Studies on Casein. II. The Carbohydrate Moiety of Casein

Abstract

Summary The carbohydrate in casein has been estimated by hydrolysis of the protein with a mixture of dilute hydrochloric acid and a cation exchange resin, passage of the hydrolysate through a cation exchange column to remove interfering substances, and the measurement of the colour produced by the reaction of the liberated sugar with an anthrone reagent. The sugar contents of whole casein (Warner), alcohol-extracted casein, α -casein, β -casein, and γ -casein determined in this manner were approximately 3.8, 1.8, 1.5, 0.8, and 0.9 mg/g, respectively. The individual sugars in the casein preparations were determined quantitatively by filter paper chromatography. Whole casein contained galactose (1.84 mg/g), glucose (1.11 mg/g), and mannose (0.53 mg/g). Alcohol-extracted whole casein contained galactose (1.34 mg/g) and mannose (0.56 mg/g) and α -casein also contained galactose (0.75 mg/g) and mannose (0.48 mg/g). β -casein contained only galactose (0.52 mg/g) and γ -casein contained only galactose (0.48 mg/g).