Gene in humans
Alpha-1,3-mannosyl-glycoprotein 4-beta-N-acetylglucosaminyltransferase B is an enzyme that in humans is encoded by the MGAT4B gene.[5][6]
This gene 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 A, 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. Therefore, the protein is essential for the production of tri- and tetra-antennary sugar chains. The encoded protein may play a role in regulating the availability of serum glycoproteins, oncogenesis, and differentiation.[6] Its affinities for donors of acceptors are lower than that of MGAT4A so it is suggested that it is not the main contributor in N-glycan biosynthesis.[7]