Identification of a novel recombinant D-lyxose isomerase from Thermoprotei archaeon with high thermostable, weak-acid and nickel ion dependent properties.

Recently, production of D-mannose becomes a hotspot owing to it exhibiting many physiological functions on people's health and wide applications in food and pharmaceutical field. The use of biological enzymes to production of D-mannose is of particular receiving considerable concerns due to it possessing many merits over chemical synthesis and plant extraction strategies. D-Lyxose isomerase (D-LIase) plays a pivotal role in preparation of D-mannose from d-fructose through isomerization reaction. Thus, a novel putative D-LIase from thermophiles strain Thermoprotei archaeon which was expressed in E. coli BL21(DE3) was first identified and biochemically characterized. The recombinant D-LIase showed an optimal temperature of 80 and 85 °C and pH of 6.5. It was highly thermostable at 70 °C and 80 °C after incubating for 48 h and 33 h, respectively, with retaining over 50% of the initial activity. A lower concentration of Ni2+ (0.5 mM) could greatly increase the activity by 25-fold, which was rare reported in other D-LIases. It was a dimer structure with melting temperature of 88.3 °C. Under the optimal conditions, 15.8 g L-1 of D-mannose and 33.8 g L-1 of D-xylulose were produced from 80 g L-1 of d-fructose and D-lyxose, respectively. This work provided a promising candidate sugar isomerase T. archaeon D-LIase for the production of D-mannose and D-xylulose.

Characterization of a recombinant l-ribose isomerase from Mycetocola miduiensis and its application for the production of l-ribulose.

An enzyme, l-ribose isomerase (l-RI), mostly catalyzes the isomerization of l-ribose and l-ribulose. These so-called rare sugars are essential for the treatment of cancer and other viral diseases. In the present study, l-ribose isomerase produced from a bacterium, Mycetocola miduiensis (Mm-LRIse), by using l-ribose as a carbon source. The recombinant l-ribose isomerase gene was cloned and overexpressed from M. miduiensis and purified with an exclusive band of 32 kDa by nickel-affinity chromatography. This gene possessed 267 amino acids protein having an estimated molecular weight of 29,568.17 Da. The native molecular weight of Mm-LRIse estimated by HPLC was 134.84 kDa. The recombinant l-ribose isomerase was highly active in sodium phosphate (50 mM) buffer at 40 °C and pH 7.5, showing the specific activity up to 47.40 U mg-1. Mm-LRIse showed no significant enhancement in activity with metallic ions except Mn2+ and Co2+. The values of Km, Kcat, Kcat/Km and Vmax of Mm-LRIse against l-ribose substrate were 42.48 mM, 9259.26 min-1, 217.43 min-1 mM-1, and 277.78 U mg-1 respectively. At equilibrium, the l-ribulose transformation rate was nearly 32 % (6.34 g L-1) using 20 g L-1 of l-ribose. The results revealed that the Mm-LRIse enzyme has a potential for L-ribulose production from l-ribose.

Timely Addition of Glutathione for Its Interaction with Deoxypentosone To Inhibit the Aqueous Maillard Reaction and Browning of Glycylglycine-Arabinose System.

The inhibitory effects of glutathione (GSH) and oxiglutathione (GSSG) on Maillard browning were compared, and it was clarified that free sulfhydryl was the key substance for the inhibition. The Amadori rearrangement product (ARP) derived from glycylglycine (Gly-Gly) and arabinose (Ara) was prepared by aqueous Maillard reaction, and LC-MS/MS was used to investigate the reaction products of GSH and purified ARP. Reaction between GSH and deoxypentosone (DP) was found to alter the pathway of aqueous Maillard reaction, which reduced the production of glyoxal, methylglyoxal, and furfural and thereby inhibited the formation of melanoidins. To determine the optimal conditions for browning inhibition, a stepwise increase of temperature was used to prepare Maillard reaction products (MRPs). The results showed that the optimum browning inhibitory effect was obtained by adding GSH after Gly-Gly and Ara heating at 80 °C for 60 min.

Ab-initio and experimental study of pentose sugar dehydration mechanism in the gas phase.

