The function of MGAT5B (alpha-1,6-mannosylglycoprotein 6-beta-N-acetylglucosaminyltransferase B, ENSG00000167889) is as follows. Glycosyltransferase that acts on alpha-linked mannose of N- glycans and O-mannosyl glycans. Catalyzes the transfer of N- acetylglucosamine (GlcNAc) to the beta 1-6 linkage of the mannose residue of GlcNAc-beta1,2-Man-alpha on both the alpha1,3- and alpha1,6- linked mannose arms in the core structure of N-glycan. Also acts on the GlcNAc-beta1,2-Man-alpha1-Ser/Thr moiety, forming a 2,6-branched structure in brain O-mannosyl glycan. Plays an active role in modulating integrin and laminin-dependent adhesion and migration of neuronal cells via its activity in the O-mannosyl glycan pathway. {ECO:0000269|PubMed:12941944, ECO:0000269|PubMed:14617637, ECO:0000269|PubMed:14623122, ECO:0000269|PubMed:16606368, ECO:0000269|PubMed:16857188, ECO:0000269|PubMed:19846580}.