3-O-alpha-D-mannopyranosyl-alpha-D-mannopyranose xylosylphosphotransferase (, XPT1) is an enzyme with systematic name UDP-D-xylose:3-O-alpha-D-mannopyranosyl-alpha-D-mannopyranose xylosylphosphotransferase. This enzyme catalyses the following chemical reaction
Mn<sup>2+</sup> required for activity.