The sulphated carbohydrate-protein linkage region isolated from chondroitin 4-sulphate chains of inter-α-trypsin inhibitor in human plasma

• Published in: Glycobiology (Oxford) 1995-05, Vol.5 (3), p.335-341
• Main Authors: Yamada, Shuhei, Oyama, Mika, Kinugasa, Hitoko, Nakagawa, Tomoyo, Kawasaki, Toshisuke, Nagasawa, Shigeharu, Khoo, Kay-Hooi, Morris, Howard R., Dell, Anne, Sugahara, Kazuyuki
• Format: Article
• Language: English
• Subjects: Alpha-Globulins - chemistry; Amino Acid Sequence; Carbohydrate Sequence; Carbohydrates - chemistry; Carbohydrates - isolation & purification; Chondroitin Sulfates - chemistry; chondroitin sulphate; FAB-MS; Glycopeptides - chemistry; Humans; inter-α-trypsin inhibitor; Molecular Sequence Data; Proteins - chemistry; Proteins - isolation & purification; Spectrometry, Mass, Fast Atom Bombardment; sulphated oligosaccharides; Trypsin Inhibitors - chemistry
• ISSN: 0959-6658; 1460-2423
• DOI: 10.1093/glycob/5.3.335

Inter-α-trypsin inhibitor (ITI) in human plasma has a unique structural architecture composed of three polypeptide chains (H1, H2 and L chains), which are linked to each other through a chondroitin 4-sulphate chain. The structure of the carbohydrate-protein linkage region of the chondroitin 4-sulphate chain attached to the L chain was investigated. The peptide-chondroitin sulphate fraction was isolated by anion-exchange chromatography after exhaustive digestion with lysyl endopeptidase and then V8 protease. The chondroitin 4-sulphate chain was released from the peptides by β-elimination using NaB3H4, and then digested with chondroitinase ABC. These treatments resulted In a single 3H-labelled hexasaccharide alditol fraction derived from the linkage region which had been associated with the L chain. Chemical and enzymatic analyses as well as fast-atom bombardment-mass spectrometry (FAB-MS) analysis revealed that the 3H-labelled hexasaccharide alditol had the following structure:δHexAα1-3GalNAc(4-sulphate)β1-4GlcAβ1-3Gal(4-sulphate)β1-3Galβ1-4Xyl-ol (where ΔHexA is 4-deoxy-α-L-threo-hex-4-enepyranosyluronic acid and Xyl-ol is xylitol). The structure contained the novel 4-sulphated Gal residue, which was previously demonstrated in a linkage hexasaccharide isolated from chondroitin 4-sulphate of rat chondrosarcoma (Sugahara et al., J. Biol Chem., 263,10168–10174, 1988) and of whale cartilage (Sugahara et al., Eur. J. Biochem., 202, 805–811, 1991). The above disulphated hexasaccharide alditol was the only component detected in the linkage region fraction of the chondroitin 4-sulphate chain of ITI, which implies some biological significance of this novel structure.