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Rare sugars are known for their ability to suppress postprandial blood glucose levels. Therefore, oligosaccharides and disaccharides derived from rare sugars could potentially serve as functional sweeteners. A disaccharide [α-d-allopyranosyl-(1→2)-β-d-psicofuranoside] mimicking sucrose was synthesized from rare monosaccharides D-allose and D-psicose. Glycosylation using the intermolecular aglycon delivery (IAD) method was employed to selectively form 1,2-cis α-glycosidic linkages of the allopyranose residues. Moreover, β-selective psicofuranosylation was performed using a psicofuranosyl acceptor with 1,3,4,6-tetra-O-benzoyl groups. This is the first report on the synthesis of non-reducing disaccharides comprising only rare d-sugars by IAD using protected ketose as a unique acceptor; additionally, this approach is expected to be applicable to the synthesis of functional sweeteners. [ABSTRACT FROM AUTHOR]

A rare sugar, allose, was reported to inhibit the development of Plasmodium parasites in Anopheles mosquitoes; however, the mechanism remains unknown. The present study addressed the inhibitory mechanism of allose on the development of the Plasmodium parasite by connecting it with bacteria involvement in the midgut. In addition, further inhibitory sugars against Plasmodium infection in mosquitoes were explored. Antibiotic-treated and antibiotic-untreated Anopheles stephensi were fed fructose with or without allose. The mosquitoes were infected with luciferase-expressing Plasmodium berghei, and parasite development was evaluated by luciferase activity. Bacterial composition analysis in gut of their mosquitoes was performed with comprehensive 16S ribosomal RNA sequencing. As the result, allose inhibited the development of oocysts in mosquitoes regardless of prior antibiotic treatment. Microbiome analysis showed that the midgut bacterial composition in mosquitoes before and after blood feeding was not affected by allose. Although allose inhibited transient growth of the midgut microbiota of mosquitoes after blood feeding, neither toxic nor inhibitory effects of allose on the dominant midgut bacteria were observed. Ookinete development in the mosquito midgut was also not affected by allose feeding. Additional 15 sugars including six monosaccharides, four polyols, and five polysaccharides were tested; however, no inhibitory effect against Plasmodium development in mosquitoes was observed. These results indicated that allose inhibits parasite development in midgut stage of the mosquito independently of midgut microbiota. Although further studies are needed, our results suggest that allose may be a useful material for the vector control of malaria as a “transmissionblocking sugar.” [ABSTRACT FROM AUTHOR]

Testing of foods for low levels of the human pathogen, Listeria monocytogenes (Lm), involves a selective enrichment procedure. A nonpathogenic species of Listeria, L. innocua (Li), is often present in foods and food-manufacturing environments and is an interference organism for Lm detection due to competition during enrichment. The present study investigated whether a novel enrichment strategy incorporating the sugar allose into the secondary enrichment broth (allose method) could improve the detection of Lm from foods when Li is present. First, Canadian food isolates of Listeria spp. were tested to confirm recent reports that lineage II Lm (LII-Lm), but not Li, could metabolize allose. All LII-Lm isolates (n = 81), but not Li (n = 36), possessed the allose genes lmo0734-lmo0739, and could efficiently metabolize allose. Next, smoked salmon was contaminated with mixtures of LII-Lm and Li and tested using different enrichment procedures to compare the ability to recover Lm. Allose broth was more effective than Fraser Broth, with Lm detected in 87% (74 of 85) compared to 59% (50 of 85) of the samples (P

