Ring-opening reactions of sucrose epoxides: Synthesis of 4′-derivatives of sucrose

The 2,1′-O-isopropylidene derivative (1) of 3-O-acetyl-4,6-O-isopropylidene-α-d-glucopyranosyl 6-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside and 2,3,4-tri-O-acetyl-6-O-trityl-α-d-glucopyranosyl 3,4-anhydro-1,6-di-O-trityl-β-d-lyxo-hexulofuranoside have been synthesised and 1 has been converted into 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-lyxo-hexulofuranoside (2). The S_N2 reactions of 2 with azide and chloride nucleophiles gave the corresponding 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-azido-4-deoxy-β-d-fructofuranoside (6) and 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-chloro-4-deoxy-β-d-fructofuranoside (8), respectively. The azide 6 was catalytically hydrogenated and the resulting amine was isolated as 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 4-acetamido-1,3,6-tri-O-acetyl-4-deoxy-β-d-fructofuranoside. Treatment of 5 with hydrogen bromide in glacial acetic acid followed by conventional acetylation gave 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,3,6-tri-O-acetyl-4-bromo-4-deoxy-β-d-fructofuranoside. Similar S_N2 reactions with 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl 1,6-di-O-acetyl-3,4-anhydro-β-d-ribo-hexulofuranoside (12) resulted in a number of 4′-derivatives of α-d-glucopyranosyl β-d-sorbofuranoside. The regiospecific nucleophilic substitution at position 4′ in 2 and 12 has been explained on the basis of steric and polar factors.     

Bromine oxidation of 1,2-O-isopropylidene-α-d-Glucofuranose and sucrose

Sucrose and $\text{1,2-O-}\text{isopropylidene-α-}\text{d}\text{-glucofuranose}$ (1) were oxidised with bromine in aqueous solution at pH 7 and room temperature. The resulting keto derivatives were converted into their more-stable O-methyloximes, which were characterised by spectroscopic and chromatographic methods. Oxidation of 1 occurred at C-3 and C-5, with a preference for C-5. In the sucrose derivatives isolated after oxidation, those having a keto group in the glucopyranosyl moiety preponderated. The axial fructofuranosyl aglycon protects position 3 in the glucopyranosyl group and oxidation occurs only at C-2 and C-4. Small amounts of sucrose oxidised at C-3 in the fructofuranosyl moiety were also found.     

Cyanobacterial alkaline/neutral invertases. Origin of sucrose hydrolysis in the plant cytosol?

The aim of this work was to investigate the occurrence of invertase (Inv) in cyanobacteria. We describe the first isolation and characterization of prokaryotic alkaline/neutral Inv (A/N-Inv) genes. Two genes (invA and invB) were identified in Anabaena sp. PCC 7120, which share about 50-56% identity with plant A/N-Inv and encode proteins of about 53-55 kDa. The identification of these proteins was confirmed by biochemical and immunological studies with recombinant proteins and with the enzymes isolated from Anabaena cells. Expression analysis supported the important role of A/N-Inv in nitrogen-fixing growth conditions. Nevertheless, A/N-Inv activities were shown in all filamentous and unicellular cyanobacteria investigated, regardless of their capacity to fix dinitrogen. Searches in complete sequenced genomes showed that A/N-Inv homologues are restricted to cyanobacterial species and plants. In particular, filamentous nitrogen-fixing strains display two A/N-Inv genes and unicellular strains have only one. Phylogenetic analysis leads us to suggest that modern plant A/N-Inv might have originated from an orthologous ancestral gene after the endosymbiotic origin of chloroplasts.     

Can sucrose affect polymerase chain reaction product formation?

Sucrose or trehalose at 0.3 M stabilised double-stranded DNA in PCR. Furthermore, the DNA polymerase from Thermus aquaticus was stabilised towards thermo-denaturation at 98°C by sucrose or trehalose. The effect was limited to these sugars and was shown not to be general for carbohydrates.     

