A4GALT

Glycosyltransferase involved in biosynthesis of P1, P(k) and the rare NOR antigens of P1PK histo-blood group system. Catalyzes the transfer of galactose from UDP-alpha-D-galactose in an alpha1,4 linkage to lactosylceramide/beta-D-galactosyl-(1->4)-beta-D-glucosyl-(1<->1)-ceramide(d18:1(4E)) to produce globotriaosylceramide/globoside Gb3Cer (d18:1(4E)), also known as P(k) antigen or CD77. Globoside Gb3Cer/P(k)/CD77 is a root structure in biosynthesis pathway of neutral glycosphingolipids of the globo-series. Broadly expressed in cell membranes of immune cells and other tissues, Gb3Cer/P(k)/CD77 antigen may participate in mechanisms that regulate cell-cell interactions and cell differentiation. In germinal center B cells, Gb3Cer/CD77 interacts with CD19 to drive centroblast-to-centrocyte transition, B cell receptor complex assembly and T follicular helper cell differentiation. In epithelium, Gb3Cer regulates CDH1/E-cadherin-dependent cell-cell adhesion counteracting epithelial-to-mesenchymal transition (By similarity). Synthesizes P1 glycan epitope (alpha-D-Gal-(1->4)-beta-D-Gal-(1->4)-GlcNAc-R) by transferring a galactose moiety to paragloboside nLc4 or to complex-type N-glycans. Generates the rare NOR1 and NOR2 antigens which carry a Gal(alpha1->4)GalNAc terminal moiety and are both derived from Gb4Cer precursor. Also able to transfer galactose to galactosylceramide/beta-D-Gal-(1<->1')-Cer..

Function from UniProtKB (Q9NPC4), read 2026-09-23. CC BY 4.0.