Epimerization of abundant monosaccharides derived from lignocellulosic biomass offers an attractive approach for the synthesis of rare sugars. Molybdenum-based catalysts demonstrate excellent glucose-mannose epimerization performance, but most studies have neglected the synthesis of other sugar epimers and the pathways of their formation. Here, reduced Beta zeolite supported MoO x catalysts (Mo/Beta) with 1.5–10 wt% Mo loading were examined for glucose epimerization in water, specifically focusing on the formation of the rare sugars allose and altrose. The physicochemical structure and the catalytic activity of the catalyst were examined in detail, and the reaction mechanisms for the epimer formation were probed by nuclear magnetic resonance (NMR) spectroscopy. The results demonstrate that 5 wt% Mo/Beta achieved a near-equilibrium mannose yield of 30 % from glucose within 10 min at reaction temperatures below 140 °C, exhibiting a relatively low activation energy (∼67 kJ mol−1). At elevated reaction temperatures (≥ 120 °C), the rare sugars allose and altrose accumulated to combined yields of 24 % at 140 °C. An isotope labelling study using NMR spectroscopy corroborated the catalysis to involve 1,2-carbon shifts that elicit the formation of rare sugars at sufficiently high temperatures. Evaluation of catalyst reuse and regeneration indicated that supported MoO x had higher stability than MoO 3 , but the stability of the Mo/Beta catalysts under hydrothermal conditions leaves room for improvement. [Display omitted] • Beta zeolite supported MoO x efficient catalyst for aqueous glucose epimerization. • 5 wt% Mo/Beta yields 30 % mannose from glucose at 120 °C with low E a of 67 kJ mol−1. • Formation of the rare sugars allose and altrose in 24 % yield from glucose at 140 °C. • NMR study with 13C-glucose shows 1,2-carbon shift elicits allose/altrose formation. [ABSTRACT FROM AUTHOR]

D-Allose, a C3 epimer of D-glucose, has potential to improve human health as a functional food. However, its effect on the intestinal environment remains unknown. Aged humans progressively express changes in the gut, some of which deleteriously affect gastrointestinal health. In this study, we profiled the intestinal microbiome in aged mice and analyzed organic acids produced by bacteria in cecum contents after long-term ingestion of D-allose. D-Allose did not significantly change organic acid concentration. However, long-term ingestion did significantly increase the relative abundance of Actinobacteria and reduce the relative abundance of Proteobacteria. These results suggest that oral D-allose improves the proportion of favorable intestinal flora in aged mice. D-Allose significantly decreased the relative abundance of Lachnospiraceae bacteria, but increased the relative abundance of Bacteroides acidifaciens and Akkermansia muciniphila. Thus, D-allose might serve as a nutraceutical capable of improving the balance of gut microbiome during aging. [ABSTRACT FROM AUTHOR]

• Raphia hookeri (RH) is an underutilized palm crop native to Africa. • Its ethnomedicinal, phytochemistry and biotechnological applications are appraised. • RH's metabolites could support its inherent industrial and therapeutic significance. • "-omics" could provide supportive data on its safety and health benefits. • The study provided baseline information that will inspire further investigations on RH. Raphia hookeri G. Mann & H. Wendl (Arecaceae), commonly known as 'Raffia Palm' is an underutilized plant native to Africa. Like other palms, it is a good source of medicine with diverse ethnomedicinal and industrial applications. Despite these discernible therapeutic and economic benefits of R. hookeri , the plant remains underutilized, albeit some achievement has been made in this area. Hence, this review highlights the existing scope and knowledge gaps regarding its folkloric uses and phytochemistry with a view to lending credence to its pharmacological properties, particularly in the treatment of diabetes. Information are also provided on its biotechnological applications. Despite the pharmacological significance and ethnomedicinal uses of R. hookeri , a major challenge that persists is the lack of comprehensive data on its phytochemical characterization as well as inadequate information on its pharmacokinetics and pharmacodynamics. In view of this, the concepts of molecular dynamics and "-omics" (genomics, proteomics, metabolomics, and transcriptomics etc.) as currently being embraced as modern strategies enhancing translational studies, could find relevance and may provide more comprehensive data supporting the safety profile and therapeutic efficacy of R. hookeri against markers implicated in the pathogenesis and physiological perturbations associated with diseases. These strategies are proposed for adoption in future studies seeking to provide evidence-based data on the therapeutic scope and overall economic benefits of R. hookeri. [ABSTRACT FROM AUTHOR]

