The co-polymeric structure of pig skin dermatan sulphate. Distribution of L-iduronic acid sulphate residues in co-polymeric chains.
1. Pig skin dermatan sulphate was degraded by periodate oxidation followed by alkaline elimination or by chondroitinase-ABC to quantify irregular repeating units, i.e. those containing D-GlcUA (D-glucuronic acid) and L-IdUA-SO4 (sulphated iduronic acid). 2. Previous results of periodate oxidation (Fransson, 1974) indicated repeating sequences in pig skin dermatan sulphate containing, on average, 3D-GlcUA, 9 L-IdUA-SO4 or 28 L-IdUA units in addition to N-acetylgalactosamine sulphate. However, complete digestion with chondroitinase-ABC yielded, at the most, 3-4 disulphated disaccharides/chain. Consequently, more than one-half of the L-IdUA-SO4 residues were present in monosulphated periods, i.e. IdUA-(SO4)-GalNAc. 3. To determine the location of L-IdUA-SO4 residues along the copolymeric chain dermatan sulphate was digested with testicular hyaluronidase. (This enzyme cleaves GalNAc-GlcUA bonds within block regions containing D-GlcUA.) By NaB3H4 reduction GalNAc residues located in the reducing end of the fragments were converted into [3H]GalNAcOH (N-acetylgalactosaminitol). Finally, the radioactive product was fragmented by periodate oxidation followed by alkaline elimination. The bulk of the radioactivity was associated with periodate-resistant oligosaccharides indicating that clusters of GlcUA-GalNAc-SO4 periods are often adjacent to a varying number of (n = 1-4) of L-IdUA-SO4-containing periods. 4. To study the distribution of L-IdUA-SO4-containing periods in relation to blocks of IdUA-GalNAc-SO4 periods different fractions of hyaluronidase-degraded dermatan sulphate were degraded separately. In all types of fragments (mol. wts. 1,500-10,000) L-IdUA-SO4-containing periods were demonstrated. In short fragments reducing terminal GalNAc-6-SO4 (6-sulphated N-acetylgalactosamine) was found confirming that these sequences were joined to relatively long D-GlcUA-containing block sequences via GalNAc-6-SO4. Moreover, low-molecular-weight oligosaccharides composed of alternating sequences were encountered. An octasaccharide derived from the carbohydrate sequence -GalNAc---GlcUA-GalNAc-IdUA-GalNAc-GlcUA-GalNAc-IdUA-GalNAc---GlcUA-GalNAc (--- indicates the position of cleavage by hyaluronidase) was identified.
D000818:Animals; D002807:Chondroitin / Q000031:analogs & derivatives*; D003871:Dermatan Sulfate / Q000032:analysis*; D005965:Glucuronates / Q000032:analysis; D006821:Hyaluronoglucosaminidase; D007067:Iduronic Acid / Q000032:analysis*; D008190:Lyases; D008970:Molecular Weight; D009844:Oligosaccharides / Q000032:analysis; D010084:Oxidation-Reduction; D012867:Skin / Q000032:analysis; D013429:Sulfatases; D013431:Sulfates / Q000032:analysis; D013552:Swine; D014574:Uronic Acids / Q000032:analysis*
D005965:Glucuronates; D009844:Oligosaccharides; D013431:Sulfates; D014574:Uronic Acids; D003871:Dermatan Sulfate; D007067:Iduronic Acid; D002807:Chondroitin; D013429:Sulfatases; D006821:Hyaluronoglucosaminidase; D008190:Lyases