Does sucrose influence the properties of DMPC vesicles?

Small-angle neutron and X-ray scattering, dynamic light scattering, X-ray diffraction coupled with differential scanning calorimetry, and Raman spectroscopy were applied to investigate unilamellar (ULVs) and multilamellar (MLVs) dimyristoylphosphatidylcholine (DMPC) vesicles in aqueous sucrose solutions with sucrose concentrations from 0 to 60% w/w. In case of ULVs, the addition of sucrose decreases the polydispersity of vesicle population. A minimum value of polydispersity was found at 20% sucrose. For sucrose concentration from 0 to 35% oligolamellar vesicles in the ULV population have a minimum presence. Vesicles with 5-10% sucrose exhibit the best stability in time. For the case of MLVs, sucrose influences the temperature of the phase transitions, but the internal membrane structure remains unchanged.     

Production of d(−)-lactate from sucrose and molasses

Escherichia coli W3110 derivatives, strains SZ63 and SZ85, were previously engineered to produce optically pure D(-) and L(+)-lactate from hexose and pentose sugars. To expand the substrate range, a cluster of sucrose genes (cscR' cscA cscKB) was cloned and characterized from E. coli KO11. The resulting plasmid was functionally expressed in SZ63 but was unstable in SZ85. Over 500 mM D(-)-lactate was produced from sucrose and from molasses by SZ63(pLOI3501).     

Glucose and sucrose: hazardous fast-food for industrial yeast?

Yeast cells often encounter a mixture of different carbohydrates in industrial processes. However, glucose and sucrose are always consumed first. The presence of these sugars causes repression of gluconeogenesis, the glyoxylate cycle, respiration and the uptake of less-preferred carbohydrates. Glucose and sucrose also trigger unexpected, hormone-like effects, including the activation of cellular growth, the mobilization of storage compounds and the diminution of cellular stress resistance. In an industrial context, these effects lead to several yeast-related problems, such as slow or incomplete fermentation, 'off flavors' and poor maintenance of yeast vitality. Recent studies indicate that the use of mutants with altered responses to carbohydrates can significantly increase productivity. Alternatively, avoiding unnecessary exposure to glucose and sucrose could also improve the performance of industrial yeasts.     

How does sucrose stabilize the native state of globular proteins?

It is well known that sucrose stabilizes the native state of globular proteins against both chemical denaturants and temperature. A largely accepted explanation of sucrose-induced stabilization is not yet emerged. It is shown that the same theoretical approach able to rationalize the occurrence of cold denaturation, the contrasting role of GdmCl and Gdm₂SO₄, and the TMAO counteraction of urea denaturing activity [PCCP 12 (2010) 14245; PCCP 13 (2011) 12008; PCCP 13 (2011) 17689] works well also in the case of sucrose. The solvent-excluded volume effect plays the fundamental role because sucrose addition to water causes a marked increase in volume packing density due to the large size of sucrose molecules, that act as crowding agents.     

Why does a sucrose choice reduce the consumption of alcohol in C57BL/6J mice?

To determine why animals reject alcohol when offered palatable solutions of sucrose, male C57BL/6J mice were challenged first with 5% sucrose then with 10% sucrose, while given continuous free-access to alcohol and water. The 5% sucrose dramatically reduced the intake of alcohol and increased the intake of total fluid by an average of 7.3 ml/day. The suppression of alcohol intake could not be attributed to a volumetric ceiling since access to 10% sucrose produced a further large increase in total intake (8.8 ml/day). The results support the interpretation that animals consume alcohol for characteristics it shares with sucrose.     