Two rarely phenolic acid-substituted alloses (1, 2) and one new glucoside (3), as well as nine known compounds (4–12) were isolated from rhizomes of Cibotium barometz (L.) J. Sm. Structures of 1–3 were established by extensively spectroscopic analyses (NMR, MS, etc.) and acid hydrolysis. All compounds were evaluated for the hepatoprotective activities against APAP-induced HepG2 cell damage. Compounds 1, 4–7, 10 exhibited significant hepatoprotective activities, even more strongly than positive control, bicycol. In addition, compounds 1 and 9 could reduce PC12 cell death induced by serum deprivation. [ABSTRACT FROM AUTHOR]

d-Allose is a rare monosaccharide, which rarely appears in the natural environment. d-Allose has an 80% sweetness relative to table sugar but is ultra-low calorie and non-toxic and is thus an ideal candidate to take the place of table sugar in food products. It displays unique health benefits and physiological functions in various fields, including food systems, clinical treatment, and the health care fields. However, it is difficult to produce chemically. The biotechnological production of d-allose has become a research hotspot in recent years. Therefore, an overview of recent studies on the physiological functions, applications, and biotechnological production of d-allose is presented. In this review, the physiological functions of d-allose are introduced in detail. In addition, the different types of d-allose-producing enzymes are compared for their enzymatic properties and for the biotechnological production of d-allose. To date, very little information is available on the molecular modification and food-grade expression of d-allose-producing enzymes, representing a very large research space yet to be explored. [ABSTRACT FROM AUTHOR]

The present study was designed to evaluate the effect of one rare sugar, D‑allose, on normal human cells and cutaneous tissue, and to investigate the radiosensitizing and chemosensitizing potential of D‑allose in an in vivo model of head and neck cancer. Results indicated that D‑allose did not inhibit the growth of normal human fibroblasts TIG‑1 cells, and no apoptotic changes were observed after D‑allose and D‑glucose treatment. The mRNA expression levels of thioredoxin interacting protein (TXNIP) in TIG‑1 cells after D‑allose treatment increased by 2‑fold (50.4 to 106.5). Conversely, the mRNA expression levels of TXNIP in HSC3 cancer cells increased by 74‑fold (1.5 to 110.6), and the thioredoxin (TRX)/TXNIP ratio was markedly reduced from 61.7 to 1.4 following D‑allose treatment. Combined multiple treatments with docetaxel, radiation and D‑allose resulted in the greatest antitumor response in the in vivo model. Hyperkeratosis, epidermal thickening and tumor necrosis factor‑α immunostaining were observed following irradiation treatment, but these pathophysiological reactions were reduced following D‑allose administration. Thus, the present findings suggest that D‑allose may enhance the antitumor effects of chemoradiotherapy whilst sparing normal tissues. [ABSTRACT FROM AUTHOR]

Listeriosis, the disease caused by pathogenic Listeria species, can present severe symptoms in susceptible people. The goal of this study was to develop a novel enrichment broth, Listeria allose enrichment broth (LAEB), to improve isolation of Listeria monocytogenes and Listeria ivanovii from samples through incorporating a specific carbohydrate and reducing inhibitor concentrations. Other coexisting bacteria, particularly Listeria innocua, can interfere with the isolation of pathogenic Listeria in such ways as overgrowth of L. innocua and the generation of inhibitory metabolites. The incorporation of allose into the novel LAEB was effective for slowing the growth of L. innocua and other nontarget microorganisms. We determined that 35°C and pH 7.0 under aerobic conditions are optimal for Listeria growth in this medium. The novelty of the use of LAEB is the single enrichment procedure at 35°C for 24 h, obviating the need for a secondary enrichment medium. In 50 simulated samples, the sensitivity of the LAEB method (86%) was higher than that of the International Organization for Standardization (EN ISO) method (70%). In 142 naturally contaminated samples tested, the isolation rate for pathogenic Listeria with the LAEB method was 26.0% (37 of 142 samples), which was significantly higher than the 17.6% (25 of 142 samples) for the EN ISO method. Higher isolation rates and a quicker and easier protocol make the novel LAEB method an appropriate alternative for the isolation of pathogenic Listeria. [ABSTRACT FROM AUTHOR]

