B3GALTL is the O-fucosyltransferase that transfers glucose toward fucose with a beta-1, 3 linkage.
B3GALTL specifically glucosylates O-linked fucosylglycan on TSP type-1 domains of proteins, thereby contributing to elongation of O-fucosylglycan.B3GALTL is a beta-1, 3-glucosyltransferase involved in the synthesis of the unusual O-linked disaccharide glucosyl-beta-1, 3-fucose-O- found on the thrombospondin (see THBS1; MIM 188060) type-1 repeats (TSRs) of many biologically important proteins.
Biosynthesis of glucosyl-beta-1, 3-fucose-O- is initiated by protein O-fucosyltransferase-2 (POFUT2; MIM 610249), which attaches the fucosyl residue to a serine or threonine within the TSR.
B3GALTL subsequently transfers the glucose onto TSR-fucose (Hess et al., 2008 [PubMed 18199743]).[supplied by OMIM].