This eukaryotic enzyme performs the final step in the synthesis of the lipid-linked oligosaccharide, attaching D-glucose in an ¦Á-1,2-linkage to the outermost D-glucose in the long branch. The lipid-linked oligosaccharide is involved in N-linked protein glycosylation of selected asparagine residues of nascent polypeptide chains in eukaryotic cells.