In this work pentose sugar (D-xylose, D-ribose and D-arabinose) gas phase dehydration reaction was investigated by means of mass spectrometric techniques and theoretical calculations. The ionic species derived from the dehydration reaction of protonated D-ribose and D-arabinose were structurally characterized by their fragmentation patterns and the relative dehydration energies measured by energy resolved CAD mass spectra. The results were compared with those recently obtained for D-xylose in the same mass spectrometric experimental conditions. Dehydration of C1-OH protonated sugars was theoretically investigated at the CCSD(T)/cc-pVTZ//M11/6-311++G(2d,2p) level of theory. Protonated pentoses are not stable and promptly lose a water molecule giving rise to the dehydrated ions at m/z 133. D-xylose, D-ribose and D-arabinose dehydration follows a common reaction pathway with ionic intermediates and transition states characterized by similar structures. Slightly different dehydration energies were experimentally measured and the relative trend was theoretically confirmed. The overall dehydration activation energy follows the order arabinose < ribose < xylose. Gas-phase pentose sugar dehydration leads to the formation of protonated 2-furaldehyde as final product. Based on the experimental and theoretical evidence a new mechanistic hypothesis starting from C1-OH protonation was proposed.

Reactions between methylglyoxal and its scavengers in-vivo appear to be catalyzed enzymatically.

Methylglyoxal (MGO) is thought to be an important contributor to the development of diabetic complications. In this paper I propose that MGO, not detoxified by the glyoxalase system, is removed from circulation by MGO-scavengers. Furthermore, since intrinsic rates of reactions between MGO and its scavengers are low, I propose that, in-vivo, these reactions are catalyzed enzymatically.

Azido Pentoses: A New Tool To Efficiently Label Mycobacterium tuberculosis Clinical Isolates.

Mycobacterium tuberculosis (Mtb), the main causative agent of tuberculosis (Tb), has a complex cell envelope which forms an efficient barrier to antibiotics, thus contributing to the challenges of anti-tuberculosis therapy. However, the unique Mtb cell wall can be considered an advantage and be utilized to selectively label Mtb bacteria. Here we introduce three azido pentoses as new compounds for metabolic labeling of Mtb: 3-azido arabinose (3AraAz), 3-azido ribose (3RiboAz), and 5-azido arabinofuranose (5AraAz). 5AraAz demonstrated the highest level of Mtb labeling and was efficiently incorporated into the Mtb cell wall. All three azido pentoses can be easily used to label a variety of Mtb clinical isolates without influencing Mtb-dependent phagosomal maturation arrest in infection studies with human macrophages. Thus, this metabolic labeling method offers the opportunity to attach desired molecules to the surface of Mtb bacteria in order to facilitate investigation of the varying virulence characteristics of different Mtb clinical isolates, which influence the outcome of a Tb infection.

Selenofuranoside Ameliorates Memory Loss in Alzheimer-Like Sporadic Dementia: AChE Activity, Oxidative Stress, and Inflammation Involvement.

Alzheimer's disease (AD) is becoming more common due to the increase in life expectancy. This study evaluated the effect of selenofuranoside (Se) in an Alzheimer-like sporadic dementia animal model. Male mice were divided into 4 groups: control, Aß, Se, and Aß + Se. Single administration of Aß peptide (fragments 25-35; 3 nmol/3 µL) or distilled water was administered via intracerebroventricular (i.c.v.) injection. Selenofuranoside (5 mg/kg) or vehicle (canola oil) was administered orally 30 min before Aß and for 7 subsequent days. Memory was tested through the Morris water maze (MWM) and step-down passive-avoidance (SDPA) tests. Antioxidant defenses along with reactive species (RS) were assessed. Inflammatory cytokines levels and AChE activity were measured. SOD activity was inhibited in the Aß group whereas RS were increased. AChE activity, GSH, and IL-6 levels were increased in the Aß group. These changes were reflected in impaired cognition and memory loss, observed in both behavioral tests. Se compound was able to protect against memory loss in mice in both behavioral tests. SOD and AChE activities as well as RS and IL-6 levels were also protected by Se administration. Therefore, Se is promising for further studies.

Coumarins hinged directly on benzimidazoles and their ribofuranosides to inhibit hepatitis C virus.

A new compound library that contained 20 hinged benzimidazole-coumarin hybrids and their ß-d-ribofuranosides was established. The anti-hepatitis C virus (HCV) activity of all novel coumarin derivatives, which were obtained by use of organic synthetic methods, was tested. Two of these hybrids exhibited appealing EC50 values of as low as 3.0 and 5.5 µM. The best selectivity index was 14. The incorporation of a d-ribofuranose into the hinged hybrids provided the corresponding nucleosides with the ß configuration, one of which inhibited HCV replication with an EC50 value of 20 µM. Additionally, the structure-activity relationship is elucidated on the basis of the functional groups that were attached to the nuclei of benzimidazole, coumarin, and ribofuranose of the hybrids.

Effect of amide-triazole linkers on the electrochemical and biological properties of ferrocene-carbohydrate conjugates.

