Disease relevance of uridine diphosphate N-acetylglucosamine

• Here we present the 2.5-A crystal structure of Escherichia coli MurG in complex with its donor substrate, UDP-GlcNAc [1].
• We report the cloning and characterization of human UDP-GlcNAc 2-epimerase cDNA, with mutation analysis of three patients with sialuria [2].
• Previously, we reported that UDP-GlcNAc: Galbeta1-3GalNAcalphaRbeta1-6-N-acetylglucosaminyltransferas e (core 2 GlcNAc-T), a developmentally regulated enzyme of O-linked glycans biosynthesis pathway, is specifically increased in the heart of diabetic animals and is regulated by hyperglycemia and insulin [3].
• Membrane isolated from Bacillus subtilis strain 168 incorporated GlcNAc from UDP-GlcNAc directly onto undecaprenyl phosphate via transphosphorylation and subsequent transglucosylations [4].
• The UDP sugar-binding site of Gne was modeled by using the structure of the UDP-GlcNAc 4-epimerase WbpP from Pseudomonas aeruginosa [5].

High impact information on uridine diphosphate N-acetylglucosamine

• The sensitivity to other lectins of these cells and of CHO cells resistant to concanavalin A (ConA) has been determined, and their activity of UDP-N-acetyl-glucosamine glycoprotein N-acetyl-glucosaminyltransferase (GlcNAc-T) has been measured [6].
• Increased tissue concentrations of the end product of the hexosamine biosynthetic pathway, UDP-N-acetylglucosamine (UDP-GlcNAc), result in rapid and marked increases in leptin messenger RNA and protein levels (although these levels were much lower than those in fat) [7].
• UDP-GlcNAc 2-epimerase was found to be a major determinant of cell surface sialylation in human hematopoietic cell lines and a critical regulator of the function of specific cell surface adhesion molecules [8].
• To discern whether such an increase in the skeletal muscle UDP-GlcNAc concentration could account for the development of insulin resistance, we generated similar increases in muscle UDP-GlcNAc using three alternate experimental approaches [9].
• GlcN infusion raised plasma GlcN concentrations to approximately 1.2 mM and increased muscle and liver UDP-GlcNAc levels by 4-5-fold in all groups [10].

Chemical compound and disease context of uridine diphosphate N-acetylglucosamine

• The first enzyme of lipid A assembly in Escherichia coli is an acyltransferase that attaches an R-3-hydroxymyristoyl moiety to UDP-GlcNAc at the GlcNAc 3-OH [11].
• In biochemical studies, CMP-NeuAc (50 microM) inhibited the UDP-N-acetylglucosamine (UDP-GlcNAc) 2-epimerase of normal fibroblasts by 84-100%, but inhibited the epimerase from sialuria cells by only 19-31% [12].
• We now demonstrate that LpxA in cell extracts of Mesorhizobium loti and Leptospira interrogans, which synthesize lipid A molecules containing 2,3-diamino-2,3-dideoxy-d-glucopyranose (GlcN3N) units in place of glucosamine, do not acylate UDP-GlcNAc [13].
• The crystal structures of Streptococcus pneumoniae GlmU in unbound form, in complex with acetyl-coenzyme A (AcCoA) and in complex with both AcCoA and the end product UDP-GlcNAc, have been determined and refined to 2.3, 2.5, and 1.75 A, respectively [14].
• The O-antigen gene cluster of Escherichia coli O55:H7 and identification of a new UDP-GlcNAc C4 epimerase gene [15].

Biological context of uridine diphosphate N-acetylglucosamine

• This conclusion was an indirect one, based on the terminal glycosylation of this glycoprotein, a reaction that was dependent upon a Golgi-specific enzyme, UDP-GlcNAc transferase I. We show here that the Golgi fraction of rat liver will substitute for members of CHO cells as a source of transferase I in this reaction [16].
• The glmUS operon, encoding proteins necessary for the synthesis of GlcN (glmS) and the formation of UDP-GlcNAc (glmU), is transcribed from two promoters located upstream of glmU [17].
• Thus, EMeg32-dependent UDP-GlcNAc levels influence cell cycle progression and susceptibility to apoptotic stimuli [18].
• Here, we show that transgenic overexpression of an enzyme using UDP-GlcNAc to modify proteins with O-GlcNAc produces the type 2 diabetic phenotype [19].
• The above results demonstrate that the mammalian Golgi UDP-GlcNAc transporter gene has all of the necessary information for the protein to be expressed and targeted functionally to the Golgi apparatus of yeast and that two proteins with very different amino acid sequences may transport the same solute within the same Golgi membrane [20].

