MGAT4B Gene: Function, Expression, and Disease Associations

MGAT4B encodes a Golgi enzyme, N-acetylglucosaminyltransferase IVb (GnT-IVb), which catalyzes the transfer of N-acetylglucosamine from UDP-GlcNAc to the core alpha-1,3-mannose of N-glycans, forming the GlcNAcβ1-4Manα1-3 branch. This modification is critical for the biosynthesis of complex-type N-glycans, influencing cell adhesion, receptor signaling, and glycoprotein stability. Mutations in MGAT4B are associated with congenital disorder of glycosylation type IIt (CDG IIt), and altered expression is observed in various cancers.

Tissue Expression

Cell Line Expression

Hotspot Mutations

Mutation functional classification

• REACT:21369 - N-glycan biosynthesis

• REACT:21618 - Biosynthesis of the N-glycan precursor (dolichol lipid-linked oligosaccharide)

• KEGG:00510 - N-Glycan biosynthesis

The MGAT4B protein (GnT-IVb) is a type II transmembrane glycosyltransferase localized to the Golgi apparatus. It consists of a short N-terminal cytoplasmic tail, a transmembrane domain, a stem region, and a large C-terminal catalytic domain facing the Golgi lumen. The enzyme adds a GlcNAc residue in β1-4 linkage to the α1-3 mannose of the N-glycan core, generating tri- and tetra-antennary structures. This activity is essential for the formation of complex N-glycans that modulate glycoprotein function, cell-cell interactions, and immune recognition.