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1.
Lorenzo Romero-Ram��rez Isabel Garc��a-��lvarez Ram��n Campos-Olivas Michel Gilbert Marie-France Goneau Alfonso Fern��ndez-Mayoralas Manuel Nieto-Sampedro 《PloS one》2012,7(12)
Gangliosides are sialic acid containing glycosphingolipids, commonly found on the outer leaflet of the plasma membrane. O-acetylation of sialic acid hydroxyl groups is one of the most common modifications in gangliosides. Studies on the biological activity of O-acetylated gangliosides have been limited by their scarcity in nature. This comparatively small change in ganglioside structure causes major changes in their physiological properties. When the ganglioside GD1b was O-acetylated in the outer sialic acid, it became the potent inhibitor of astroblast and astrocytoma proliferation called Neurostatin. Although various chemical and enzymatic methods to O-acetylate commercial gangliosides have been described, O-acetylation was nonspecific and produced many side-products that reduced the yield. An enzyme with O-acetyltransferase activity (SOAT) has been previously cloned from the bacteria Campylobacter jejuni. This enzyme catalyzed the acetylation of oligosaccharide-bound sialic acid, with high specificity for terminal alpha-2,8-linked residues. Using this enzyme and commercial gangliosides as starting material, we have specifically O-acetylated the gangliosides’ outer sialic acids, to produce the corresponding gangliosides specifically O-acetylated in the sialic acid bound in alpha-2,3 and alpha-2,8 residues. We demonstrate here that O-acetylation occurred specifically in the C-9 position of the sialic acid. In summary, we present a new method of specific O-acetylation of ganglioside sialic acids that permits the large scale preparation of these modified glycosphingolipids, facilitating both, the study of their mechanism of antitumoral action and their use as therapeutic drugs for treating glioblastoma multiform (GBM) patients. 相似文献
2.
《Bioorganic & medicinal chemistry letters》2019,29(18):2609-2612
To identify sialic acid binding proteins from complex proteomes, three photocrosslinking affinity-based probes were constructed using Neu5Ac (5 and 6) and Neu5Ac2en (7) scaffolds. Kinetic inhibition assays and Western blotting revealed the Neu5Ac2en-based 7 to be an effective probe for the labeling of a purified gut microbial sialidase (BDI_2946) and a purified human sialic acid binding protein (hCD33). Additionally, LC–MS/MS affinity-based protein profiling verified the ability of 7 to enrich a low-abundance sialic acid binding protein (complement factor H) from human serum thus validating the utility of this probe in a complex context. 相似文献
3.
Walter A. Szarek G.Wayne Schnarr Harold C. Jarrell J.K.N. Jones 《Carbohydrate research》1977,53(1):101-108
A synthesis of l-dendroketose (5) has been achieved by microbiological oxidation by Acetobacter suboxydans of the branched-chain alditol 2-C-(hydroxymethyl)-d-erythro-pentitol (4). Treatment of the oxidation product with acetone, copper(II) sulfate, and sulfuric acid afforded the two di-O-isopropylidene-l-dendroketose derivatives 6 and 7. Assignment of configuration at the branching carbon atom (C-4) and at the anomeric center in 6 and 7 was made on the basis of the carbon-13 magnetic resonance spectra of these derivatives. 相似文献
4.
Accessibility of sialo components in a murine tumor cell to extracellular glycohydrolase (sialidase)
Lipid-bound sialic acid in the murine melanoma cell is not totally inaccessible to an exogenous macromolecular probe, as formerly believed. Roughly 30% of the sialic acid bound to lipid, and an equal proportion of the sialic acid bound to protein is cleaved by the action of Clostridium perfringens glycohydrolase (neuraminidase, sialidase) when the purified enzyme is added to the suspension medium of intact murine melanoma cells freshly derived from the tumor. Cleavage of lipid-bound sialic acid is indifferent to the presence of Ca2+ in the medium. However, maximum release from protein requires a physiological concentration of this divalent cation. Variation in ionic strength has no effect on release of sialic acid. These findings show that a restricted portion of the bound sialic acid may be released from the intact murine melanama cell by the extracellularly supplied enzyme acting topographically. 相似文献
5.
