Nomenclature
CAS number: 9000-71-9
Description and references
A mixture of related phosphoproteins occurring
in milk and cheese. Present to the extent of 3% in bovine milk.
One of the most nutritive milk proteins in that it contains all of
the common amino acids and is rich in the essential ones. Produced
in mammary tissue from amino acids supplied by the blood. Obtained
from milk by removing the cream and acidifying the skimmed milk which
causes casein to precipitate. In cheese manufacture, casein is precipitated
by the lactic acid formed from the same milk by fermentation. Precipitation
by rennet is favored for casein intended for plastics manuf. Curdling
by electricity has been described. The prepn of pure casein is described
by Hammarsten, Textbook of Physiological Chemistry (New York, 7th ed., 1911) p 619; Abderhalden's
Handbuch vol. II (Berlin, 1910) p 384. Alternate
prepn: van Slyke, Baker, J. Biol. Chem. 35, 127 (1918); cf. Cohn, Hendry, Org. Synth. coll. vol. II, 120
(1943). Prepn of casein free from vitamin B12 for nutrition
experiments: Kissel, US 2853479 (1958 to Natl. Dairy Prods.). The major casein
components may be distinguished by electrophoresis and are designated
as α-, β-, γ- and K-caseins, in order of decreasing mobility
at pH 7. The complete amino acid sequence of bovine β-casein is known
and contains 209 residues with an approx. mol wt of 23,600: Ribadeaudumas et al., Eur. J. Biochem. 25, 505 (1972). Review: McKenzie, Adv. Protein Chem. 22, pp 75-135
(1967).
Properties
White, amorphous powder or granules without odor
or taste. Very sparingly sol in water and in nonpolar organic solvents;
sol in aqueous solns of alkalies, levorotatory. The isoelectric zone
is around pH 4.7; sol in concd HCl with light violet color. Amphoteric;
forms salts with both acids and bases. Present in bovine milk as
neutral calcium caseinate and in human milk as potassium caseinate.
Precipitated from solns satd with metallic salts. Forms a hard,
insol plastic with formaldehyde.Derivative
Casamino acids.
Properties
Commercial acid-hydrolyzed casein. Hydrolysis
is carried out until all the nitrogen in the casein is converted to
amino acids or other compounds of relative chemical simplicity. Prepn:
Mueller, Miller, J. Immunol. 40, 21 (1941); Mueller, Johnson, ibid. 33. Typical
analysis: N 10%, NaCl 14%, ash 20%, phosphorus as PO4 2%,
Fe 15 mg/3 g.Note
Legumin, also known as avenin or vegetable casein, occurring in beans and nuts, is a globulin resembling
casein. Isoln from Avena sativa L., Graminea: Sanson, Compt. Rend. 96, 75 (1883). Structure: C. J. Bailey, D. Boulter, Eur. J. Biochem. 17, 460 (1970).Use
In the manuf of molded plastics, adhesives, paints,
textile finishes, paper coatings, man-made fibers. Vitamin-free casein
is used in diets of animals employed for the biological assay of vitamins.
Medicinal grades are used in dietetic prepns and for determining
the effectiveness of digestive enzyme prepns contg. pepsin, trypsin,
papain. Casamino acids are used in microbial assays and in the prepn
of microbiological media.
Therapeutic Category
Nutrient.