In enzymology, a xylosylprotein 4-beta-galactosyltransferase (EC 2.4.1.133) is an enzyme that catalyzes the chemical reaction
- UDP-galactose + O-beta-D-xylosylprotein UDP + 4-beta-D-galactosyl-O-beta-D-xylosylprotein
Thus, the two substrates of this enzyme are UDP-galactose and O-beta-D-xylosylprotein, whereas its two products are UDP and 4-beta-D-galactosyl-O-beta-D-xylosylprotein.
This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is UDP-galactose:O-beta-D-xylosylprotein 4-beta-D-galactosyltransferase. Other names in common use include UDP-D-galactose:D-xylose galactosyltransferase, UDP-D-galactose:xylose galactosyltransferase, galactosyltransferase I, and uridine diphosphogalactose-xylose galactosyltransferase. This enzyme participates in chondroitin sulfate biosynthesis and glycan structures - biosynthesis 1. It employs one cofactor, manganese.