B4GALNT2 transfers GalNAc from UDP-GalNAc to Sial-Gal-GlcNAc-Gal to form the Sd(a) antigen on UMOD

Stable Identifier
Reaction [transition]
Homo sapiens
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The histo-blood group antigen Sda was discovered to be a dominant character found in more than 90 % of Caucasian red blood cells. In addition to erythrocytes, the Sda antigen is also found in other tissues and body fluids, particularly in urine of humans and other mammals. The Sda antigen shares a common minimal saccharide structure (GalNAc-beta1-4[Neu5Ac-alpha2-3]Gal-beta-) with the Cad antigen. Both antigens contain a pentasaccharide structure, the Sda antigen's structure being GalNAc-beta1-4[Neu5Ac-alpha2-3]Gal-beta1-4GlcNAc-beta1-3Gal. The last step in the biosynthesis of both Sda and Cad antigens is catalysed by beta-1,4 N-acetylgalactosaminyltransferase 2 (B4GALNT2), a Golgi membrane protein that transfers N-acetylgalactosamine (GalNAc) from UDP-GalNAc to position C4 of the Gal residue of the Neu5Ac-alpha2-3Gal-beta1 sequence (Montiel et al. 2003, Lo Presti et al. 2003, Dall'Olio et al. 2014). Both antigens can be expressed by N- or O-linked chains of glycoproteins. Tamm–Horsfall glycoprotein (THGP, aka UMOD) is a major carrier of the Sda antigen in urine (Soh et al. 1980, Serafini-Cessi & Conte 1982). After proteolytic cleavage, UMOD is secreted into the urine where it may play roles in colloid osmotic pressure, retarding passage of positively charged electrolytes, preventing urinary tract infection and modulateing formation of supersaturated salts and their crystals (Schmid et al. 2010).

Literature References
PubMed ID Title Journal Year
20798515 Uromodulin facilitates neutrophil migration across renal epithelial monolayers

Pfaller, W, Bertocchi, C, Jennings, P, Joannidis, M, Prajczer, S, Gruber, LN, Schmid, M, Gandini, R

Cell. Physiol. Biochem. 2010
12678917 Molecular cloning, gene organization and expression of the human UDP-GalNAc:Neu5Acalpha2-3Galbeta-R beta1,4-N-acetylgalactosaminyltransferase responsible for the biosynthesis of the blood group Sda/Cad antigen: evidence for an unusual extended cytoplasmic domain

Delannoy, P, Krzewinski-Recchi, MA, Montiel, MD, Harduin-Lepers, A

Biochem. J. 2003
14688233 Molecular cloning of the human beta1,4 N-acetylgalactosaminyltransferase responsible for the biosynthesis of the Sd(a) histo-blood group antigen: the sequence predicts a very long cytoplasmic domain

Cabuy, E, Dall'Olio, F, Chiricolo, M, Lo Presti, L

J. Biochem. 2003
7072193 Precipitin reaction between Sda-active human Tamm-Horsfall glycoprotein and anti-Sda-serum

Conte, R, Serafini-Cessi, F

Vox Sang. 1982
6156677 The relationship between the N-acetylgalactosamine content and the blood group Sda activity of Tamm and Horsfall urinary glycoprotein

Morgan, WT, Watkins, WM, Donald, AS, Soh, CP

Biochem. Biophys. Res. Commun. 1980
24112972 The expanding roles of the Sd(a)/Cad carbohydrate antigen and its cognate glycosyltransferase B4GALNT2

Dall'Olio, F, Chiricolo, M, Malagolini, N, Trinchera, M, Harduin-Lepers, A

Biochim. Biophys. Acta 2014
Catalyst Activity

acetylgalactosaminyltransferase activity of B4GALNT2 [Golgi membrane]

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