From the bark of Ladenbergia hexandra Klotzsch, ten triterpenoid glycosides were isolated along with five known compounds, and their structures were determined based on extensive NMR and mass spectroscopic, GC and HPLC analyses. Some triterpenoid glycosides contained 6-deoxy-D-allose or D-allose as a sugar moiety. The absolute stereochemical assignment of the sugars was determined by comparison with synthetic samples, as well as by GC and HPLC analysis. [ABSTRACT FROM AUTHOR]

Diacetone- d -allose is an important building block for the synthesis of pharmaceutical ingredients. The current batch production process involves a chemical oxidation and a reduction step that include hazardous reagents, produce a large amount of waste and require an extensive downstream processing. Current investigations aim to develop a catalytic reduction process of the intermediate diacetone- d -ketoglucose (DAKG) with molecular hydrogen, a green solvent, and a heterogeneous metal catalyst. Improvement of productivity and simultaneous reduction of the environmental impact shall be achieved by transforming the conventional batch procedure into a continuous process with a stationary catalyst packing. The screening studies presented in this work revealed that high reaction rates and a high selectivity (>98%) can be achieved with a commercial platinum catalyst under mild conditions in an aqueous buffer solution. Transition from batch into a continuous process was realized in several mini-scale fixed bed reactors to provide a fast screening and high mass transfer rates. A high selectivity (99%) and a conversion of 30% was achieved. The results indicate that the reactor performance was influenced by internal diffusion limitations and also by external mass transfer. To attain full conversion of DAKG, the reaction was performed in a random packed bed reactor and a selectivity of >96% was achieved. [ABSTRACT FROM AUTHOR]

Our early experiments confirmed that D-allose was closely involved in the blood brain barrier (BBB) protection from ischemia reperfusion (IR) injury, but the regulatory mechanism is not fully defined. In this study, we aimed to investigate the role of D-allose in the protection of BBB integrity and the relevant mechanisms involved in the mice model of middle cerebral artery occlusion and reperfusion (MCAO/Rep). D-allose was intravenously injected via a tail vein (0.2 mg/g and 0.4 mg/g, 1 h before ischemia), GW9662 was intraperitoneal injected to the mice (4 mg/kg) before inducing ischemia 24 h. Pretreatment with D-allose ameliorated the neurological deficits, infarct volume and brain edema in brains of MCAO/Rep mice. D-allose inhibited cell apoptosis in the mice model of MCAO/Rep. We observed that D-allose remarkably decreased BBB permeability and prevented the reduction of ZO-1, Occludin and Claudin-5 in mice brains with MCAO/Rep injury. D-allose also repressed the levels of TNF-α, NF-κB, interleukin (IL)-1β and IL-8 in inflammatory responses. The increases of intercellular adhesion molecular-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and CD11b/CD18 were significantly inhibited by D-allose during the MCAO/Rep injury. And D-allose decreased the L-selectin and P-selectin levels after MCAO/Rep. Moreover, D-allose induced up-regulation of peroxisome proliferator-activated receptor γ (PPARγ), and down-regulation of TNF-α and NF-κB after MCAO/Rep, which were abolished by utilization of GW9662. In conclusion, we provided evidences that D-allose may has therapeutic potential against brain IR injury through attenuating BBB disruption and the inflammatory response via PPARγ-dependent regulation of NF-κB. [ABSTRACT FROM AUTHOR]

[Figure not available: see fulltext.] Ketone derived from diacetone-α-D-glucose is a suitable starting material for the synthesis of 3- C-linked glycohybrids containing 1,2,3-triazole moiety as an intersugar linkage. The pyranose tautomers of 3-deoxy-3-(1,2,3-1 H-triazol-1-yl)glucose, 3- C-[(1,2,3-1 Htriazol-1-yl)methyl]allose and 3- C-[(1,2,3-1 H-triazol-1-yl)methyl]gulose moieties are released upon the acidic hydrolysis of the corresponding O-isopropylidene-protected furanosyl-type synthetic intermediates. Some of the title compounds show a rare property of activating β-galactosidase from Escherichia coli. [ABSTRACT FROM AUTHOR]

