Biological Functions of Xylose 2-O-Phosphorylation and Dephosphorylation in the Glycosaminoglycan-Linkage Region Tetrasaccharide

Abstract

Glycosaminoglycans (GAGs) are linear polysaccharide chains covalently attached to core proteins to form proteoglycans (PGs). GAG chain assembly begins with the synthesis of the common protein linkage region tetrasaccharide attached to the serine residues of specific core proteins. Previous structural analyses have shown that the GAG-protein linkage region tetrasaccharide of PGs is transiently modified by xylose 2-O-phosphorylation. We previously identified a Xyl kinase that phosphorylates C-2 of the xylose residue and phosphoxylose phosphatase. This review presents recent advances in the biological significance of phosphorylation and dephosphorylation of the Xyl residues in the linkage region tetrasaccharide of PGs.