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

Glycobiology. 1995 May;5(3):335-41. doi: 10.1093/glycob/5.3.335.

Abstract

Inter-alpha-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 beta-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: delta HexA-alpha 1-3GalNAc(4-sulphate)beta 1-4GlcA beta 1-3Gal(4-sulphate)beta 1-3Gal beta 1-4Xyl-ol (where delta HexA is 4-deoxy-alpha-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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alpha-Globulins / chemistry*
  • Amino Acid Sequence
  • Carbohydrate Sequence
  • Carbohydrates / chemistry
  • Carbohydrates / isolation & purification*
  • Chondroitin Sulfates / chemistry*
  • Glycopeptides / chemistry
  • Humans
  • Molecular Sequence Data
  • Proteins / chemistry
  • Proteins / isolation & purification*
  • Spectrometry, Mass, Fast Atom Bombardment
  • Trypsin Inhibitors / chemistry*

Substances

  • Alpha-Globulins
  • Carbohydrates
  • Glycopeptides
  • Proteins
  • Trypsin Inhibitors
  • inter-alpha-inhibitor
  • Chondroitin Sulfates