Purpose: The anti-tumor activity of glucose analogs 2-deoxy-glucose (2-DG) and D-allose was investigated alone or in combination with p38 mitogen-activated protein kinase (MAPK) inhibitor SB202190 or platinum analogs as a strategy to pharmacologically target glycolytic tumor phenotypes. Methods: Hypoxia inducible factor-1 alpha (HIF-1α) protein accumulation in pancreatic cell lines treated with SB202190 alone and in combination with glucose analogs was analyzed by Western blot. HIF-1α transcriptional activity was measured in MIA PaCa-2 cells stably transfected with a hypoxia response element luciferase reporter following treatment with glucose analogs alone, and in combination with SB202190. Induction of cleaved poly(ADP-ribose) polymerase (PARP) was measured by Western blot in the MIA PaCa-2 cells. In vitro anti-proliferative activity of 2-DG and D-allose alone, or in combination with oxaliplatin (pancreatic cell lines), cisplatin (ovarian cell lines), or with SB202190 were investigated using the MTT assay. Results: SB202190 decreased HIF-1α protein accumulation and transcriptional activity. 2-DG demonstrated greater anti-proliferative activity than D-allose. Pre-treatment with SB202190 enhanced activity of both 2-DG and D-allose in MIA PaCa-2, BxPC-3, ASPC-1, and SK-OV-3 cells. The combination of D-allose and platinum agents was additive to moderately synergistic in all but the OVCAR-3 and HEY cells. SB202190 pre-treatment further enhanced activity of D-allose and 2-DG with platinum agents in most cell lines investigated. Conclusions: SB202190 induced sensitization of tumor cells to 2-DG and D-allose may be partially mediated by inhibition of HIF-1α activity. Combining glucose analogs and p38 MAPK inhibitors with chemotherapy may be an effective approach to target glycolytic tumor phenotypes. [ABSTRACT FROM AUTHOR]

The first analytical method is presented for the identification and absolute configuration determination of all 24 aldohexose and 2-ketohexose isomers, including the D and L enantiomers for allose, altrose, galactose, glucose, gulose, idose, mannose, talose, fructose, psicose, sorbose, and tagatose. Two unique fixed ligand kinetic method combinations were discovered to create significant enough energetic differences to achieve chiral discrimination among all 24 hexoses. Each of these 24 hexoses yields unique ratios of a specific pair of fragment ions that allows for simultaneous determination of identification and absolute configuration. This mass spectrometric-based methodology can be readily employed for accurate identification of any isolated monosaccharide from an unknown biological source. This work provides a key step towards the goal of complete de novo carbohydrate analysis. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The present study investigates the neuroprotective effects of d -allose, a rare sugar, against ischemia/reperfusion injury in a gerbil model. Transient forebrain ischemia was induced by occlusion of the bilateral common carotid arteries for 5 min. d -Allose was intravenously injected before and after ischemia (200 mg/kg). Extracellular glutamate and lactate release from the gerbil brain, and PO 2 profiles were monitored during ischemia and reperfusion. We also examined neuronal death and oxidative damage in the hippocampus one week after ischemia reperfusion, and investigated functional outcome. d -Allose administration suppressed glutamate and lactate release compared to vehicle controls. Brain damage, 8-OHdG levels (a marker of oxidative stress) and locomotor activities were significantly decreased by d -allose treatment. The present results suggest that d -allose reduces delayed neuronal death and behavioral deficits after transient ischemia by changing cerebral metabolism and inhibiting oxidative stress. [ABSTRACT FROM AUTHOR]

The article presents a study that examines the anti-proliferative activites of 6-O-acyI-D-allose against the human leukemia MOLT-4F cell line. It describes the method of the study that observes the derivatives of the 6-O-acyI-D-allose which occurred in a furanose form. It also outlines the result of the study which indicates that 6-O-acyI-D-alloses have anti-proliferative effect on human leukemia MOLT-4F cells.

