Disease relevance of B3GAT3

• These findings along with molecular modeling and three-dimensional structure comparison of the GlcAT-I catalytic center with that of the Bacillus subtilis glycosyltransferase SpsA provided evidence that the interactions of Asp195 with the ribose moiety of UDP and of Asp196 with the metal cation Mn2+ were crucial for GlcAT-I function [1].
• The GlcAT-I promoter was approx. 3-fold more active in a melanoma cell line than in a hepatoma cell line, providing evidence for the differential regulation of the gene's expression [2].

High impact information on B3GAT3

• We previously reported that IL-1beta down-regulated the expression and activity of GlcAT-I in primary rat chondrocytes [3].
• In concert, our investigations strongly indicated that GlcAT-I was able to control and reverse articular cartilage defects in terms of PG anabolism and GAG content associated with IL-1beta [3].
• Interestingly, GlcAT-I overexpression significantly enhanced GAG synthesis and deposition as evidenced by (35)S-sulfate incorporation, histology, estimation of GAG content, and fluorophore-assisted carbohydrate electrophoresis analysis [3].
• On the other hand, we showed that sulfation on C-6 position of Gal1 of the Galbeta1-3Gal analog markedly enhanced GlcAT-I catalytic efficiency and we demonstrated the importance of Trp243 and Lys317 residues of Gal1 binding site for enzyme activity [4].
• Phosphorylation and sulfation of oligosaccharide substrates critically influence the activity of human beta1,4-galactosyltransferase 7 (GalT-I) and beta1,3-glucuronosyltransferase I (GlcAT-I) involved in the biosynthesis of the glycosaminoglycan-protein linkage region of proteoglycans [4].

Biological context of B3GAT3

• Altogether, these results indicated that, similarly to the SpsA enzyme, the nucleotide binding site of GlcAT-I contains a XDD motif rather than a DXD motif [1].
• Thus, both GlcUAT-P and GlcUAT-I have overlapping substrate specificities [5].
• Transfection of a CHO cell mutant defective in GlcUAT-I with the hamster cDNA restored glycosaminoglycan assembly in vivo, confirming its identity [5].
• GlcAT-I expressed without the predicted N-terminal cytoplasmic tail or secreted as a polypeptide lacking the cytoplasmic tail and transmembrane domain was similarly organized as dimers, suggesting that the structural determinants for the dimerization state are localized in the luminal domain of the protein [6].
• Here we describe the characterization of the human glycosaminoglycan glucuronyltransferase I gene (GlcAT-I) and a related pseudogene [2].

Anatomical context of B3GAT3

• Nevertheless, the transfection of the GlcAT-I cDNA into COS-1 cells induced the significant expression of the HNK-1 epitope [7].
• Furthermore, we found that elevation of intracellular calcium concentration by the calcium ionophore ionomycin stimulated GlcAT-I gene expression as well as glycosaminoglycan chain synthesis in HeLa cells [8].

Associations of B3GAT3 with chemical compounds

• GlcAT-I transfers a glucuronic acid moiety from the uridine diphosphate-glucuronic acid (UDP-GlcUA) to the common linkage region trisaccharide Gal beta 1-3Gal beta 1-4Xyl covalently bound to a Ser residue at the glycosaminylglycan attachment site of proteoglycans [9].
• Furthermore, determination of the individual role of each aspartate showed that substitution of Asp195 as well as Asp196 to alanine strongly impaired GlcAT-I activity, whereas Asp194 replacement produced only a moderate alteration of the enzyme activity [1].
• We have investigated the role of aspartate residues Asp194-Asp195-Asp196 corresponding to the glycosyltransferase DXD signature motif, in GlcAT-I function by UDP binding experiments, kinetic analyses, and site-directed mutagenesis [1].
• In addition, the role of Cys(33) and Cys(301) in that process was investigated by site-directed mutagenesis combined with chemical modification of GlcAT-I by N-phenylmaleimide [6].
• Beta1,3-glucuronyltransferase (GlcAT-I) is an essential enzyme involved in heparan sulfate and chondroitin sulfate biosynthesis [10].

Regulatory relationships of B3GAT3

• However, the expression of the two genes was entirely different, with GlcUAT-I expressed in all tissues tested and GlcUAT-P expressed only in brain [5].

Other interactions of B3GAT3

• Our study demonstrates that GlcAT-I is organized as a homodimer as a result of disulfide bond formation mediated by Cys(33) localized in the stem region, whereas the residue Cys(301) localized in a conserved C-terminal domain is strictly required for the functional integrity of the enzyme [6].
• The present study identifies, for the first time, GlcAT-I as a target of calcium-dependent signaling pathway and evidences the critical role of Sp1 transcription factor in the activation of GlcAT-I expression [8].

Analytical, diagnostic and therapeutic context of B3GAT3

• Metabolic labeling and Western blot analyses further suggested that GlcAT-I expression led to an increase in the abundance rather than in the length of GAG chains [3].
• Northern blot analysis showed that GlcAT-I exhibited ubiquitous but markedly different expressions in the human tissues examined [2].
• The GlcAT-I gene was localized to human chromosome 11q12-q13 by in situ hybridization of metaphase chromosomes [2].
• To investigate the enzymatic properties of human GlcAT-I, we established an expression system for producing a soluble form of enzyme in the methylotrophic yeast Pichia pastoris and developed a three-step purification procedure using a combination of anion exchange, cation exchange and heparin chromatographies [11].

References