Mannosyl Alpha-1,3-Glycoprotein Beta-1,4-N-Acetylglucosaminyltransferase (MGAT4)

MGAT4 encodes a key glycosyltransferase that regulates the formation of tri- and multiantennary branching structures in the Golgi apparatus. The encoded protein, in addition to the related isoenzyme B, catalyzes the transfer of N-acetylglucosamine (GlcNAc) from UDP-GlcNAc in a beta-1,4 linkage to the Man-alpha-1,3-Man-beta-1,4-GlcNAc arm of R-Man-alpha-1,6(GlcNAc-beta-1,2-Man-alpha-1,3)Man-beta-1, 4-GlcNAc-beta-1,4-GlcNAc-beta-1-Asn. The encoded protein may play a role in regulating the availability of serum glycoproteins, oncogenesis, and differentiation. The predicted 535-amino acid MGAT4A protein is a type II membrane protein, similar to other known Golgi glycosyltransferases. MGAT4A has 3 potential N-glycosylation sites. Human MGAT4A and bovine GnT-IV share 96% amino acid sequence identity.