α-Galactosidase/sucrose kinase (AgaSK), a novel bifunctional enzyme from the human microbiome coupling galactosidase and kinase activities

α-Galactosides are non-digestible carbohydrates widely distributed in plants. They are a potential source of energy in our daily food, and their assimilation by microbiota may play a role in obesity. In the intestinal tract, they are degraded by microbial glycosidases, which are often modular enzymes with catalytic domains linked to carbohydrate-binding modules. Here we introduce a bifunctional enzyme from the human intestinal bacterium Ruminococcus gnavus E1, α-galactosidase/sucrose kinase (AgaSK). Sequence analysis showed that AgaSK is composed of two domains: one closely related to α-galactosidases from glycoside hydrolase family GH36 and the other containing a nucleotide-binding motif. Its biochemical characterization showed that AgaSK is able to hydrolyze melibiose and raffinose to galactose and either glucose or sucrose, respectively, and to specifically phosphorylate sucrose on the C6 position of glucose in the presence of ATP. The production of sucrose-6-P directly from raffinose points toward a glycolytic pathway in bacteria, not described so far. The crystal structures of the galactosidase domain in the apo form and in complex with the product shed light onto the reaction and substrate recognition mechanisms and highlight an oligomeric state necessary for efficient substrate binding and suggesting a cross-talk between the galactose and kinase domains.     

Do phospholipids and sucrose determine membrane phase transitions in dehydrating pollen species?

Gel-to-liquid crystalline transition temperatures (T_m) of phospholipids of five desiccation tolerant pollen species in vivo were compared at various levels of dehydration. In an attempt to explain chemically the differences in Tm between these species, phospholipids and soluble carbohydrate contents were examined. We observed a negative correlation between the number of double bonds per phospholipid and T_m values for the intact pollen. This negative correlation also applied to T_m and the relative amount of linolenic acid. For the purpose of comparing Tm values of pollen and of unsaturated PCs (from the literature), the relative amounts and degree of unsaturation of pollen PCs were determined. A discrepancy between Tm values of individual PCs and intact pollen is discussed. Sucrose is the major soluble carbohydrate in 15 pollen species tested, generally making up a considerable part of the dry weight. A positive correlation between sucrose content (either as a percentage of the dry weight or as grams sucrose per grams phospholipid) and T_m was established. This unexpected result was explained in terms of alternative adaptive strategies. We suggest that, for desiccation tolerance, pollen either has to contain sucrose for the protection of its phospholipids, or have a high degree of fatty acid unsaturation in its phospholipids. The advantages and disadvantages of the two options are discussed.     

Alginate–pectin co-encapsulation of dextransucrase and dextranase for oligosaccharide production from sucrose feedstocks

Bioprocess and Biosystems Engineering - The genes for dextransucrase and dextranase were cloned from the genomic regions of Leuconostoc mesenteroides MTCC 10508 and Streptococcus mutans MTCC 497,...     

Tomensides A–D,new antiproliferative phenylpropanoid sucrose esters from Prunus tomentosa leaves

To search for novel cytotoxic constituents against cancer cells as lead structures for drug development, four new 3-phenylpropanoid-triacetyl sucrose esters, named tomensides A–D (1–4), and three known analogs (5–7) were isolated from the leaves of Prunus tomentosa. Their structures were elucidated by spectroscopic analyses (1D, 2D NMR, CD and HRESIMS). The cytotoxic activities of all isolates against four human cancer cell lines (MCF-7, A549, HeLa and HT-29) were assayed, and the results showed that these isolates displayed stronger inhibitory activities compared with positive control 5-fluorouracil. Tomenside A (1) was the most active compound with IC₅₀ values of 0.11–0.62 μM against the four tested cell lines. The structure–activity relationship (SAR) of the isolates was also discussed. The primary screening results indicated that these 3-phenylpropanoid-triacetyl sucrose esters might be valuable source for new potent anticancer drug candidates.     

Origin of sucrose metabolism in higher plants: when,how and why?

Since the discovery of sucrose biosynthesis, considerable advances have been made in understanding its regulation and crucial role in the functional biology of plants. However, important aspects of this metabolism are still an enigma. Studies in cyanobacteria and the publication of the sequences of several complete genomes have recently significantly increased our knowledge of the structures of proteins involved in sucrose metabolism and given us new insights into their origin and further evolution.     

