B4GALT4 (beta-1,4-galactosyltransferase 4) is a Golgi-localized glycosyltransferase that catalyzes the transfer of galactose residues via beta-1,4 linkages to terminal N-acetylglucosamine moieties on glycoproteins and glycosphingolipids 123. Its primary function involves synthesizing N-acetyllactosamine units and participating in keratan sulfate proteoglycan biosynthesis through cooperation with sulfotransferases and glucosamine transferases 2. B4GALT4 also contributes to generating 6-sulfo-sialyl-Lewis X epitopes on mucin-type glycoproteins, which serve as ligands for L-selectin and regulate leukocyte migration 1. Enzymatic activity and proper Golgi localization require N-glycosylation at two sites, with mutations at Asn220 primarily affecting catalytic activity 4. Beyond glycan synthesis, B4GALT4 plays unexpected roles in cancer progression: it promotes hepatocellular carcinoma through microtubule spindle assembly regulation via the TGF-beta pathway 5, and it is implicated in osteoporosis development as part of an energy metabolism-related gene signature 6. Genome-wide association studies identified B4GALT4 as a suggestive locus associated with growth hormone responsiveness 7, indicating broader metabolic significance.