B3GALT1 encodes beta-1,3-galactosyltransferase 1, a Golgi-localized enzyme that catalyzes the transfer of galactose from UDP-galactose to substrates bearing terminal beta-N-acetylglucosamine residues, functioning in the biosynthesis of glycolipid and glycoprotein carbohydrate moieties. The enzyme exhibits strict substrate specificity, remaining inactive toward alpha-N-acetylglucosamine or alpha-N-acetylgalactosamine residues. B3GALT1 is involved in synthesizing sialyl Lewis a selectin ligands; histone deacetylase inhibitors upregulate B3GALT1 expression in normal prostatic cells to enhance sLe(a) production on MUC1 mucins 1, whereas cancer cells require both high B3GALT1 expression and MUC1 presence for sLe(a) synthesis 1. In extracellular vesicles, B3GALT1-modulated bisected GlcNAc glycosylation regulates the pre-metastatic immune microenvironment, promoting CD8+ T cell infiltration and reducing immune evasion in breast cancer metastasis 2. Clinically, B3GALT1 appears as a component of tumor mutation burden-related prognostic signatures in epithelial ovarian cancer and kidney renal papillary cell carcinoma, correlating with immune cell infiltration patterns and survival outcomes 34. However, a Parkinson's disease genome-wide association locus on chromosome 2.3 containing B3GALT1 appears to involve non-coding regulatory variants rather than B3GALT1 exonic changes 5.