Emerging chemical and biochemical tools for studying 3- O -sulfated heparan sulfate.

Heparan sulfate is a widely expressed polysaccharide in the extracellular matrix and on the cell surface. 3- O -sulfated heparan sulfate represents only a small percentage of heparan sulfate from biological sources. However, this subpopulation is closely associated with biological functions of heparan sulfate. The 3- O -sulfated heparan sulfate is biosynthesized by heparan sulfate 3- O -sulfotransferase, which exists in seven different isoforms. This review article summarizes the recent progress in the substrate specificity studies of different 3- O -sulfotransferase isoforms involving the use of homogeneous oligosaccharide substrates and crystal structural analysis. The article also reviews a newly developed liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based method to analyze the level of 3- O -sulfated heparan sulfate with high sensitivity and quantitative capability. This newly emerged technology will provide new tools to study the structure and function relationship of heparan sulfate.