Only d-allose, among various rare monosaccharides tested, induced resistance to Xanthomonas oryzae pv. oryzae in susceptible rice leaves with defence responses: reactive oxygen species, lesion mimic formation, and PR-protein gene expression. These responses were suppressed by ascorbic acid or diphenylene iodonium. Transgenic rice plants overexpressing OsrbohC, encoding NADPH oxidase, were enhanced in sensitivity to d-allose. d-Allose-mediated defence responses were suppressed by the presence of a hexokinase inhibitor. 6-Deoxy-d-allose, a structural derivative of d-allose unable to be phosphorylated, did not confer resistance. Transgenic rice plants expressing Escherichia coli AlsK encoding d-allose kinase to increase d-allose 6-phosphate synthesis were more sensitive to d-allose, but E. coli AlsI encoding d-allose 6-phosphate isomerase expression to decrease d-allose 6-phosphate reduced sensitivity. A d-glucose 6-phosphate dehydrogenase-defective mutant was also less sensitive, and OsG6PDH1 complementation restored full sensitivity. These results reveal that a monosaccharide, d-allose, induces rice resistance to X. oryzae pv. oryzae by activating NADPH oxidase through the activity of d-glucose 6-phosphate dehydrogenase, initiated by hexokinase-mediated conversion of d-allose to d-allose 6-phosphate, and treatment with d-allose might prove to be useful for reducing disease development in rice. [ABSTRACT FROM AUTHOR]

Background: Recently, one of the rare sugars, D-allose, has received attention from many researchers because of its availability for mass production and its various physiological functions. Among these, an antioxidative effect has been strongly suggested. In this study, we investigated whether this effect is also applicable to the field of skin surgery. Methods: In ischemia-reperfusion injury model using the rat abdominal skin island flap (male Wistar rats, n = 110), D-allose was injected intravenously 15 min before 8-h ischemia. The survival area (%) was measured by digital photographic assessment 1 wk after surgery, and multiple comparisons (Fisher's protected least significant difference) were carried out. Histopathological examination (neutrophilic infiltration into dermis in hematoxylin and eosin stain) and immunostaining (of ectodermal dysplasia-1 (ED1)-positive cells/flap) were assessed. Myeloperoxidase (MPO) activity in the skin flap (sampling at the time of 8 h after reperfusion) was measured spectrophotometrically, and Student t-test was performed. Results: D-allose extended the survival of the remaining flaps, and a dose greater than 30 mg (0.1 mg/g) was necessary to be effective. The flap survival rates in the 30, 60, and 150 mg groups were significantly higher than that in the control (saline) group: 75.87 ± 5.90, 79.27 ± 7.81, and 77.87 ± 6.20 versus 50.53 ± 9.66, respectively (P < 0.05). ED1-positive cells/flap in 60 mg of D-allose and control (saline) were 78 ± 25.7 versus 124 ± 15.8, respectively (P = 0.08). The MPO activity in the D-allose 60 mg group was 0.40 ± 0.04, and that in the control (saline) was 0.72 ± 0.12. D-allose significantly reduced the skin tissue MPO activity (P < 0.05) compared with that in the control (saline) group. Conclusions: We proved that D-allose has a reducing effect against ischemia-reperfusion injury on the skin island flap model, and the mechanism is related to inhibiting the activity of neutrophils in the skin tissues. Compared with chemo-synthetic materials, rare sugars are safer for our bodies as well as the environment; therefore, this rare sugar project is expected to lead to the development of a safer antioxidant for skin flap surgery. [ABSTRACT FROM AUTHOR]

Highlights: [•] Multigram syntheses of carbohydrate-based spirooxazolidinones are developed. [•] Novel 3-spiropseudonucleosides are characterized by X-ray diffraction analysis. [•] User-friendly diacetone-α-d-glucose oxidation is elaborated and validated. [Copyright &y& Elsevier]

