Participates in O-mannosyl glycosylation by catalyzing the addition of N-acetylglucosamine to O-linked mannose on glycoproteins ( ). Catalyzes the synthesis of the GlcNAc(beta1-2)Man(alpha1-)O-Ser/Thr moiety on alpha-dystroglycan and other O-mannosylated proteins, providing the necessary basis for the addition of further carbohydrate moieties (, ). Is specific for alpha linked terminal mannose and does not have MGAT3, MGAT4, MGAT5, MGAT7 or MGAT8 activity.
Subcellular locations: Golgi apparatus membrane
Constitutively expressed. An additional weaker band is also detected in spinal cord, lymph node, and trachea. Expressed especially in astrocytes. Also expressed in immature and mature neurons.