Glycosylation pattern of human inter-alpha-inhibitor heavy chains

Biochem J. 1998 Aug 1;333 ( Pt 3)(Pt 3):749-56. doi: 10.1042/bj3330749.


Human inter-alpha-inhibitor (IalphaI) is a plasma serine-proteinase inhibitor. It consists of three polypeptide chains covalently linked by a glycosaminoglycan chain: a light chain named bikunin carrying the anti-proteinase activity and two heavy chains, H1 and H2, which exhibit specific properties, e.g. they interact with hyaluronan thus stabilizing the extracellular matrix. In this study, using matrix-assisted laser desorption ionization-time-of-flight MS and amino acid sequencing of tryptic peptides, we provide a detailed analysis of the glycosylation pattern of both heavy chains. H1 carries two complex-type N-glycans of predominantly biantennary structure linked to asparagine residues at positions 256 and 559 respectively. In contrast, the oligosaccharides attached to H2 are a complex-type N-glycan in the N-terminal region of the protein (Asn64) and three to four type-1 core-structure O-glycans mono- or di-sialylated, clustered in the C-terminal region. We propose that these O-glycans might function as a recognition signal for the H2 heavy chain. The biological implications of this hypothesis, notably for the biosynthetic pathway of IalphaI, are discussed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alpha-Globulins / chemistry
  • Alpha-Globulins / metabolism*
  • Amino Acid Sequence
  • Carbohydrate Sequence
  • Chromatography, High Pressure Liquid
  • Glycopeptides / chemistry
  • Glycopeptides / metabolism
  • Glycosylation
  • Humans
  • Macromolecular Substances
  • Molecular Sequence Data
  • Serine Proteinase Inhibitors / chemistry
  • Serine Proteinase Inhibitors / metabolism*
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization


  • Alpha-Globulins
  • Glycopeptides
  • Macromolecular Substances
  • Serine Proteinase Inhibitors
  • inter-alpha-inhibitor