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Isolation and analysis of kappa-casein glycomacropeptide from goat sweet whey
Eryck R Silva-Hernandez1, Takuo Nakano, Lech Ozimek
1Alberta Dairy Association Research Unit, Department of Agricultural, Food and Nutritional Science, 410 Agriculture/Forestry Center, University of Alberta, Edmonton, Alberta T6G 2P5, Canada. eryck@ualberta.ca
Abstract:
Glycomacropeptide (GMP) was purified from goat sweet whey by anion-exchange and hydrophobic interaction chromatography. Approximately 0.06% (w/v) of sweet whey was recovered as GMP. Amino acid analysis of the GMP preparation showed that the content of phenylalanine (an amino acid that does not occur in goat GMP) was negligible, indicating that the GMP was of high purity. The goat GMP contained 25 microg sialic acid per mg of dry weight. This was approximately 3-fold lower than the sialic acid concentration in bovine GMP reported in the literature. Gel electrophoretic results demonstrated that most of the goat GMP occurs as a dimer. The GMP was intensely stained with Coomassie blue in 50% methanol containing 12.5% (w/v) trichloroacetic acid, but showed very weak metachromasia with the same dye in 45% methanol containing 10% acetic acid, a preparation commonly used to stain protein.