Beta1,3-NAcetylgalactosaminyltransferase 1 (B3GALNT1)

Abstract

Globoside (globotetraosylceramide, Gb4, GalNAcβl-3Galαl-4Galβ1-4G1c-Cer), a globo-series glycosphingolipid member, is also known as the P antigen in the P histo-blood group system and synthesized by the addition of GalNAc in β-l,3-linkage to the terminal Gal residue of globotriaosylceramide (Gb3). This reaction is catalyzed by UDP-GalNAc: β-1,3-N-acetylgalactosaminyltransferase 1 (B3GALNT1). This enzyme is also called globoside synthase. This gene was first isolated as a β-1,3-galactosyltransferase by using sequence homology from human (Amado et al. 1998) and mouse (Hennet et al. 1998) and termed B3GALT3. Subsequently the genuine β-1,3-N-acetylgalactosaminyltransferase activity was identified by using expression cloning (Okajima et al. 2000), and thereby the gene was renamed as B3GALNT1. This gene was also isolated as a homologue of the Drosophila brainiac gene (Vollrath et al. 2001). Disruption of the B3galnt3 gene in mouse showed embryonic lethality (Vollrath et al. 2001), in which finding suggests that B3GALNT1 has a dual function considering that the Gb3 synthase (A4GALT) knockout mouse that systemically lacks all the globo-series glycosphingolipids is normally born (Okuda et al. 2006).