Ulf Lindahl

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.

The structures of xylosylserine and galactosylxylosylserine from heparin

Abstract Two carbohydrate-serine compounds from heparin have been further characterized. The structures of these substances, O-β- d -xylopyranosyl- l -serine and 4-O-β- d -galactopyranosyl -O-β- d -xylopyranosyl- l -serine , respectively, were found to be identical with those of xylosylserine and galactosylxylosylserine from chondroitin 4-sulfate. These findings conclusively establish that the heparin-protein linkage is a xylosidic bond involving the hydroxyl group of serine.

Biosynthesis of Heparin: Tritium Incorporation into Chemically Modified Heparin Catalyzed by C-5-Uronosylepimerase

Publisher Summary The epimerization of D-glucuronic to L-iduronic acid residues in the course of heparin biosynthesis is accompanied by the exchange of C-5 hydrogen atom. This feature of the reaction serves as the basis for an assay of epimerase activity, in which the release of tritium into the water of the incubation medium is measured with a D-[5-3H]glucosyluronic acid-labeled precursor polysaccharide as a substrate. This chapter discusses an experiment to study the enzymatic incorporation of radioactivity from T2O into chemically modified heparin, yielding a product suitable as a substrate in the epimerase assay. In the assay, heparin from hog mucosa was purified by repeated precipitation with cetylpyridinium chloride from 1.4 M NaCl essentially. The chapter illustrates the result by a graph providing the time course of tritium incorporation into modified heparin.