Title: Casein
CAS Registry Number: 9000-71-9
Literature 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 a-, b-, g- and K-caseins, in order of decreasing mobility at pH 7. The complete amino acid sequence of bovine b-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 Type: 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.
Therap-Cat: Nutrient.

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