Enzymatic synthesis of l-DOPA α-glycosides by reaction with sucrose catalyzed by four different glucansucrases from four strains of Leuconostoc mesenteroides

l-DOPA α-glycosides were synthesized by reaction of l-DOPA with sucrose, catalyzed by four different glucansucrases from Leuconostoc mesenteroides B-512FMC, B-742CB, B-1299A, and B-1355C. The glucansucrases catalyzed the transfer of d-glucose from sucrose to the phenolic hydroxyl position-3 and -4 of l-DOPA. The glycosides were fractionated and purified by Bio-Gel P-2 column chromatography, and the structures were determined by ¹H NMR spectroscopy. The major glycoside was 4-O-α-d-glucopyranosyl l-DOPA, and the minor glycoside was 3-O-α-d-glucopyranosyl l-DOPA. The two glycosides were formed by all four of the glucansucrases. The ratio of the 4-O-α-glycoside to the 3-O-α-glycoside produced by the B-512FMC dextransucrase was higher than that for the other three glucansucrases. The glycosylation of l-DOPA significantly reduced the oxidation of the phenolic hydroxyl groups, which prevents their methylation, potentially increasing the use of l-DOPA in the treatment of Parkinson’s disease. The use of one enzyme, glucansucrase, and sucrose as the d-glucosyl donor makes the synthesis considerably simpler and cheaper than the formerly published procedure using cyclomaltodextrin and cyclomaltodextrin glucanyltransferase, followed by glucoamylase, and β-amylase hydrolysis.     

Substituting dietary linoleic acid with α-linolenic acid improves insulin sensitivity in sucrose fed rats

This study describes the effect of substituting dietary linoleic acid (18:2 n-6) with α-linolenic acid (18:3 n-3) on sucrose-induced insulin resistance (IR). Wistar NIN male weanling rats were fed casein based diet containing 22 energy percent (en%) fat with ～6, 9 and 7 en% saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) respectively for 3 months. IR was induced by replacing starch (ST) with sucrose (SU). Blends of groundnut, palmolein, and linseed oil in different proportions furnished the following levels of 18:3 n-3 (g/100 g diet) and 18:2 n-6/18:3 n-3 ratios respectively: ST-220 (0.014, 220), SU-220 (0.014, 220), SU-50 (0.06, 50), SU-10 (0.27, 10) and SU-2 (1.1, 2). The results showed IR in the sucrose fed group (SU-220) as evidenced by increase in fasting plasma insulin and area under the curve (AUC) of insulin in response to oral glucose load. In SU-220, the increase in adipocyte plasma membrane cholesterol/phospholipid ratio was associated with a decrease in fluidity, insulin stimulated glucose transport, antilipolytic effect of insulin and increase in basal and norepinephrine stimulated lipolysis in adipocytes. In SU-50, sucrose induced alterations in adipocyte lipolysis and antilipolysis were normalized. However, in SU-2, partial corrections in plasma insulin, AUC of insulin and adipocyte insulin stimulated glucose transport were observed. Further, plasma triglycerides and cholesterol decreased in SU-2. In diaphragm phospholipids, the observed dose dependent increase in long chain (LC) n-3 PUFA was associated with a decrease in LC-n-6 PUFA but insulin stimulated glucose transport increased only in SU-2. Thus, this study shows that the substitution of one-third of dietary 18:2 n-6 with 18:3 n-3 (SU-2) results in lowered blood lipid levels and increases peripheral insulin sensitivity, possibly due to the resulting high LCn-3 PUFA levels in target tissues of insulin action. These findings suggest a role for 18:3 n-3 in the prevention of insulin resistant states. The current recommendation to increase 18:3 n-3 intake for reducing cardiovascular risk may also be beneficial for preventing IR in humans.