The glycan code of the endoplasmic reticulum: asparagine-linked carbohydrates as protein maturation and quality-control tags

Trends Cell Biol. 2005 Jul;15(7):364-70. doi: 10.1016/j.tcb.2005.05.007.


The majority of proteins that traverse the secretory pathway receive asparagine (Asn)-linked glycosylations. Glycans are bulky hydrophilic modifications that serve a variety of structural and functional roles within the cell. Here, we review the recent growing knowledge on the role of Asn-linked glycans as maturation and quality-control protein tags in the early secretory pathway. The carbohydrate composition encodes crucial information about the structure, localization and age of glycoproteins. The "glycan code" is encoded by a series of glycosidases and carbohydrate transferases that line the secretory pathway. This code is deciphered by carbohydrate-binding proteins that possess distinct carbohydrate binding properties and act as molecular chaperones or sorting receptors. These glycosidases and transferases work in concert with resident secretory pathway carbohydrate-binding proteins to form a network that assists in the maturation and trafficking of both native and aberrant glycoproteins within the cell.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Asparagine / chemistry
  • Asparagine / metabolism
  • Endoplasmic Reticulum / enzymology
  • Endoplasmic Reticulum / metabolism*
  • Glycoproteins / chemistry
  • Glycoproteins / metabolism*
  • Glycosylation
  • Humans
  • Membrane Proteins / metabolism
  • Molecular Chaperones / metabolism
  • Polysaccharides / chemistry
  • Polysaccharides / metabolism*
  • Protein Folding
  • Protein Processing, Post-Translational
  • Protein Transport


  • EDEM1 protein, human
  • Glycoproteins
  • Membrane Proteins
  • Molecular Chaperones
  • Polysaccharides
  • Asparagine