Carbohydrate‐peptide Linkages in Glycoproteins and Mucopolysaccharides From Brain

Treatment of glycopeptides, prepared from glycoproteins of rat and rabbit brain, with NaOH‐NaBH4 leads to the destruction of a portion of the serine, threonine and galactosamine present, and the appearance in acid hydrolysates of alanine, α‐aminobutyric acid and galactosaminitol. These results indicate that N‐acetylgalactosamine at the reducing end of oligosaccharide chains in brain glycoproteins is linked O‐glycosidically to the hydroxyl groups of serine and threonine residues. 2‐acetamido‐1‐(L‐β‐aspartamido)‐l,2‐dideoxy‐β‐D‐glucose was also detected after partial acid hydrolysis of the alkali‐stable glycopeptides, and most of the carbohydrate in brain glycoproteins appears to be linked by N‐acetylglucosaminylasparagine linkages. The results of the treatment of the sulphated mucopolysaccharides from bovine brain with alkaline‐borohydride indicate that the polysaccharide chains in chondroitin sulphate and heparan sulphate are linked exclusively to serine.