Interaction between dermatan sulphate chains II. Structural studies on aggregating glycan chains and oligosaccharides with affinity for dermatan sulphate-substituted agarose

Abstract

1. 1. The chemical structure of aggregating and non-aggregating dermatan sulphate phate from pig skin and beef and human aorta has been examined. Aggregating chains were subjected to various enzymic and chemical degradations prior to affinity chromatography on dermatan sulphate-substituted agarose. After cleavage of glucoronic acid-containing block regions by testicular hyaluronidase a small amount of material was still bound. Cleavage of all bonds between glucuronic acid and hexosamine by chondroitinase-AC abolished binding to the ligand. Periodate oxidation of non-sulphated iduronic acid residues followed by cleavage in alkali markedly reduced binding to the gel. 2. 2. Analyses of oligosaccharides obtained by periodate oxidation-alkaline elimination showed that aggregating species contained larger amounts of single glucuronic acid- N-acetylgalactosamine- O-sulphate periods surrounded by iduronic acid-containing units than did non-aggregating species. 3. 3. Degradation with testicular hyaluronidase of aggregating chains afforded larger quantities of hexa-, octa- and decasaccharides than did degradations of non-aggregating chains. Oligosaccharides releasedfrom aggregating glycans by this enzyme were further degraded by chondroitinase-AC into tetrasaccharides with iduronic acid in the internal position. Thus, alternating sequences were present in aggregating chains but very rare in non-aggregating ones. 4. 4. Oligosaccharides obtained by hyaluronidase degradation of aggregating dermatan sulphate were subjected to affinity chromatography on dermatan sulphate-substituted gel. Fractions that contained oligosaccharides of decasaccharide size or larger and with alternating sequences were partially bound to the ligand. Oligosaccharides without these structural features (derived from non-aggregating chains or from chondroitin 4-sulphate) showed no binding. Oligosaccharides derived from aggregating chains via periodate oxidation-alkaline elimination were not bound to the dermatan sulphate ligand. 5. 5. It is proposed that the contact regions of aggregating dermatan sulphate chains contain the following sequences: ▪