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1.
3-O-β-d-Xylopyranosyl-l-serine (xylosylserine) was synthesized by the following three-step procedure: 1) 2,3,4-tri-O-benzoyl-α-d-xylopyranosyl bromide (benzobromoxylose) was condensed withN-carbobenzoxy-l-serine benzyl ester using the silver triflate-collidine complex as promoter; 2) theN-carbobenzoxy and benzyl ester groups in the resultant glycoside were cleaved by transfer hydrogenation with palladium black as catalyst and ammonium formate as hydrogen donor; and 3) the benzoyl groups were removed with methanolic ammonia. Xylosylserine was obtained in an overall yield of 70%. O-β-d-Galactopyranosyl-(1-4)-O-β-d-xylopyranosyl-(1-3)-l-serine (galactosylxylosylserine) was also synthesized by this methodology and was characterized by 2-dimensional (2D) NMR spectroscopy techniques. The two serine glycosides (xylosylserine and galactosylxylosylserine) were used in detection and partial purification of galactosyltransferase I (UDP-d-galactose:d-xylose galactosyltransferase) from adult rat liver.  相似文献   

2.
The tetrasaccharide 2-(p-trifluoroacetamidophenyl)ethylO-α-l-fucopyranosyl-(1–3)-O-(2-acetamido-2-deoxy-β-d-glucopyranosyl)-(1–3)-O-β-d-galactopyranosyl-(1–4)-β-d-glucopyranoside was synthesized from thioglycoside intermediates. The key step was a methyl triflate promoted glycosidation of a lactose-derived 3′,4′-diol with a disaccharide thioglycoside to give a β(1–3)-linked tetrasaccharide derivative in 67% yield.  相似文献   

3.
Chemical investigation of the freshwater rhodophyte microalga Porphyridium aerugineum led to the isolation of five new galactolipids, namely, (2S)-1-O-eicosapentaenoyl-2-O-arachidonoyl-3-O-β-d-galactopyranosylglycerol (1), (2S)-1-O-eicosapentaenoyl-2-O-linoleoyl-3-O-β-d-galactopyranosylglycerol (2), (2S)-1-O-arachidoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (6), (2S)-1-O-eicosapentaenoyl-2-O-arachidoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (7), and (2S)-1-O-eicosapentaenoyl-2-O-linoleoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (8) together with five known galactolipids. The stereo-structures of all new galactolipids were elucidated by spectroscopic analyses and both enzymatic and chemical degradation methods. This is the first report of galactolipids from P. aerugineum. The newly isolated galactolipids showed strong and dose-dependent nitric oxide (NO) inhibitory activity against lipopolysaccharide-induced NO production in RAW264.7 macrophage cells. Both galactolipids 1 and 2 possessed stronger NO inhibitory activity than N G-methyl-l-arginine acetate salt, a well-known NO inhibitor used as a positive control. Further study suggested that these galactolipids inhibit NO production through downregulation of inducible nitric oxide synthase expression.  相似文献   

4.
Chemical investigation of a marine microalga, Nannochloropsis granulata, led to the isolation of four digalactosyldiacylglycerols namely, (2S)-1-O-eicosapentaenoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (1), (2S)-1-O-eicosapentaenoyl-2-O-palmitoleoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (2), (2S)-1-O-eicosapentaenoyl-2-O-myristoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (3), and (2S)-1,2-bis-O-eicosapentaenoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (4), together with their monogalactosyl analogs (58). Among the isolated galactolipids 2 and 3 were new natural products. Complete stereochemistry of 1, 4, 5, 7, and 8 was determined for the first time by both spectroscopic techniques and classical degradation methods. Both mono- and digalactosyldiacylglycerols isolated from N. granulata possessed strong nitric oxide (NO) inhibitory activity against lipopolysaccharide-induced NO production in RAW264.7 macrophage cells through downregulation of inducible nitric oxide synthase expression indicating the possible use as anti-inflammatory agents.  相似文献   

5.
Selected eight yeast strains isomerized-glycero-d-galacto-heptose tod-manno-heptulose. The conversion is 7–10%. Under identical conditions, the reverse isomerization ofd-manno-heptulose tod-glycero-d-galacto-heptose ord-glycero-d-talo-heptose does not take place.  相似文献   

