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Physiological characteristics of human malignancies are increased glycolysis and overexpression of glucose transporters (GLUTs). 18Flurodeoxyglucose-positron emission tomography (FDG-PET) has successfully developed as clinical modality for the diagnosis and staging of many cancers based on the Warburg effect. To leverage this glucose transporter mediated metabolic disparity between normal and malignant cells, in the current report, protected, and de-protected glucose, mannose, galactose, rhamnose, maltose, and lactose-conjugated platinum(IV) complexes were designed and synthesized. The suggested potential of facilitated intravenous to oral switching of glycosylated platinum(IV) prodrugs with cancer-targeting properties were evaluated for glucose transporter 1 (GLUT1) and organic cation transporter 2 (OCT2)-mediated selective properties in vitro and in vivo. The cytotoxicity of 2d, 5d, and 6d were ~23-fold greater than that of the positive controls cisplatin, oxaliplatin, and satraplatin, respectively. The leading compound 6d, the IC50 of which with the GLUT1 inhibitor 4,6-oethylidene-α-D-glucose (EDG) and phloretin (31.80 and 38.71 μM) are 36- and 44-folds higher, respectively, than the 48 h IC50 (0.89 μM), is superior to the reported 5-8, exhibiting enhanced cancer targeting. The compounds also showed reduced toxicity to normal cells (293T IC50 = 12.06 μM and 3T3 cells IC50 > 100 μM) and exhibited no cross-resistance to cisplatin. Moreover, the encouraging selectivity of 6d for MCF-7 cells in vivo indicated that the pyranoside performs an important function in cancer targeting.

A novel synthesis of nucleotide sugars was conducted to prepare UDP-α-D-xylose and UDP-β-L-arabinose without utilizing protection strategies or advanced purification techniques. Sugar-1-phosphates of D-xylose and L-arabinose were synthesized from their β-glycosylsulfonylhydrazides and evaluated as substrates for recombinant UDP-sugar pyrophosphorylases from Arabidopsis thaliana or Bifidobacterium infantis to furnish the biologically active nucleotide. The facile, three-step procedure takes advantage of substrate diversity available through chemical synthesis followed by the selectivity of enzyme catalysis. This approach increases the substrate scope of enzymatic preparation and expands access to stereopure nucleotide sugars on preparative scale. Increased production of both sugars has implications for glycoengineering and glycan production using glycosyltransferases.

O-Linked β-N-acetylglucosaminyl transferase (OGT) plays an important role in the glycosylation of proteins, which is involved in various cellular events. In human, three isoforms of OGT (short OGT [sOGT]; mitochondrial OGT [mOGT]; and nucleocytoplasmic OGT [ncOGT]) share the same catalytic domain, implying that they might adopt a similar catalytic mechanism, including sugar donor recognition. In this work, the sugar-nucleotide tolerance of sOGT was investigated. Among a series of uridine 5'-diphosphate-N-acetylglucosamine (UDP-GlcNAc) analogs tested using the casein kinase II (CKII) peptide as the sugar acceptor, four compounds could be used by sOGT, including UDP-6-deoxy-GlcNAc, UDP-GlcNPr, UDP-6-deoxy-GalNAc and UDP-4-deoxy-GlcNAc. Determined values of Km showed that the substitution of the N-acyl group, deoxy modification of C6/C4-OH or epimerization of C4-OH of the GlcNAc in UDP-GlcNAc decreased its affinity to sOGT. A molecular docking study combined with site-directed mutagenesis indicated that the backbone carbonyl oxygen of Leu653 and the hydroxyl group of Thr560 in sOGT contributed to the recognition of the sugar moiety via hydrogen bonds. The close vicinity between Met501 and the N-acyl group of GlcNPr, as well as the hydrophobic environment near Met501, were responsible for the selective binding of UDP-GlcNPr. These findings illustrate the interaction of OGT and sugar nucleotide donor, providing insights into the OGT catalytic mechanism.

A detailed study was conducted to express and purify the putative [alpha]1,2-fucosyltransferase gene wbwK which is involved in O-antigen synthesis of Escherichia coli 086:B7. WbwK is found to display strict substrate specificity and only recognize Ga1[beta]1,3GalNAc[alpha]-OR (T-antigen and derivatives) and hence wbwK might have biomedical potential in masking the tumor antigen, T-antigen.

The O-antigen biosynthesis in Escherichia coli O86, an important bacterial strain that possesses strong blood group B activity is elucidated. A new bacterial glycosyltransferase equivalent to human blood group transferase B (GTB) is identified.

Modification of cell surface oligosaccharides by reactive oxygen species (ROS) and the biological effect of such modifications on cell adhesion were investigated. Treatment of HL60, a human promyelocyte leukemia cell line, with ROS, generated by a combination of hypoxanthine and xanthine oxidase (HX/XO), decreased the sialic acid content on the cell surface, as indicated by a flow cytometric analysis involving sialic acid-specific lectins, and a concomitant increase of free sialic acid was observed in the supernatant. A cell adhesion assay showed that the HX/XO treatment of HL60 cells decreases their capability of binding to human umbilical vein endothelial cells (HUVEC), probably because of an impairment of the interaction involving E-selectin, whereas the decrease in the binding was canceled by the addition of superoxide dismutase (SOD) and catalase. In fact, cell surface sialyl lewis x (sLex), but not lewis x (Lex), was decreased by HX/XO treatment. Thus, it is more likely that the impaired interaction is based on diminished levels of the selectin ligand. Cleavage of sialic acid by ROS was further verified by the degradation of 4MU-Neu5Ac by HX/XO in the presence of hydrogen peroxide and iron ion. These results indicate that glycosidic linkage of sialic acid is a potential target for superoxide and other related ROS. It is well known that ROS cause cellular damages such as lipid peroxidation and protein oxidation, but, as suggested by the findings reported in the literature, ROS may also regulate cell adhesion via the structural alteration of sialylated oligosaccharides on the cell surface. [ABSTRACT FROM AUTHOR]

Isoglobotriaosylceramide (iGb3) is a stimulatory antigen for a unique type of T cell, Natural Killer T cells. Produced in the lysosomal compartment by mammalian antigen-presenting cells, iGb3 is one of the few clearly identified carbohydrate ligands for biological receptors. A major source of glycoconjugate structural diversity arises from the possibility of forming different linkages between the same monosaccharide units. Globotriaosylceramide (Gb3) exists as a natural isomer for iGb3, and both isomers are frequently found together in mixtures of glycosphingolipids extracted from mammalian cell membranes. Discriminating these isomers has been feasible using monoclonal antibodies raised against specific carbohydrate epitopes, or by unambiguous structural characterization, which requires relatively large amounts of pure compounds isolated from grams, or tens of grams, of biological samples. However, the precise detection of iGb3 from small amounts of biological samples, where it may be mixed with Gb3 present in much higher abundance, is a prerequisite for answering further important biological questions such as stimulation of NKT cells. Here we describe a specific and sensitive method based on ion trap mass spectrometry to discriminate iGb3 from Gb3. We also demonstrate its application to quantifying the amount of iGb3 in a prototype antigen-presenting cell, rat RBL-CD1d cells, using a chemically synthesized short N-acyl chain iGb3 as internal standard. This methodology may have wide implications for functional glycosphingolipidomics of immune cells and glycosphingolipid biomarker analysis. [ABSTRACT FROM AUTHOR]