Abstract: Background: A metabolomic approach using umbilical cord blood from infants at birth has not been studied widely yet. Aim: We examined changes in metabolite levels in umbilical cord blood at birth via gas chromatography/mass spectrometry (GC/MS)-based metabolomics, with the aim of achieving a detailed understanding of fetal stress during labor. Study design: All procedures were reviewed and approved by the Institutional Review Board of Kobe University School of Medicine. This was a cohort study of pregnant women based in Palmore Hospital, which is located in an urban area of Japan, and was carried out between December 2010 and May 2011. Subject: Umbilical cord arterial blood samples were obtained from 41 infants immediately after delivery. Outcome measures: Metabolites in the blood samples were measured using GC/MS to investigate whether the delivery method (spontaneous onset of labor, induction of labor or elective cesarean section) affected the metabolite profile in umbilical cord blood. Results: Elective cesarean section without labor led to lower levels of isoleucine, fructose, mannose, glucose, allose, glucuronic acid, inositol and cysteine in comparison with vaginal delivery following spontaneous labor and without medication. Conclusion: It is proposed that the stress associated with labor be involved in alterations in the levels of metabolites, particularly saccharides such as glucose, in umbilical cord blood. [Copyright &y& Elsevier]

We previously reported that a rare sugar d-allose, which is the d-glucose epimer at C3, inhibits the gibberellin-dependent responses such as elongation of the second leaf sheath and induction of α-amylase in embryo-less half seeds in rice (Fukumoto et al. ). d-Allose suppresses expressions of gibberellin-responsive genes downstream of SLR1 protein in the gibberellin-signaling through hexokinase (HXK)-dependent pathway. In this study, we discovered that d-allose induced expression of ABA-related genes including OsNCED1- 3 and OsABA8ox1- 3 in rice. Interestingly, d-allose also up-regulated expression of OsABF1, encoding a conserved bZIP transcription factor in ABA signaling, in rice. The d-allose-induced expression of OsABF1 was diminished by a hexokinase inhibitor, d-mannoheptulose (MNH). Consistently, d-allose also inhibited Arabidopsis growth, but failed to trigger growth retardation in the glucose- insensitive2 ( gin2) mutant, which is a loss-of-function mutant of the glucose sensor AtHXK1. d-Allose activated AtABI5 expression in transgenic gin2 over-expressing wild-type AtHXK1 but not in gin2 over-expressing the catalytic mutant AtHXK1, indicating that the d-allose phosphorylation by HXK to d-allose 6-phosphate (A6P) is the first step for the up-regulation of AtABI5 gene expression as well as d-allose-induced growth inhibition. Moreover, overexpression of OsABF1 showed increased sensitivity to d-allose in rice. These findings indicated that the phosphorylation of d-allose at C6 by hexokinase is essential and OsABF1 is involved in the signal transduction for d-allose-induced growth inhibition. [ABSTRACT FROM AUTHOR]

Unusual deoxy sugars are often attached to natural products such as antibiotics, antifungals, and chemotherapeutic agents. One such sugar is mycinose, which has been found on the antibiotics chalcomycin and tylosin. An intermediate in the biosynthesis of mycinose is dTDP-6-deoxy-d-allose. Four enzymes are required for the production of dTDP-6-deoxy-d-allose in Streptomyces bikiniensis, a soil-dwelling microbe first isolated from the Bikini and Rongelap atolls. Here we describe a combined structural and functional study of the enzyme ChmJ, which reportedly catalyzes the third step in the pathway leading to dTDP-6-deoxy-d-allose formation. Specifically, it has been proposed that ChmJ is a 3′-epimerase that converts dTDP-4-keto-6-deoxyglucose to dTDP-4-keto-6-deoxyallose. This activity, however, has never been verified in vitro. As reported here, we demonstrate using 1H nuclear magnetic resonance that ChmJ, indeed, functions as a 3′-epimerase. In addition, we determined the structure of ChmJ complexed with dTDP-quinovose to 2.0 Å resolution. The structure of ChmJ shows that it belongs to the well-characterized “cupin” superfamily. Two active site residues, His 60 and Tyr 130, were subsequently targeted for study via site-directed mutagenesis and kinetic analyses, and the three-dimensional architecture of the H60N/Y130F mutant protein was determined to 1.6 Å resolution. Finally, the structure of the apoenzyme was determined to 2.2 Å resolution. It has been previously suggested that the position of a conserved tyrosine, Tyr 130 in the case of ChmJ, determines whether an enzyme in this superfamily functions as a mono- or diepimerase. Our results indicate that the orientation of the tyrosine residue in ChmJ is a function of the ligand occupying the active site cleft. [ABSTRACT FROM AUTHOR]

