ALG13 is a 1,137 amino acid protein belonging to the glycosyltransferase 28 family. Encoded by a gene that maps to human chromosome Xq23, ALG13 is a subunit of a bipartite UDP-N-acetylglucosamine transferase and plays a role in protein folding regulation and stabilization. ALG13 contains one OTU domain, one TudorSN domain, and exists as four alternatively spliced isoforms. Heterodimerizing with ALG14, ALG13 forms a UDP-GlcNAc glycosyltransferase, which catalyzes the second sugar addition of the oligosaccharide precursor in endoplasmic reticulum (ER) N-linked glycosylation. ALG13 localizes to ER and may be recruited to the cytosolic face of the membrane by interacting with ALG14.