3-O-alpha-D-mannopyranosyl-alpha-D-mannopyranose xylosylphosphotransferase (EC2.7.8.32, XPT1) is an enzyme with systematic nameUDP-D-xylose:3-O-alpha-D-mannopyranosyl-alpha-D-mannopyranose xylosylphosphotransferase.[1] This enzyme catalyses the following chemical reaction