B4GALT4
Description
The B4GALT4 (beta-1,4-galactosyltransferase 4) is a protein-coding gene located on chromosome 3.
Beta-1,4-galactosyltransferase 4 (B4GALT4) is an enzyme encoded by the B4GALT4 gene in humans. It belongs to a family of seven beta-1,4-galactosyltransferase (beta4GalT) genes, all of which encode type II membrane-bound glycoproteins. These proteins share a common function of transferring galactose in a beta1,4 linkage to specific acceptor sugars, including GlcNAc, Glc, and Xyl. Each beta4GalT enzyme exhibits distinct roles in the biosynthesis of various glycoconjugates and saccharide structures. As type II membrane proteins, they possess an N-terminal hydrophobic signal sequence that directs the protein to the Golgi apparatus and acts as a transmembrane anchor. Based on sequence similarity, the beta4GalTs are classified into four groups: beta4GalT1 and beta4GalT2, beta4GalT3 and beta4GalT4, beta4GalT5 and beta4GalT6, and beta4GalT7. B4GALT4, specifically, appears to primarily play a role in glycolipid biosynthesis. Two alternatively spliced transcript variants have been identified for this gene.
B4GALT4, also known as Beta-1,4-GalTase 4, Beta4Gal-T4, b4Gal-T4, is a galactosyltransferase that plays a crucial role in the synthesis of various glycoconjugates, including glycoproteins and glycosphingolipids. It specifically catalyzes the transfer of galactose (Gal) from UDP-Gal to the terminal N-acetyl glucosamine 6-O-sulfate (6-O-sulfoGlcNAc) within the linearly growing chains of keratan sulfate proteoglycans, both N- and O-linked. This process involves collaboration with other enzymes like B3GNT7, CHST6, and CHST1, leading to the construction and elongation of mono- and disulfated disaccharide units within the keratan sulfate polymer. Furthermore, B4GALT4 facilitates the transfer of Gal to the terminal 6-O-sulfoGlcNAc within the LacNac unit of core 2 O-glycans, resulting in the formation of 6-sulfo-sialyl-Lewis X (sLex). This sLex epitope, located on mucin-type glycoproteins, acts as a ligand for SELL/L-selectin, a key regulator of leukocyte migration. In the biosynthesis pathway of neolacto-series glycosphingolipids, B4GALT4 transfers Gal to the terminal GlcNAc of a lactotriaosylceramide (Lc3Cer) acceptor, forming a neolactotetraosylceramide. The interaction of B4GALT4 with SLC35A2 (isoform 2; UGT1) further highlights its complex roles in glycoconjugate biosynthesis.
B4GALT4 is also known as B4Gal-T4, beta4Gal-T4.
