Lactoglobulins

Casein. Milk contains proteins and essential amino acids lacking in many other foods. Casein is the principal protein in the skimmed milk (nonfat) portion of milk (3—4% of the weight). After it is removed from the Hquid portion of milk, whey remains. Whey can be denatured by heat treatment of 85°C for 15 minutes. Various protein fractions are identified as a-, P-, and y-casein, and 5-lactoglobulin and blood—semm albumin, each having specific characteristics for various uses. Table 21 gives the concentration and composition of milk proteins. 

Godovac-Zimmerman, J. The structural motif of p-lactoglobulin and retinol-binding protein a basic framework for binding and transport of small hydrophobic molecules Trends Biochem. Sci. 

Papiz, M.Z., et al. The structure of p-lactoglobulin and its similarity to plasma retinol-binding protein. Nature 324 383-385, 1986. 

The proteolytic digestion of j6-lactoglobulin was carried out with trypsin which, as indicated in Table 5.4 above, is expected to cleave the polypeptide backbone at the carboxy-terminus side of lysine (K) and arginine (R). On this basis, and from the known sequence of the protein, nineteen peptide fragments would be expected, as shown in Table 5.7. Only 13 components were detected after HPLC separation and, of these, ten were chosen for further study, as shown in Table 5.8. 

Table 5.7 Theoretically predicted polypeptides from the trypsin digestion of S-lacto-globulin (/3LG) . Reprinted from J. Chromatogr., A, 763, Turula, V. E., Bishop, R. T., Ricker, R. D. and de Haseth, J. A., Complete structure elucidation of a globular protein by particle beam liquid chromatography-Fourier transform infrared spectrometry and electrospray liquid chromatography-mass spectrometry - Sequence and conformation of /3-lactoglobulin , 91-103, Copyright (1997), with permission from Elsevier Science...

Showing the monoisotopic masses of fragments MH+ of /i-lactoglobulin A cysteine residues are shown in bold script, i.e. cysteine-C aromatic residues are underlined, i.e. phenylalanine-F, tyrosine-F, and tryptophan- mIz expected for singly charged species. 

The influence of pH, ionic strength, and protein concentration on the extraction of a-lactalbumin and 3-lactoglobulin from an aqueous solution with water/AOT/isooctane microemulsions and their separation has been reported [168],... 

Milk Morinaga FASPEK Milk Western Blot Kit ( 3-lactoglobulin) Morinaga Inshtute of Biological Sciences Co. P-lactoglobulin 18,400... 

Gezimati, J., Creamer, L. K., and Singh, H. (1997). Heat-induced interactions and gelation of mixtures of p-lactoglobulin and a-lactalbumin. /. Agric. Food Chem. 45,1130-1136. 

Kontopidis, G., Holt, C., and Sawyer, L. (2004). Invited review Beta-lactoglobulin Binding properties, structure, and function. /. Dairy Sci. 87, 785-796. 

Kuwata, K., Shastry, R., Cheng, H., Hoshino, M., Batt, C. A., Goto, Y., and Roder, H. (2001). Structural and kinetic characterization of early folding events in beta-lactoglobulin. Nat. 

Mousavi, S. H., Bordbar, A. K., and Haertle, T. (2008). Changes in structure and in interactions of heat-treated bovine beta-lactoglobulin. Protein Pept. Lett. 15, 818-825. 

Skim milk (35 g/L) and /1-lactoglobulin (5 g/L) solutions were prepared by dissolving skim milk powder and y6-lactoglobulin powder in distilled water and stirring at room temperature for 4 h. /1-Casein (5 g/L) had been hydrated in a phosphate buffer (100 mM, pH 8) and stirred at 4°C for one night [27]. Sodium azide (0.1%, wt/v) was added to prevent bacterial growth. 

Four reconstituted milks were prepared by blending hydrated skim milk powder (35g/L) with four different emulsions (35g/L) differing by composition of the fat-water interface. Whole reconstituted milks were coded MP (milk proteins), BCAS ( 6-casein), and BLG5 (j6-lactoglobulin 5 g/L). 

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