Possible multifunctional enzyme with both glycosyltransferase and deubiquitinase activities. May be involved in protein N-glycosylation, second step of the dolichol-linked oligosaccharide pathway (By. similarity). N-acetyl-alpha-D-glucosaminyl-diphosphodolichol + UDP-N-acetyl-alpha-D-glucosamine = H(+) + N,N'-diacetylchitobiosyl diphosphodolichol + UDP Thiol-dependent hydrolysis of ester, thioester, amide, peptide and isopeptide bonds formed by the C-terminal Gly of ubiquitin (a 76-residue protein attached to proteins as an intracellular targeting signal). Isoform 2 may interact with ALG14. Could be recruited to the cytosolic face of the endoplasmic reticulum membrane through its interaction with ALG14. Belongs to the glycosyltransferase 28 family.