Although -glucose increased the root growth of Arabidopsis seedlings, -allose (a -glucose epimer at the third carbon atom) inhibited the root growth at concentrations >0.1 mmol L and the inhibition increased with increasing -allose concentrations. Allitol (a reduction product of -allose) did not show any significant effect on the growth. The addition of -glucose into the growth medium of Arabidopsis reversed the -allose-induced growth inhibition, which suggests that the inhibition is not caused by the toxicity of the accumulation of -allose and/or its metabolites in the seedlings. -Allose is phosphorylated by hexokinase, using ATP and phosphate, to allose-6-phosphate, with no known capacity for further metabolism. The addition of phosphate into the growth medium did not affect the -allose-induced growth inhibition and -allose did not reduce the ATP level in the roots. These results suggest that the inhibition is not due to phosphate starvation and ATP depletion. -Mannoheptulose, a specific competitive inhibitor of hexokinase, defeated the -allose-induced growth inhibition. Hexokinase is known to have a sugar-sensing function and possibly triggers a signal cascade, resulting in the change of several gene expressions. Therefore, the phosphorylation of -allose by hexokinase might trigger a signal cascade, resulting in the inhibition of Arabidopsis root growth. This is probably a useful model system for studies of the hexokinase-mediated sugar-sensing function and for developing new types of weed-control agents. [ABSTRACT FROM AUTHOR]

Abstract: One hundred and two conformations of α- and β-d-allopyranose, the C-3 substituted epimer of glucopyranose, were geometry optimized using the density functional, B3LYP, and the basis set, 6-311++G∗∗. Full geometry optimization was performed on different ring geometries and on the hydroxymethyl rotamers (gg/gt/tg). Analytically derived Hessians were used to calculate zero point energy, enthalpy, and entropy. The lowest energy and free energy conformation found is the α-tg(g−)-4 C 1-c conformation, which is only slightly higher in electronic (∼0.2kcal/mol) and free energy than the lowest energy α-d-glucopyranose. The in vacuo calculations showed a small (∼0.3kcal/mol) energetic preference for the α- over the β-anomer for allopyranose in the 4 C 1 conformation, whereas in the 1 C 4 conformation a considerable (∼1.6kcal/mol) energetic preference for the β- over the α-anomer for allopyranose was encountered. The results are compared to previous aldohexose calculations in vacuo. Boat and skew forms were found that remained stable upon gradient optimization although many starting boat conformations moved to other skew forms upon optimization. As found for glucose, mannose, and galactose the orientation and interaction of the hydroxyl groups make the most significant contributions to the conformation/energy relationship in vacuo. A comparison of different basis sets and density functionals is made in the Discussion section, confirming the appropriateness of the level of theory used here. [Copyright &y& Elsevier]

The C‐glycoside of methyl α‐d‐altropyranosyl‐(1→4)‐α‐d‐glucopyranoside 2 was prepared in a convergent fashion, from readily available precursors, 4‐O‐tert‐butyldiphenylsilyl‐1,2‐O‐isopropylidene‐d‐erythro‐S‐phenyl monothiohemiacetal 13 (five steps from D‐ribose) and the known acid, methyl 2,3,6‐tri‐O‐benzyl‐4‐C‐(carboxymethyl)‐4‐deoxy‐α‐d‐glucopyranoside 17 (seven steps from methyl α‐d‐glucopyranoside). The key reactions in the synthesis are the oxocarbenium ion cyclization of thioacetal‐enol ether 19 to a C1 substituted glycal 20, and the stereoselective hydroboration of 20 to the α‐C‐altroside 21. †This paper is Dedicated to Professor Gérard Decotes on the occasion of his 70th birthday. [ABSTRACT FROM AUTHOR]