6.
A MeOH extract of cultivated Chondrus crispus showed dose-dependent nitric oxide (NO) inhibition of lipopolysaccharide-induced NO production in macrophage RAW264.7 cells. NO inhibition-guided fractionation of the extract led to identification of eicosapentaenoic acid (EPA, 1), arachidonic acid (AA, 2), lutein (3), and eight galactolipids as active components. Based on spectral analysis, the isolated galactolipids were identified as (2S)-1,2-bis-O-eicosapentaenoyl-3-O-β-d-galactopyranosylglycerol (4), (2S)-1-O-eicosapentaenoyl-2-O-arachidonoyl-3-O-β-d-galactopyranosylglycerol (5), (2S)-1-O-(6Z,9Z,12Z,15Z-octadecatetranoyl)-2-O-palmitoyl-3-O-β-d-galactopyranosylglycerol (6), (2S)-1-O-eicosapentaenoyl-2-O-palmitoyl-3-O-β-d-galactopyranosylglycerol (7), (2S)-1,2-bis-O-arachidonoyl-3-O-β-d-galactopyranosylglycerol (8), (2S)-1-O-arachidonoyl-2-O-palmitoyl-3-O-β-d-galactopyranosylglycerol (9), (2S)-1-O-eicosapentaenoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (10), and (2S)-1-O-arachidonoyl-2-O-palmitoyl-3-O-(β-d-galactopyranosyl-6-1α-d-galactopyranosyl)-glycerol (11). All the isolated compounds showed significant NO inhibitory activity. This is the first report of the isolation and identification of individual galactolipids from C. crispus. Moreover, (2S)-1,2-bis-O-arachidonoyl ?3-O-β-d-galactopyranosylglycerol (8) is a novel compound.  相似文献   

7.
A novel protodioscin-(steroidal saponin)-glycoside hydrolase, named protodioscin-glycosidase-1 (PGase-1), was purified and characterized from the Aspergillus oryzae strain. The molecular mass of this enzyme was determined to be about 55 kDa based on SDS-polyacrylamide gel electrophoresis. PGase-1 was able to hydrolyze the terminal 26-O-β-d-glucopyranoside of protodioscin (furostanoside) to produce dioscin (spirostanoside), and then further hydrolyze the terminal 3-O-(1?→?4)-α-l-rhamnopyranoside of dioscin to form progenin III. However, PGase-1 could hardly hydrolyze the 3-O-(1?→?2)-α-l-rhamnopyranoside of progenin III, 3-O-β-d-glucoside of trillin, and the 1-O-glycosides of ophiopogonin D (steroidal saponin). In addition, PGase-1 also could hydrolyze the α-d-galactopyranoside, β-d-glucopyranoside, and β-d-galactopyranoside of p-nitrophenyl-glycosides, but the enzyme could not hydrolyze the α-d-mannopyranoside, α-l-arabinopyranoside, α-d-glucopyranoside, β-d-xylopyranoside, and α-l-rhamnopyranoside of p-nitrophenyl-glycosides. These new properties of PGase-1 were significantly different from those of previously described steroidal saponin-glycosidases and the glycosidases currently described in Enzyme Nomenclature by the NC-IUBMB. The gene (termed as pgase-1) encoding PGase-1 was cloned, sequenced, and expressed in Pichia pastoris GS115. The complete nucleotide sequence of pgase-1 consists of 1,725 bp. The recombinant PGase-1 from recombinant P. pastoris GS115 strain also showed the activity hydrolyzing glycosides of steroidal saponins which was similar to that of the wild-type PGase-1 from A. oryzae. The PGase-1 gene is highly similar to Aspergilli α-amylase (EC 3.2.1.1), and PGase-1 should be classified as glycoside hydrolase family 13 by the method of gene sequence-based classification. But the enzyme properties of PGase-1 are different from those of α-amylase in this family.  相似文献   

