Proteoses and peptones

Add to 2 cc. of the solution 2 to 3 drops of 0.5 per cent solution of acetic acid and boil. Are the proteins coagulated  

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The so-called "trypsin," obtainable from pancreatic juice and from fresh extracts of the pancreas, is not a simple enzyme but a mixture of trypsin proper (which hydrolyses proteins to proteoses and peptones) and a series of enzymes which hydrolyse these breakdown products to their constituent amino-acids. The term trypsin," when used below, refers to this mixture. 

In this compound we have a substance approaching the proteins in complexity and it has been found to resemble the proteins and the proteoses and peptones in its physical properties. Furthermore, a simpler synthetic poly-peptide, viz., a tetra-peptide has been found to be almost identical with an isomeric poly-peptide obtained by the hydrolysis of a silk protein. This synthetic tetra-peptide has the following constitution ... 

Chymotrypsin is secreted from the pancreas in the zymogen form as chymotrypsinogen and it is converted to the active form by trypsin. It reacts with the substrates protein, proteoses and peptones cleaving the peptide bonds whose carboxyl groups are furnished by aromatic amino acids. 

The proteins insoluble in the cell-sap water are made soluble for translocation by means of proteolytic enzymes which change them into proteoses and peptones. 

Pepsin converts proteids into proteoses and peptones. 

The terms proteose and peptone refer to protein breakdown products of large polypeptides these differ from true proteins in that they are not coagulated by heat. A wide variety of peptides are formed when proteins are hydrolyzed in the digestive tract or in the laboratory. 

Proteins, according to Cohnheim, are not hydrolysed by erepsin, the enzyme of the intestinal mucous membrane, which hydrolyses only the proteoses and peptones, converting them into amino acids if proteins are previously hydrolysed by pepsin, they are then converted into amino acids by erepsin. Pepsin would therefore appear to have a special function rather than act like trypsin and the other enzymes, and it may attack one of the other possible linkings of amino acids. If it only produces some five or six products, there would only be the same number of such linkages. 

It is only by the knowledge of the properties of the synthetical compounds that Fischer has been able to invent methods for isolating them from the mixtures which result by the hydrolysis of the proteins and to identify these compounds. The extension of the study of the higher polypeptides, more especially of the mixed polypeptides, will lead without doubt to the isolation of greater complexes from the products of partial hydrolysis of the proteins, such as the separation of the proteoses and peptones, which from the results so far obtained appear to be more simple than was previously supposed, if salting out by ammonium sulphate of polypeptides containing four and six units, of which tyrosine is one, be taken as a typical example. 

CrnTTENDEN A. J. A. Hartweu. Crystalline globulin and gbbuloses or vitd-loses, Joum. of Physiol., 1890, p. 435. — The relative formation of proteoses and peptones in gastric digestion, Joum. of Physiol., 1891, p. 12. 

Chittenden a. G. L. Aueruan. A comparison of artificial and natural gastric digestion, together with a study of the diffusibility of proteoses and peptones, Joum. of Physiol., 1893, (14), P- 483-... 

This scheme of analysis is useful for the examination of artificial mixtures and peptic and tryptic digestion products. It does not differentiate between albumin and globulin or between proteose and peptone when present along with other higher and lower proteins. Such differentiation can be accomplished best by fractional precipitation with neutral salts, supplemented by the foregoing tests. 

In addition to the very large role that enzymes play in life processes and medicine and in industrial fermentation and related processes, enzymes are finding a growing role in industrial products, such as detergents, where enzymes tend to break down proteins to water-soluble proteoses nr peptones. Enzymes for such use must remain active at relatively high pH values (8.5 to 9.5) and remain stable for a long product shelf life. See also Detergents. 

As stated in 1953 (Gll) Dissolved mucoproteose is not a chemical entity, but a complex of intermediate products of digestion of gastric mucus. For this reason, the peptide moiety of this fraction may show transitions between the first and further split products of enzymatic degradation of proteins (proteans, primary and secondary proteoses, and even peptones). This is why one part of the mucoproteose fractions is dialyzable, and disappears from the electrophoretic partition of the dialyzed gastric juice. ... 

Proteinases catalyze the hydrolysis of peptide linkages in proteins. Those proteinases which have been purified have also been shown to have peptidase activity, that is, they catalyze the hydrolysis of synthetic polypeptides of known structure. Because the proteinases split proteins to yield lower molecular weight peptones, proteoses, and peptides they have been termed endopeptidases they are capable of hydrolyzing peptide bonds that are not terminal. Exopeptidases can hydrolyze only peptide bonds that involve terminal amino acids. The synthesis of peptide substrates has been authoritatively reviewed by Fruton. ... 

Nitrogen sources include proteins, such as casein, zein, lactalbumin protein hydrolyzates such proteoses, peptones, peptides, and commercially available materials, such as N-Z Amine which is understood to be a casein hydrolyzate also corn steep liquor, soybean meal, gluten, cottonseed meal, fish meal, meat extracts, stick liquor, liver cake, yeast extracts and distillers solubles amino acids, urea, ammonium and nitrate salts. Such inorganic elements as sodium, potassium, calcium and magnesium and chlorides, sulfates, phosphates and combinations of these anions and cations in the form of mineral salts may be advantageously used in the fermentation. 

About 20% of the total protein of bovine milk belongs to a group of proteins generally referred to as whey or serum proteins or non-casein nitrogen. Acid and rennet wheys also contain casein-derived peptides both contain proteose-peptones, produced by plasmin, mainly from /J-casein, and the latter also contains (glyco)macropeptides produced by rennets from K-casein. These peptides are excluded from the present discussion. 

Figure 9.14 The denaturation of the total ( ) and individual whey proteins in milk, heated at various temperatures for 30 min /l-lactoglobulin ( ), a-lactalbumin (O). proteose peptone ( ), immunoglobulins (A), and serum albumin ( ) (from Webb and Johnson, 1965).

Andrews, A. T. 1978A. The composition, structure, and origin of proteose-peptone component 5 of bovine milk. Eur. J. Biochem. 90, 59-65. 

Eigel, W. N. and Keenan, T. W. 1979. Identification of proteose-peptone component 8-slow as a plasmin-derived fragment of (3-casein. Int. J. Biochem. 10, 529-535. 

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