Recognizes glycoproteins with minor folding defects (PubMed:22960071). Reglucosylates single N-glycans near the misfolded part of the protein, thus providing quality control for protein folding in the endoplasmic reticulum (PubMed:22960071). Reglucosylated proteins are recognized by calreticulin for recycling to the endoplasmic reticulum and refolding or degradation (PubMed:11535823). N(4)-(alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc)-L-asparaginyl-[protein] (N-glucan mannose isomer 9A1,2,3B1,2,3) + UDP-alpha-D-glucose = H(+) + N(4)-(alpha-D-Glc-(1->3)-alpha-D-Man-(1->2)-alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->3)-[alpha-D-Man-(1->2)-alpha-D-Man-(1->6)]-alpha-D-Man-(1->6)]-beta-D-Man-(1->4)-beta-D-GlcNAc-(1->4)-alpha-D-GlcNAc)-L-asparaginyl-[protein] + UDP Protein modification; protein glycosylation. Monomer (PubMed:28490633). May interact with CG7484/Sep15 (Probable). Expressed in salivary glands (at protein level) (PubMed:11535823). Is present at low but detectable levels in the earliest embryos, increasing at 6-8 hours with a maximum at 10-12 hours (PubMed:7729408). Levels decrease thereafter and are not detected in 18-20 hours embryos and first instar larvae but is detected again at second instar to pupation (PubMed:7729408). Belongs to the glycosyltransferase 8 family.