Carbohydrate-based scaffolds in drug discovery

Carbohydrates have been proven as valuable scaffolds to display pharmocophores and the resulting molecules have demonstrated useful biological activity towards various targets including the somatostatin receptors (SSTR), integrins, HIV-1 protease, matrix metalloproteinases (MMP), multidrug resistance-associated protein (MRP), and as RNA binders. Carbohydrate-based compounds have also shown antibacterial and herbicidal activity.

Decreased hephaestin activity in the intestine of copper-deficient mice causes systemic iron deficiency

Copper and iron metabolism intersect in mammals. Copper deficiency simultaneously leads to decreased iron levels in some tissues and iron deficiency anemia, whereas it results in iron overload in other tissues such as the intestine and liver. The copper requirement of the multicopper ferroxidases hephaestin and ceruloplasmin likely explains this link between copper and iron homeostasis in mammals. We investigated the effect of in vivo and in vitro copper deficiency on hephaestin (Heph) expression and activity. C57BL/6J mice were separated into 2 groups on the day of parturition. One group was fed a copper-deficient diet and another was fed a control diet for 6 wk. Copper-deficient mice had significantly lower hephaestin and ceruloplasmin (~50% of controls) ferroxidase activity. Liver hepcidin expression was significantly downregulated by copper deficiency (~60% of controls), and enterocyte mRNA and protein levels of ferroportin1 were increased to 2.5 and 10 times, respectively, relative to controls, by copper deficiency, indicating a systemic iron deficiency in the copper-deficient mice. Interestingly, hephaestin protein levels were significantly decreased to ~40% of control, suggesting that decreased enterocyte copper content leads to decreased hephaestin synthesis and/or stability. We also examined the effect of copper deficiency on hephaestin in vitro in the HT29 cell line and found dramatically decreased hephaestin synthesis and activity. Both in vivo and in vitro studies indicate that copper is required for the proper processing and/or stability of hephaestin.

Genetic manipulation of blood group carbohydrates alters development and pathfinding of primary sensory axons of the olfactory systems

Primary sensory neurons in the vertebrate olfactory systems are characterised by the differential expression of distinct cell surface carbohydrates. We show here that the histo-blood group H carbohydrate is expressed by primary sensory neurons in both the main and accessory olfactory systems while the blood group A carbohydrate is expressed by a subset of vomeronasal neurons in the developing accessory olfactory system. We have used both loss-of-function and gain-of-function approaches to manipulate expression of these carbohydrates in the olfactory system. In null mutant mice lacking the alpha(1,2)fucosyltransferase FUT1, the absence of blood group H carbohydrate resulted in the delayed maturation of the glomerular layer of the main olfactory bulb. In addition, ubiquitous expression of blood group A on olfactory axons in gain-of-function transgenic mice caused mis-routing of axons in the glomerular layer of the main olfactory bulb and led to exuberant growth of vomeronasal axons in the accessory olfactory bulb. These results provide in vivo evidence for a role of specific cell surface carbohydrates during development of the olfactory nerve pathways. (c) 2006 Elsevier Inc. All rights reserved.

Screening, characterization and flocculating property of carbohydrate polymer from newly isolated Enterobacter cloacae WD7

A total of 188 carbohydrate polymer-producing bacterial strains were isolated from recycled sludge of five seafood processing plants. Among three selected isolates, identified as Enterobacter cloacae WD7, Enterobacter agglomerans WD50 and Pseudomonas alcaligenes WD22. E. cloacae WD7 generated a viscous culture broth exhibiting the highest flocculating activity and a crude polymer yield of 2.27 g/L after 3 days cultivation. Partial purification of this polymer was performed by precipitation with 95% ethanol, dialysis and freeze-drying. It was characterized as an acidic heteropolysaccharide, composed of neutral sugars (29.4%), uronic acids (14.2%) and amino sugars (0.93%). The functional group analysis by FT-IR spectroscopy showed the presence of hydroxyl, carboxyl, carbonyl and methoxyl groups. Thermal analysis by DSC showed the crystalline transition and the crystalline melting point (T-m) at 300 degrees C. This polysaccharide was soluble in water and insoluble in any organic solvents tested; gelation occurred under alkaline conditions in the presence of divalent cations in which copper as CuSO4 gave the best result. Studies on the flocculation property revealed that this polysaccharide was stable at 4-60 degrees C and pH 5-7. The optimal concentrations for the flocculating activity were 2 mg/L polysaccharide and 40 mM CaCl2 which played the synergistic effect on kaolin flocculation. Moreover, this polysaccharide could flocculate the kaolin suspension over a wide range of pH (pH 2-8) and temperature (4-50 degrees C) tested in the presence of CaCl2. (c) 2006 Elsevier Ltd. All rights reserved.

Dde as a protecting group for carbohydrate synthesis

Oligosaccharide synthesis using aminosugars requires the presence of a suitable amino protecting group. A number of protecting groups are currently used, and while many display favorable properties, most agents available still suffer from certain disadvantages. This report details the use of a hydrazine labile aminosugar protecting group, N -[1-(4,4-dimethyl-2,6-dioxocyclohex-1-ylidene)ethyl] (Dde), which can be introduced and removed in a facile and cost-effective manner.