Caseins K-casein

Casein may be coagulated and recovered as rennet casein by treatment of milk with selected proteinases (rennets). However, one of the caseins, K-casein, is hydrolysed during renneting and therefore the properties of rennet casein differ fundamentally from those of acid casein. Rennet casein, which contains the colloidal calcium phosphate of milk, is insoluble in water at pH 7 but can be dissolved by adding calcium sequestering agents, usually citrates or polyphosphates. It has desirable functional properties for certain food applications, e.g. in the production of cheese analogues. 

Calpis Sour milk (3-casein, K-casein, Val-Pro-Pro, Ile-Pro-Pro Reduction of blood pressure Calpis Co., Japan Hata et al. (1996) Takano (2002)... 

For example, a - casein contains one major subfraction (a -Cn) plus several minor components. The four genetic variantssof < si-casein have similar isoionic points, which would be expected from their similar primary structures. The 3-caseins, K-caseins, and "whole -caseins" have also been fractionated and their subfractions characterized (Table 1). The isoionic points for all of these casein subunits range from about 4.9 to 6.0 and their molecular weights range from about 11,500 to 24,000. 

In contrast with a i- and jS-caseins, the presence of systein residues in as2- and K-caseins leads to the formation of disulphide bonds. The number of molecules that bond to each other in K-casein differs from that in as2-casein. That is to say that in K-casein not less than 10 molecules join each other via disulphide linkages, while in most of as2-caseins only 2 molecules are linked by disulphide bonds and form a dimer. As well, intermolecular disulfide bonds have been reported for as2- and K-caseins [6, 11]. The joint of two classes of caseins for instance as2-casein-K-casein, has also been reported [6] due mainly to the different charges of C-terminal regions in these two molecules [8]. 

Kumosinski, T.E., Brown, E.M., Farrell, H.M. Three-dimensional molecular modeling of bovine caseins K-casein. J. Dairy Sd. 74, 2879-2887 (1991)... 

Kase-lab, n. rennet, -leim, m. casein glue, k sen, v.i. curd, curdle. 

ANASTASIA J V, BRAUN B L and SMITH K T (1990) General and histopathological results of a two-year study of rats fed semi-purified diets containing casein and soya protein. Food Chem Toxicol. 28 (3) 147-56. 

Casein refers to a family of proteins, namely, ttgi-, 0. 2-, p-, and k-caseins (Table 5.1). Digestion of a- and p-caseins leads to production of peptides that may bind to opioid receptors that exist in the nervous, endocrine, immime, or gastrointestinal system (Kampa et ah, 1996 Meisel, 2004). These compoimds may modulate absorption processes in the gut and can potentially affect gastrointestinal fimction through transit... 

Helstad, K. M., Bream, A. D., Trckova, J., Paulsson, M., and Dejmek, P. (2005). Nano-heological properties of casein. In "Food Colloids Interactions, Microstructure and Processing", (E. Dickinson, Ed.), pp. 218-229. The Royal Society of Chemistry, Cambridge. 

The most abundant milk protein is casein, of which there are several different kinds, usually designated a-, (1-, and K-casein. The different caseins relate to small differences in their amino acid sequences. Casein micelles in milk have diameters less than 300 nm. Disruption of the casein micelles occurs during the preparation of cheese. Lactic acid increases the acidity of the milk until the micelles crosslink and a curd develops. The liquid portion, known as whey, containing water, lactose and some protein, is removed. Addition of the enzyme rennet (chymosin) speeds up the process by hydrolysing a specific peptide bond in K-casein. This opens up the casein and encourages further cross-linking. 

Greaves, K.A., Parks, J.S., Williams, J.K. and Wagner, J.D. (1999). Intact dietary soy protein, but not adding an isoflavone-rich soy extract to casein, improves plasma lipids in ovariectomized cunomologus monkeys, J. Nutr., 129, 1585-1592. 

Tandy, P., Fares, K., Lorient, D., and Voilley, A. Effect of chemical modification of sodium caseinate on diffusivity of aroma compounds in aqueous solutions, / Agric. Food Chem., 45(7) 2649-2653, 1997. 

Kobayashi S, Koga K, Hayashida O, Nakano Y and Hasegawa Y (1990) Specific inhibition of insoluble glucan synthase (GTF-1) by Maillard reaction products from casein and albumins. Agric Biol Chem 54, 1417-1424. 

K. Kozco, A.D. Nikolov, D.T. Wasan, R.P Borwankar, and A. Gonsalves Layering of Sodium Caseinate Submicelles in Thin Liquid Films-A New Stability Mechanism... 

Lin JM, Kilman VL, Keegan K et al 2002 A role for casein kinase 2a in the Drosophila circadian clock. Nature 420 816-820... 

Lee C, Bae K, Edery I 1999 PER and TIM inhibit the DNA binding activity of a Drosophila CLOCK-CYC/dBMALl heterodimer without disrupting formation of the heterodimer a basis for circadian transcription. Mol Cell Biol 19 5316—5325 Lin JM, Kilman VL, Keegan K et al 2002a A role for casein kinase 2alpha in the Drosophila circadian clock. Nature 420 816—820... 

Ishida N, Miyazaki K, Sakai T 2001 Circadian rhythm biochemistry from protein degradation to sleep and mating. Biochem Biophys Res Commun 286 1—5 Kloss B, Price JL, Saez L et al 1998 The Drosophila clock gene double-time encodes a protein closely related to human casein kinase lepsilon. Cell 94 97—107 Lau LF, Nathans D 1987 Expression of a set of growth-related immediate early genes in BALE/ c 3T3 cells coordinate regulation with c-fos or c-myc. Proc Natl Acad Sci USA 84 1182-1186... 

Products of Limited K-Casein Proteolysis Book 2 XXI Intern. Dairy Congr. Moscow,1982, ppl61. 

Anal, A.K., Tobiassen, A., Flanagan, J., Singh, H. (2008). Preparation and characterization of nanoparticles formed by chitosan-caseinate interactions. Colloids and Surfaces B Biointerfaces, 64, 104-110. 

Portnaya, I., Cogan, U., Livney, Y.D., Ramon, O., Shimoni, K., Rosenberg, M., Danino, D. (2006). Micellization of bovine p-casein studied by isothermal titration microcalorimetry and cryogenic transmission electron microscopy. Journal of Agricultural and Food Chemistry, 54, 5555-5561. 

The casein responsible for colloidal stabilization of the casein micelle is K-casein. This glycoprotein has a molecular weight of 19 kDa and is composed of 169 amino acids (Swaisgood, 2003). K-Casein is special in being the only casein component that is insensitive to calcium ions (up to concentrations of 400 mM). 

Figure 6.1 The dual binding model of the structure of the casein micelle as built up from the individual caseins (0 1, o 2, P and k) in combination with calcium phosphate (CaP). Reproduced from Home (1998) with permission.

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