The chemical structure of the main sugar moiety isolated from bovine whole casein.

Abstract

The sugar sequence of the main carbohydrate portion of bovine whole casein was investigated. A major trisaccharide consisting of N-acetylneuraminic acid, D-galactose and N-acetylgalactosaminitol in the molar ratio of 1:1:1 was obtained by alkali treatment of glycopeptide, which was isolated by enzymic digestion of caseinoglycopeptide from chymosin-treated casein. The trisaccharide and the glycopeptide were subjected to methylation and gas chromatographic analysis. On the basis of the analytical data and other data obtained from enzymic examination, the chemical structure of the main sugar portion isolated from bovine whole casein was identified to be N-acetylneuraminyl-α-2→3-galactosyl-β-1→3-N-acetylgalactosaminyl-X (threonine or serine).