Enzyme overexpression - an exercise toward understanding regulation of heparan sulfate biosynthesis

Sci Rep. 2016 Aug 11:6:31242. doi: 10.1038/srep31242.


Biosynthesis of heparan sulfate (HS) involves conversion of D-glucuronic acid (GlcA) to L-iduronic acid (IdoA) units catalyzed by glucuronyl C5-epimerase (Hsepi). IdoA units are the favored substrate for 2-O-sulfotransferase (2OST). We used HEK293 cells as a model to investigate the effects of overexpression of these enzymes on HS structure. Overexpression of Hsepi alone resulted in an unexpected increase in HS chain length. A Hsepi point-mutant (Y168A), devoid of catalytic activity, failed to affect chain length. Moreover, the effect of Hsepi overexpression on HS chain length was abolished by simultaneous overexpression of 2OST. These findings raise novel aspects on regulation of HS biosynthesis. We propose a hypothetical enzyme-binding protein (EBP) with distinct, specific and partly overlapping binding sites, the interactions of which will determine levels of enzymes available to the biosynthetic process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Carbohydrate Epimerases / genetics
  • Carbohydrate Epimerases / metabolism*
  • Catalysis
  • Glucuronic Acid / chemistry
  • HEK293 Cells
  • Heparitin Sulfate / biosynthesis*
  • Heparitin Sulfate / chemistry*
  • Humans
  • Iduronic Acid / chemistry
  • Mutation
  • Protein Binding
  • Sulfotransferases / metabolism*


  • Iduronic Acid
  • Glucuronic Acid
  • Heparitin Sulfate
  • Sulfotransferases
  • UST protein, human
  • Carbohydrate Epimerases
  • GLCE protein, human