Anatomical context of uridine diphosphate N-acetylglucosamine

• These conditions all resulted in very similar increases in the skeletal muscle UDP-GlcNAc (to approximately 55 nmol/gram) and markedly impaired glucose uptake and glycogen synthesis [9].
• Mouse embryonic fibroblasts (MEFs) deficient for EMeg32 exhibit defects in proliferation and adhesiveness, which could be complemented by stable re-expression of EMeg32 or by nutritional restoration of intracellular UDP-GlcNAc levels [18].
• The cumulative data indicate that early GPI intermediates are primarily located in the cytoplasmic leaflet of the ER, and are probably synthesized from PI located in the cytoplasmic leaflet and UDP-GlcNAc synthesized in the cytosol [21].
• The need of UDP-GlcNAc 2-epimerase for a defined sialylation process is exemplified with the polysialylation of the neural cell adhesion molecule in embryonic stem cells [22].
• This lipid is also made when membranes are incubated with [1-14C]palmitoyl-CoA and UDP-GlcNAc [23].

Associations of uridine diphosphate N-acetylglucosamine with other chemical compounds

• We have determined the X-ray crystal structure of the catalytic fragment of GnT I in the absence and presence of bound UDP-GlcNAc/Mn(2+) at 1.5 and 1.8 A resolution, respectively [24].
• We have recently identified the murine glucosamine-6-phosphate (GlcN6P) acetyltransferase, EMeg32, as a developmentally regulated enzyme on the route to UDP-N:-acetylglucosamine (UDP-GlcNAc) [18].
• The sugar donors, GDP-mannose and UDP-GlcNAc, must first be transported from the cytosol, their site of synthesis, via specific Golgi membrane transporters into the lumen where they are substrates in the biosynthesis of these mannoproteins [25].
• GlcNAc-phosphotransferase transferred GlcNAc 1-phosphate from UDP-GlcNAc to the synthetic acceptor alpha-methylmannoside, generating GlcNAc-1-phospho-6-mannose alpha-methyl, the structure of which was confirmed by mass spectroscopy [26].
• Hen oviduct membrane preparations were labeled with combinations of UDP-GlcNAc, GDP-Man, and UDP-Glc [27].

Gene context of uridine diphosphate N-acetylglucosamine

• Microsomal membranes from cells repressed for ALG13 or ALG14, as well as detergent-solubilized extracts thereof, were unable to catalyze the transfer of N-acetylglucosamine from UDP-GlcNAc to [(14)C]GlcNAc(1)-PP-Dol, but did not impair the formation of GlcNAc(1)-PP-Dol or GlcNAc-GPI [28].
• Isolation of null alleles of the Caenorhabditis elegans gly-12, gly-13 and gly-14 genes, all of which encode UDP-GlcNAc: alpha-3-D-mannoside beta1,2-N-acetylglucosaminyltransferase I activity [29].
• Our results indicate that YEA4 encodes an ER-localized UDP-GlcNAc transporter that is required for cell wall chitin synthesis in S. cerevisiae [30].
• These results demonstrate that the UAP1 genes indeed specify eukaryotic UDP-GlcNAc pyrophosphorylase and that phosphomutase reaction precedes uridyltransfer [31].
• GFAT2 was modestly inhibited (15%) by UDP-GlcNAc but not through detectable O-glycosylation [32].

Analytical, diagnostic and therapeutic context of uridine diphosphate N-acetylglucosamine

• We report that inactivation of the UDP-GlcNAc 2-epimerase by gene targeting causes early embryonic lethality in mice, thereby emphasizing the fundamental role of this bifunctional enzyme and sialylation during development [22].
• Gel filtration analysis of purified UDP-GlcNAc 2-epimerase/ManNAc kinase showed that the polypeptide self-associates as a dimer and as a hexamer with apparent molecular masses of 150 and 450 kDa, respectively [33].
• The covalent structure of the monoacylated UDP-GlcNAc product was established by fast atom bombardment mass spectrometry and 1H-NMR spectroscopy [34].
• Circular dichroism (CD) was used to investigate the secondary structure of a recombinant, soluble form of the enzyme and its interaction with UDP-GlcNAc and an inhibitory substrate analog [35].
• Spectrophotometric assays, capillary electrophoresis, and mass spectrometry analyses showed that FlaA1 is a novel bifunctional C(6) dehydratase/C(4) reductase specific for UDP-GlcNAc [36].

References