8.
A pre-embedding lectin-gold labelling method was used to characterize the carbohydrate components in the mucilage ofLemonniera aquatica. A specific tissue processing protocol was developed, namely: a) primary fixation in 2% paraformaldehyde and 0.2% glutaraldehyde in PIPES buffer (pH 7.2) for 30 min; b) secondary fixation in 2% glutaraldehyde in the same buffer system for 1 h; c) post-fixation in 1% aqueous OsO4 for 1h; d) embedment in Möllenhaur's resin. The three gold conjugated lectins used were: concanavalin A, wheat germ agglutinin andLimax flavus agglutinin, allowing detection of their complementary saccharides, namely α-d-mannose/α-d-glucose,N-acetyl-d-glucosamine (GluNAc), andN-acetylneuraminic acid (NANA), respectively.N-Acetyl-d-glucosamine and NANA residues were the major components of germ tube mucilage with only a small amount of α-d-manose/α-d-glucose. However, NANA was restricted to the mucilage in the region of germ tube emergence from the conidial arm. The abundance of GluNAc and NANA residues on hyphae and appressoria was less than that on the germ tube. Conversely, α-d-mannose/α-d-glucose was more abundant in the appressorial mucilage. Variability of mucilage composition was found to exist between different structures of the germinated conidium and also between different regions of the same structure. Further, the conidial cell wall ofL. aquatica is not chitinous, and lacks NANA and α-d-mannose/α-d-gluocse.  相似文献   

9.
10.
A recombinant putative N-acyl-d-glucosamine 2-epimerase from Dictyoglomus turgidum was identified as a cellobiose 2-epimerase by evaluating its substrate specificity. The purified enzyme was a 46?kDa monomer with a specific activity of 16.8?μmol?min?1?mg?1 for cellobiose. The epimerization activity was maximal at pH 7.0 and 70?°C with a half-life of 55?h. The isomerization of the glucose at the reducing end of β-1,4- and α-1,4-linked gluco-oligosaccharides to a fructose moiety by the enzyme took place after the epimerization of the glucose to a mannose moiety. The enzyme converted cellobiose to 12.8?% 4-O-β-d-glucopyranosyl-d-mannose and 54.6?% 4-O-β-d-glucopyranosyl-d-fructose as an equilibrium and converted lactose to 12.8?% epilactose and 54.3?% lactulose.  相似文献   

11.
Astrocytic excitatory amino acid transporters (EAATs) regulate excitatory transmission and limit excitotoxicity. Evidence for a functional interface between EAATs and glial fibrillary acidic protein (GFAP) relevant to astrocytic morphology led to investigations of actions of transportable (d-Aspartate (d-Asp) and (2S,3S,4R)-2-(carboxycyclopropyl)glycine (l-CCG-III)) and non-transportable (dl-threo-β-benzyloxyaspartate (dl-TBOA)) inhibitors of Glu uptake in murine astrocytes. d-Asp (1 mM), l-CCG-III (0.5 mM) and dl-TBOA (0.5 mM) produced time-dependent (24–72 h) reductions in 3[H]d-Asp uptake (approximately 30–70%) with little or no gliotoxicity. All drugs induced a profound change in phenotype from cobblestone to stellate morphology and image analysis revealed increases in the intensity of GFAP immunolabelling for l-CCG-III and dl-TBOA. Cytochemistry indicated localized changes in F-actin distribution. Cell surface expression of EAAT2, but not EAAT1, was elevated at 72 h. Blockade of Glu uptake by both types of EAAT inhibitor exerts longer-term effects on astrocytic morphology and a compensatory homeostatic rise in EAAT2 abundance.  相似文献   

12.
Basically the peptidoglycan of Myxobater AL-1 consists of alternating β-1,4-linked N-acetylglucosamic-N-acetylmuramic acid chains. After splitting the aminosugar backbone with a specific algal enzyme three subunits arise: a monomer, a dimer and a trimer. Investigation of the monomer with specific enzymes and comparison of the degradation products to standards derived from other bacterial peptidoglycans suggest the following structure of the monomer peptide: l-alanyl-d-glutamic-l-meso-diaminopimelic-d-alanine. A d-alanyl-d-meso-diaminopimelic acid bond is the bridgebond between the peptides of the subunits.  相似文献   

13.
Twelve different amino acids were each substituted for threonine-654 in a cloned glucansucrase from Leuconostoc mesenteroides NRRL B-1118. Both the native and the cloned enzyme with threonine at position 654 produced a water-insoluble glucan containing approximately 44 mol% 1,3-disubstituted α-d-glucopyranosyl units and 29 mol% 1,6-disubstituted α-d-glucopyranosyl units. Several substitutions yielded an enzyme that produced an increased percentage of 1,3-disubstituted α-d-glucopyranosyl units, with corresponding decreases in 1,6-disubstituted α-d-glucopyranosyl units. Only one substitution, tyrosine, resulted in a significant increase in the percentage of 1,6-disubstituted α-d-glucopyranosyl units, with a concomitant increase in glucan yield. The mutated enzymes that produced the highest levels of 1,3-disubstituted α-d-glucopyranosyl units were also significantly activated by the addition of dextran, but glucan yields were also lower in these mutants.  相似文献   