Amide-triazole linker incorporated ferrocene-carbohydrate conjugates were prepared by adopting a regiospecific copper(II)-catalysed 1,3-cycloaddition of ferrocenoyl propargylamide and isopropylidene/acetyl protected carbohydrate azides. Hydrophilic ferrocene glycoside with an amide-triazole linker was synthesised by deacetylation of the hydroxyl groups. All the new compounds were characterised by UV-visible and electrochemical studies and they were found to be stable in organic solvents as well as in the buffer system under physiological conditions (pH = 7.0). The diffusion coefficient (D(f)) of the conjugates was also calculated by means of cyclic voltammetric studies. It was observed that while the molecular weight of the compounds had no significant effect on the diffusion coefficient, the hydrophobic/hydrophilic nature of the carbohydrate scaffold displayed varied diffusion coefficient values. Stabilization of the compounds in buffer solution under physiological pH led to almost identical diffusion coefficient values. The compounds derived from xylose and ribose exhibited cytotoxicity on hormone-dependent and hormone-independent breast cancer cell lines, whereas the conjugates derived from glucose and galactose were found to be non-toxic in nature. The compounds did not show any antimicrobial activity against Gram-positive and Gram-negative pathogens.

Correlating changes that occur in chemical properties with the generation of antioxidant capacity in different sugar-amino acid Maillard reaction models.

UNLABELLED: We investigated the development of antioxidant activity relative to the change of pH, fluorescent intensity, ultraviolet (UV) absorbance (A294), browning (A420), and alpha-dicarbonyl compounds in sugar-amino acid Maillard reaction (MR) model systems comprising fructose, glucose, or ribose each with glycine (Fru-Gly, Glu-Gly, and Rib-Gly) or lysine (Fru-Lys, Glu-Lys, and Rib-Lys), respectively, which were heated at 121 °C for 5 to 90 min. For hexose models, the change in pH was shown to fit a second-order polynomial regression with A294 and A420. Antioxidant activity was significantly and positively correlated with UV absorbance (r = 0.905, P < 0.001) and browning products (r = 0.893, P < 0.001) rather than with fluorescent products or the alpha-dicarbonyl compounds. Type of sugar was most important in evoking a change in UV absorbance, browning, alpha-dicarbonyl compounds, and antioxidant activity of MR products (MRPs). In conclusion, the antioxidant activity of MRPs in six model systems was more closely associated with products derived at the intermediate-to-late stages of the reaction and influenced mostly by the type of sugar. PRACTICAL APPLICATION: We report on the different factors and their interactions that are important for understanding the functional attributes of food components that comprise the generation of Maillard browning products and the associated antioxidant activities generated during high-temperature food processing.

Polyphosphates and pyrophosphates of pentopyranoses and pentofuranoses as allosteric effectors of human hemoglobin: synthesis, molecular recognition, and oxygen release.

Perphosphorylated pentopyranoses and pentofuranoses were synthesized from parent carbohydrates as potential allosteric effectors of hemoglobin (Hb). The construction of seven- and eight-membered cyclic pyrophosphates was also carried out successfully on most of the pentoses. All final compounds were tested for their efficiency on oxygen release from human Hb. Most proved to be efficient allosteric effectors, some of them with an affinity toward Hb and an effect on oxygen release from Hb approaching that of myo-inositol hexakisphosphate, which is one of the most active allosteric effectors of Hb. The efficacy was higher for free phosphates than for pyrophosphates.

Alcohol-, diol-, and carbohydrate-substituted indenoisoquinolines as topoisomerase I inhibitors: investigating the relationships involving stereochemistry, hydrogen bonding, and biological activity.

The DNA-relaxing enzyme topoisomerase I (Top1) can be inhibited by heterocyclic compounds such as indolocarbazoles and indenoisoquinolines. Carbohydrate and hydroxyl-containing side chains are essential for the biological activity of indolocarbazoles. The current study investigated how similar functionalities could be "translated" to the indenoisoquinoline system and how stereochemistry and hydrogen bonding affect biological activity. Herein is described the preparation and assay of indenoisoquinolines substituted with short-chain alcohols, diols, and carbohydrates. Several compounds (including those derived from sugars) display potent Top1 poisoning and antiproliferative activities. The Top1 poisoning activity of diol-substituted indenoisoquinolines is dependent upon stereochemistry. Although the effect is striking, molecular modeling and docking studies do not indicate any reason for the difference in activity due to similar calculated interactions between the ligand and Top1-DNA complex and ambiguity about the binding mode. A stereochemical dependence was also observed for carbohydrate-derived indenoisoquinolines. Although similar trends were observed in other classes of Top1 inhibitors, the exact nature of this effect has yet to be elucidated.

Stereoselective syntheses of pentose sugars under realistic prebiotic conditions.

