtained from the glandular layer of hog stomach. Produced as a white to light tan, water-soluble powder amber paste or clear, amber to brown, aqueous liquids. Major active principle pepsin. Typical applications used in the preparation of fishmeal and other protein hydrolysates and in the clotting of milk in manufacture of cheese (in combination with rennet). [Pg.147]


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See also in sourсe #XX -- [ Pg.88 ]




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