High Quality Content by WIKIPEDIA articles! UGGT, or (UDP)-glucose:glycoprotein glucosyltransferase (160kDa) is a soluble enzyme resident in the lumen of the endoplasmic reticulum (ER). The main function of UGGT is to recognize misfolded glycoproteins and transfer a glucose (Glc) monomer (monoglucosylate) to the terminal mannose on the glycoprotein. It uses UDP-Glc as the glycosyl donor and requires calcium ions for its activity.