Glycosaminoglycan xylosylkinase (FAM20B)

Responsible for the 2-O-phosphorylation of xylose in the glycosaminoglycan-protein linkage region of proteoglycans thereby regulating the quantity of older GAG chains. Sulfated glycosaminoglycans (GAGs), such as heparan sulfate and chondroitin sulfate, are synthesized on the so-called common GAG- protein linkage region (GlcUAbeta1-3Galbeta1-3Galbeta1-4Xylbeta1- O-Ser) of core proteins, which is formed by the stepwise addition of monosaccharide residues by the respective specific glycosyltransferases.

Xylose 2-O-phosphorylation may influence the catalytic activity of B3GAT3 (GlcAT-I) which completes the precursor tetrasaccharide of GAG-protein linkage areas where the repeating disaccharide region is synthesized. .