14.
We have proposed a new mannan catabolic pathway in Bacteroides fragilis NCTC 9343 that involves a putative mannanase ManA in glycoside hydrolase family 26 (BF0771), a mannobiose and/or sugar transporter (BF0773), mannobiose 2-epimerase (BF0774), and mannosylglucose phosphorylase (BF0772). If this hypothesis is correct, ManA has to generate mannobiose from mannans as the major end product. In this study, the BF0771 gene from the B. fragilis genome was cloned and expressed in Escherichia coli cells. The expressed protein was found to produce mannobiose exclusively from mannans and initially from manno-oligosaccharides. Production of 4-O-β-d-glucopyranosyl-d-mannose or 4-O-β-d-mannopyranosyl-d-glucose from mannans was not detectable. The results indicate that this enzyme is a novel mannobiose-forming exo-mannanase, consistent with the new microbial mannan catabolic pathway we proposed.  相似文献   

15.
A possible role of arabinogalactan proteins in control of shoot regeneration from stem explants of two citrus cultivars, Carrizo citrange and ‘Duncan’ grapefruit, was investigated. Treatment of explants with (β-d-Glc)3 Yariv phenylglycoside, able to bind specifically to AGPs, led to a decrease of cumulative regeneration potential of both Carrizo citrange and ‘Duncan’ grapefruit. For Carrizo, lower cumulative regeneration potential on (β-d-Glc)3 Yariv phenylglycoside-treated explants was the result of both lower number of shoots on the explants that had shoots (explant regeneration potential) and decreased percentage of explants with shoots. In the case of ‘Duncan’, treatment with (β-d-Glc)3 Yariv phenylglycoside reduced cumulative regeneration potential only by lowering the percentage of explants with shoots, but it did not affect the number of shoots on the explants with shoots. Citrus explants treated with (α-d-Man)3 Yariv phenylglycoside, which does not bind AGPs, responded similarly to untreated explants. Transformability of cells on the cut ends of explants was also lower for both cultivars following the treatment of explants with (β-d-Glc)3 Yariv phenylglycoside. Our data suggest that arabinogalactan proteins play important role in processes controlling differentiation and genetic transformation of citrus cells by Agrobacterium.  相似文献   

16.
Cyclic depsipeptide FK228 with an intramolecular disulfide bond is a potent inhibitor of histone deacetylases (HDAC). FK228 is stable in blood because of its prodrug function, whose –SS– bond is reduced within the cell. Here, cyclic peptides with –SS– bridges between a variety of amino acids were synthesized and assayed for HDAC inhibition. Cyclic peptide 3, cyclo(-l-amino acid-l-amino acid-l-Val-d-Pro-), with an –SS– bridge between the first and second amino acids, was found to be a potent HDAC inhibitor. Cyclic peptide 7, cyclo(-l-amino acid-d-amino acid-l-Val-d-Pro-), with an –SS– bridge between the first and second amino acids, was also a potent HDAC inhibitor.  相似文献   

17.
We investigated d-amino acid oxidase (DAO) induction in the popular model yeast Schizosaccharomyces pombe. The product of the putative DAO gene of the yeast expressed in E.?coli displayed oxidase activity to neutral and basic d-amino acids, but not to an l-amino acid or acidic d-amino acids, showing that the putative DAO gene encodes catalytically active DAO. DAO activity was weakly detected in yeast cells grown on a culture medium without d-amino acid, and was approximately doubled by adding d-alanine. The elimination of ammonium chloride from culture medium induced activity by up to eight-fold. l-Alanine also induced the activity, but only by about half of that induced by d-alanine. The induction by d-alanine reached a maximum level at 2?h cultivation; it remained roughly constant until cell growth reached a stationary phase. The best inducer was d-alanine, followed by d-proline and then d-serine. Not effective were N-carbamoyl-d,l-alanine (a better inducer of DAO than d-alanine in the yeast Trigonopsis variabilis), and both basic and acidic d-amino acids. These results showed that S. pombe DAO could be a suitable model for analyzing the regulation of DAO expression in eukaryotic organisms.  相似文献   