Glycolaldehyde and DL-glyceraldehyde reacted in a water-buffered solution under mildly acidic conditions and in the presence of chiral dipeptide catalysts produced pentose sugars whose configuration is affected by the chirality of the catalyst. The chiral effect was found to vary between catalysts and to be largest for di-valine. Lyxose, arabinose, ribose and xylose are formed in different amounts, whose relative proportions do not change significantly with the varying of conditions. With LL-peptide catalysts, ribose was the only pentose sugar to have a significant D-enantiomeric excess (ee) (

Characterization of aldolase from Methanococcus jannaschii by gas chromatography.

The products of reactions catalyzed by Methanococcus. jannaschii (Mj) aldolase using various substrates were identified by gas chromatography (GC). Although Mj aldolase is considered a fuculose-1-phosphate aldolase based on homology searching after gene sequencing, it has not been proven to be a fuculose-1-phosphate aldolase based on its reaction products. Mj aldolase was found to catalyze reactions between glycoaldehyde or D, L-glyceraldehyde and DHAP (dihydroxyacetone phosphate). Before performing GC the ketoses produced were converted into peracetylated alditol derivatives by sequential reactions, i.e., dephosphorylation, NaBH(4) reduction, and acetylation. By comparing the GC data of final products with those of standard alditol samples, it was found that the enzymatic reactions with glycoaldehyde, D-glyceraldehyde, and D, L-glyceraldehyde produced D-ribulose-1-phosphate, D-psicose-1-phosphate, and a mixture of D-psicose and L-tagatose-1-phosphate, respectively. These results provide direct evidence that Mj aldolase is a fuculose-1-phosphate aldolase.

Simple synthesis and anti-HIV activity of novel 3'-vinyl branched apiosyl pyrimidine nucleosides.

Novel vinyl branched apiosyl nucleosides were synthesized in this study. Apiosyl sugar moiety was constructed by sequential ozonolysis and reductions. The bases (uracil and thymine) were efficiently coupled by glycosyl condensation procedure (persilyated base and TMSOTf). The antiviral activities of the synthesized compounds were evaluated against the HIV-1, HSV-1, HSV-2, and HCMV. Compound 10beta displayed moderate anti-HIV activity (EC50 = 17.3 microg/mL) without exhibiting any cytotoxicity up to 100 microM.

Deciphering indolocarbazole and enediyne aminodideoxypentose biosynthesis through comparative genomics: insights from the AT2433 biosynthetic locus.

AT2433, an indolocarbazole antitumor antibiotic, is structurally distinguished by its aminodideoxypentose-containing disaccharide and asymmetrically halogenated N-methylated aglycon. Cloning and sequence analysis of AT2433 gene cluster and comparison of this locus with that encoding for rebeccamycin and the gene cluster encoding calicheamicin present an opportunity to study the aminodideoxypentose biosynthesis via comparative genomics. The locus was confirmed via in vitro biochemical characterization of two methyltransferases--one common to AT2433 and rebeccamycin, the other unique to AT2433--as well as via heterologous expression and in vivo bioconversion experiments using the AT2433 N-glycosyltransferase. Preliminary studies of substrate tolerance for these three enzymes reveal the potential to expand upon the enzymatic diversification of indolocarbazoles. Moreover, this work sets the stage for future studies regarding the origins of the indolocarbazole maleimide nitrogen and indolocarbazole asymmetry.

Neutral pentosides surfactants issued from the butadiene telomerization with pentoses: preparation and amphiphilic properties.

Interfacial properties of octadienyl pentosides prepared by the palladium-catalyzed telomerization of butadiene with free pentoses have been evaluated and compared to those of mixtures issued from the autoclaving process.

The antituberculosis, antitumor, multibranched dodecafuranoarabinan of Mycobacterium species has been assembled from a single n-pentenylfuranoside source.

An n-pentenyl furanosyl-1,2-orthoester can function as a donor or be rearranged leading to an n-pentenyl furanoside acceptor which is glycosylated by its progenitor, regioselectively or doubly, thereby enabling rapid fabrication of a multibranched dodecasaccharide, known to possess a wide variety of biological interactions.

Expeditious synthesis of enantiopure symmetrical macroheterocycles by ring-closing metathesis of ether and tether-linked 1,2-O-isopropylidenefuranosides.

Bis-olefinic symmetrical carbohydrate derivatives were prepared by joining two 1,2-O-isopropylidenefuranose units either through an ether linkage or by a tether of variable size. The ring-closing metathesis (RCM) of these substrates using Grubbs' first-generation catalyst led to the synthesis of enantiopure symmetrical macroheterocycles containing nine- to twenty-five-membered rings fused to the 1,2-O-isopropylidenefuranose ring.