The linkage of heparin to protein

Abstract The presence of residual amino acids in heparin isolated under mild conditions (Lindahl et al ., 1964) suggests that heparin may exist in the native state as a covalently-linked complex with protein. In certain heparin preparations, serine was the only amino acid found In significant amounts. Since chondroitin 4-sulfate is linked to protein through serine ( Muir, 1958; ; Roden et al ., 1963 ; Gregory et al ., 1964), these findings indicate that both polysaccharides are bound to protein in a similar manner. That heparin (Lindahl and Roden, 1964), as well as glycopeptides isolated from the chondroitin 4-sulfate-protein complex (Gregory et al ., 1964), contains galactose and xylose, indicates that these sugars may be involved in the carbohydrate-protein linkage. In order to gain more information concerning the nature of this linkage, attempts were made to obtain carbohydrate-serine compounds from heparin by mild acid hydrolysis. This communication describes the results of these experiments.