18.
The present study focuses on characterization of two hemicellulases, RuXyn1 and RuXyn2, from rumen bacterial metagenome and their capabilities for degradation of xylans. Glycosyl hydrolase (GH) family?43 ??-d-xylosidase/??-l-arabinofuranosidase RuXyn1 can hydrolyze p-nitrophenyl-??-d-xylopyranoside (pNPX), p-nitrophenyl-??-l-arabinofuranoside (pNPA), and xylo-oligosaccharide substrates, while GH30 1,5-??-l-arabinofuranosidase/??-d-xylosidase RuXyn2, the first ??-l-arabinofuranosidase assigned to this GH family, shows activities towards 1,5-??-l-arabinobiose and pNPX substrates but no activity for pNPA. Kinetic analysis for aryl-glycosides revealed that RuXyn2 had higher catalytic efficiency than RuXyn1 toward pNPX substrate. RuXyn1 shows high synergism with endoxylanase, elevating by 73% the reducing sugars released from brichwood xylans, and converted most intermediate xylo-oligosaccharide hydrolysate into xylose. The high xylose conversion capability of RuXyn1 suggests it has potential applications in enzymatic production of xylose and improvement of hemicellulose saccharification for production of biofuels. RuXyn2 shows no obviously synergistic effect in the endoxylanase-coupled assay for enzymatic saccharification of xylan. Further cosmid DNA sequencing revealed a neighboring putative GH43 ??-l-arabinofuranosidase RuAra1 and two putative GH3 ??-xylosidase/arabinosidases, RuXyn3 and RuXyn5, downstream of RuXyn2, indicating that this hemicellulase gene cluster may be responsible for production of end-product, xylose and arabinose, from hemicellulose biomass.  相似文献   

19.
We performed sensory evaluations on 141 bottles of sake and analyzed the relationship between the d-amino acid concentrations, and the taste of the sake using principal component analysis, which yielded seven principal components (PC1–7) that explained 100 % of the total variance in the data. PC1, which explains 33.6 % of the total variance, correlates most positively with strong taste and most negatively with balanced tastes. PC2, which explains 54.4 % of the total variance, correlates most positively with a sweet taste and most negatively with bitter and sour tastes. Sakes brewed with “Kimoto yeast starter” and “Yamahaimoto” had high scores for PC1 and PC2, and had strong taste in comparison with sakes brewed with “Sokujo-moto”. When present at concentrations below 50 μM, d-Ala did not affect the PC1 score, but all the sakes showed a high PC1 score, when the d-Ala was above 100 μM. Similar observations were found for the d-Asp and d-Glu concentrations with regard to PC1, and the threshold concentrations of d-Asp and d-Glu that affected the taste were 33.8 and 33.3 μM, respectively. Certain bacteria present in sake, especially lactic acid bacteria, produce d-Ala, d-Asp and d-Glu during storage, and these d-amino acids increased the PC1 score and produced a strong taste (Nojun). When d- and l-Ala were added to the sakes, the value for the umami taste in the sensory evaluation increased, with the effect of d-Ala being much stronger than that of l-Ala. The addition of 50–5,000 μM dl-Ala did not effect on the aroma of the sakes at all.  相似文献   

20.
Lactosucrose (O-β-d-galactopyranosyl-(1,4)-O-α-d-glucopyranosyl-(1,2)-β-d-fructofuranoside) is a trisaccharide formed from lactose and sucrose by enzymatic transglycosylation. This rare trisaccharide is a kind of indigestible carbohydrate, has good prebiotic effect, and promotes intestinal mineral absorption. It has been used as a functional ingredient in a range of food products which are approved as foods for specified health uses in Japan. Using lactose and sucrose as substrates, lactosucrose can be produced through transfructosylation by β-fructofuranosidase from Arthrobacter sp. K-1 or a range of levansucrases, or through transgalactosylation by β-galactosidase from Bacillus circulans. This article presented a review of recent studies on the physiological functions of lactosucrose and the biological production from lactose and sucrose by different enzymes.  相似文献   

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