Proteose peptone

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. 

Total nitrogen = Kjeldahl I Proteose peptone N = Kjeldahl IV- Kjeldahl m... 

Isolated as2-casein in solution is also very susceptible to plasmin eight peptide bonds are hydrolysed with the production of 14 peptides. Plasmin also hydrolyses as2-casein in milk but the peptides formed have not been identified, although at least some are included in the proteose-peptone fraction. 

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. 1981. Identification of proteose-peptone component 5 as a plasmin derived fragment of /3-casein. Int. J. Biochem. 13, 1081-1086. 

Kanno, C. and Yamauchi, K. 1979. Relationship of soluble glycoprotein of milk fat globule to components -3, -5, and -8 of proteose peptone. Agr. Biol. Chem. 43, 2105-2113. 

Kolar, C. K. and Brunner, J. R. 1969. Proteose-peptone fraction of bovine milk Distribution in protein system. J. Dairy Sci. 52, 1541-1546. 

Pancreatic and malt amylases gradually lose their activity in the aqueous dispersions in which they act. As above noted, there is good evidence that this is due to a destructive hydrolysis of the enzyme. The destructive action of water upon enzyme is less pronounced in the presence of substrate, probably because the combination of enzyme with substrate serves to some extent to protect the enzyme from hydrolysis. It is less rapid in solutions of commercial pancreatin and in water extracts of malt than it is in solutions of purified pancreatic and malt amylases, doubtless because of the presence in the former of substances which are products of protein hydrolysis (proteoses, peptones, polypeptids, amino acids) and whose presence therefore tends to retard further protein hydrolysis and thus to protect the enzyme protein from hydrolytic destruction, or at least to diminish the rate at which such deterioration of the enzyme occurs. 

The y-casein fractions and proteose peptone fractions 5, 8-slow, and 8-fast have amino acid sequences corresponding to parts of the sequence of p-casein (Fig. 1). Their occurrence in milk could be due to partial gene duplication but identical fractions can be produced... 

Hasegawa A, Yamashita H, Kondo S, Kiyota T, Hayashi H, Yoshizaki H, Murakami A, Shiratsuchi M, Mori T (1988), Proteose peptone enhances production of tissue-type plasminogen activator from human diploid fibroblasts, Biochem. Biophys. Res. Commun. 150 1230-1236. 

Pro-oxidant conditions are favoured in infant formulae by the presence of iron and of vitamin C and can lead to oxidative damage to tryptophan residues, which here is of particular importance, tryptophan often being the limiting amino acid. Using a-lactalbumin as a model compound, as it is high in tryptophan, Puscasu and Birlouez-Aragon484 studied the loss of fluorescence due to tryptophan (Aex=290/Aem=340 nm) on incubation with lactose, preformed early and advanced MRP (from proteose-peptone, because it is low in tryptophan), H202/Fe2+, or ascorbate/Fe3+. In each case, after 3 h, there was an appreciable loss of tryptophan from the pH 4.6-soluble protein of about 28%. The MRPs, both formed and preformed, exhibited fluorescence at Aex = 350/Aem = 435-440 (major) and Aex = 330/Aem = 420 nm. 

Proteose-peptones NA 1.2 Potential mineral carrier Walstra et al. (1999)... 

TIM Small intestine Oral cavity mucin, cellobiose, proteose peptone, starch), pH 5.2 Pancreatic fluid (bovine bile, pancreatine), pH 6.5 Saliva, pH 5 Pb As, Cd, 5, 14... 

C-Methyl-/3-Casein. 14C-Labeled proteins prepared by reductive methylation have potential as substrates in the study of proteolytic enzymes. A serious limitation is that complete methylation of lysine residues results in inhibition of proteolysis by enzymes with trypsin-like specificity (13). It was interesting to determine whether this problem could be overcome by incomplete methylation which left unaltered most of the lysine residues in more or less random distribution throughout the protein. /3-Casein was selected as a suitable protein for this study since it is cleaved by trypsin-like enzymes to well characterized fragments, the y-caseins, in addition to less well characterized fragments, the proteose peptones. We anticipated that this type of study could provide a basis for a general investigation of milk protein transformation by the native milk proteinase which has a specificity similar to trypsin (14). 

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