β1,4-Galactosyltransferase (β4GalT)-IV Is Specific for GlcNAc 6-O-Sulfate

Abstract

The Gal␤134(SO 3 ؊ 36)GlcNAc moiety is present in various N-linked and O-linked glycans including keratan sulfate and 6-sulfosialyl-Lewis X, an L-selectin ligand. We previously found ␤1,4-galactosyltransferase (␤4GalT) activity in human colonic mucosa, which prefers GlcNAc 6-O-sulfate (6SGN) as an acceptor to nonsubstituted GlcNAc (Seko, A., Hara-Kuge, S., Nagata, K., Yonezawa, S., and Yamashita, K. (1998) FEBS Lett. 440, 307-310). To identify the gene for this enzyme, we purified the enzyme from porcine colonic mucosa. The purified enzyme had the characteristic requirement of basic lipids for catalytic activity. Analysis of the partial amino acid sequence of the enzyme revealed that the purified ␤4GalT has a similar sequence to human ␤4GalT-IV. To confirm this result, we prepared cDNA for each of the seven ␤4GalTs cloned to date and examined substrate specificities using the membrane fractions derived from ␤4GalT-transfected COS-7 cells. When using several Nlinked and O-linked glycans with or without 6SGN residues as acceptor substrates, only ␤4GalT-IV efficiently recognized 6SGN, keratan sulfate-related oligosaccharides, and Gal␤133(SO 3 ؊ 36GlcNAc␤136) GalNAc␣1-OpNP, a precursor for 6-sulfosialyl-Lewis X. These results suggested that ␤4GalT-IV is a 6SGN-specific ␤4GalT and may be involved in the biosynthesis of various glycoproteins carrying a 6-O-sulfated N-acetyllactosamine moiety.

Immunohistochemical expression of endometrial L-selectin ligand is higher in donor egg recipients with embryonic implantation

“…There are at least three molecules from a family of sialomucins (glycoproteins with multiple O-linked glycans) that are LSLs-endoglycan, podocalyxin, and CD34 -the latter two are found in humans (54). Furthermore, there are Ն10 enzymes implicated in key posttranslation modifications on the precursor proteins necessary for LSL functionality (63)(64)(65)(66)(67)(68)(69). Posttranslation modifications include galactosylation (69), fucosylation (67), sialylation (70), and sulfation (66).…”

“…Furthermore, there are Ն10 enzymes implicated in key posttranslation modifications on the precursor proteins necessary for LSL functionality (63)(64)(65)(66)(67)(68)(69). Posttranslation modifications include galactosylation (69), fucosylation (67), sialylation (70), and sulfation (66). There is tremendous overlap and redundancy in the production of this ligand, and therefore, a decrease in the level of a precursor molecule, or a decrease (but not elimination) in an enzyme responsible for posttranslation ligand modification, may not necessarily result in a decrease in functional LSL expression (54).…”

Phosphorylation and Sulfation of Oligosaccharide Substrates Critically Influence the Activity of Human β1,4-Galactosyltransferase 7 (GalT-I) and β1,3-Glucuronosyltransferase I (GlcAT-I) Involved in the Biosynthesis of the Glycosaminoglycan-Protein Linkage Region of Proteoglycans

“…On the other hand, Sato et al (40) show strong activity of the recombinant CSGalNAcT-2 toward sulfated oligosaccharide and polysaccharide CS substrates, suggesting that sulfation stimulates this CS-synthase and possibly elongation of CS chains. In a recent study, Seko et al (41) demonstrate that the ␤1,4-galactosyltransferase 4 preferred keratan sulfate-related oligosaccharides to nonsulfated GlcNAc residues as acceptor substrates. Altogether, these studies and our data support the idea that sulfation represents an important regulatory mechanism of GAG processing and assembly.…”

Polyoxometalates as effective inhibitors for sialyl- and sulfotransferases

“…Gal6ST, GlcNAc6ST-1, Gal 3-O-sulfotransferase-2 (Gal3ST-2), and b1,4-galactosyltransferase-I b4Gal-TI) were prepared as the membrane fractions from COS-7 cells as described previously [40][41][42]. b1,3-GlcNAc-transferase-2 (b3Gn-T2) was prepared from the culture medium of Pichia pastoris as described previously [21].…”