《Bioorganic & medicinal chemistry》2014,22(15):3994-4000
Tyrosinase is involved in the synthesis of melanin in the skin and hair as well as neuromelanin in the brain. This rate limiting enzyme catalyzes two critical steps (reactions) in melanogenesis; the hydroxylation of tyrosine to form DOPA and the subsequent oxidation of DOPA into dopaquinone. Several new aminophenol derivatives have been synthesized based on structure–activity relationship studies of N-(4-hydroxyphenyl)retinamide (1), a derivative of retinoic acid. In order to find new tyrosinase inhibitors, we investigated the effects of these p-aminophenols, including p-decylaminophenol (3), on the activity of mushroom tyrosinase. Compound 3 was the most potent agent, showing significant inhibition as compared with control. The inhibitory effects of 3 on tyrosinase activities were greater than seen with kojic acid, a well-known potent inhibitor of tyrosinase activity, which also causes adverse effects, including rash and dermatitis. A Lineweaver–Burk kinetic analysis of inhibition showed that 3 suppresses tyrosinase activity in a non-competitive fashion for both substrates, tyrosine and DOPA. These results suggest that 3 might be a useful alternative to kojic acid as a tyrosinase inhibitor. 相似文献
6.
Vigorous trimethylsilylation of dihydropyrimidine and dihydro-s-triazine bases and nucleosides results in their dehydrogenation to the analogous aromatic derivatives. This transformation, which cannot be effected by conventional dehydrogenating reagents, has been studied in detail using gas chromatographic and mass spectrometric methods. For 5,6-dihydro-5-azacytidine (2a) the oxidation is quantitative, requires molecular oxygen as well as reagents capable of both N- and O-silylation, is accelerated by heat and selected free radiacal initiators, and is inhibited by diethyldithiocarbamate and galvinoxyl free radical. This anomalous silylation reaction occurs on both an analytical and preparative scale. Silylation-mediated oxidation also exhibits a substantial deuterium isotope effect with preferential retention of deuterium at the new site of unsaturation. The potential of this new reaction for the synthesis of aromatic systems and for the insertion of non-exchangeable isotopic labels in suitable reduced precursors is illustrated. 相似文献
7.
Ashok K. Shukla Norbert Scholz Ernst H. Reimerdes Roland Schauer 《Analytical biochemistry》1982,123(1):78-82
A rapid, isocratic high-performance liquid chromatographic method for the analysis of N-acetylneuraminic acid, N-glycolylneuraminic acid, and their O-acetylated derivatives is described. Separation of sialic acids and of other monosaccharides as sugar-borate complexes is achieved on an anion-exchange resin. The sialic acids elute as individual peaks after the other sugars tested. The method allows quantitative determination, for example, of amounts of N-acetylneuraminic acid as small as 10 nmol. On cation-exchange resin sialic acids cannot be differentiated, but can be separated from neutral and amino sugars, allowing the determination of as little as 3 nmol of total sialic acids. 相似文献
8.
《Biochimica et Biophysica Acta (BBA)/General Subjects》2019,1863(10):1471-1479
BackgroundSialylation of glycoproteins and glycolipids is important for biological processes such as cellular communication, cell migration and protein function. Biosynthesis of CMP-sialic acid, the essential substrate, comprises five enzymatic steps, involving ManNAc and sialic acid and their phosphorylated forms as intermediates. Genetic diseases in this pathway result in different and tissue-restricted phenotypes, which is poorly understood.Methods and resultsWe aimed to study the mechanisms of sialic acid metabolism in knockouts (KO) of the sialic acid pathway in two independent cell lines. Sialylation of cell surface glycans was reduced by KO of GNE (UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase), NANS (sialic acid synthase) and CMAS (N-acylneuraminate cytidylyltransferase) genes, but was largely unaffected in NANP (N-acylneuraminate-9-phosphatase) KO, as studied by MAA and PNA lectin binding. NANP is the third enzyme in sialic acid biosynthesis and dephosphorylates sialic acid 9-phosphate to free sialic acid. LC-MS analysis of sialic acid metabolites showed that CMP-sialic acid was dramatically reduced in GNE and NANS KO cells and undetectable in CMAS KO. In agreement with normal cell surface sialylation, CMP-sialic acid levels in NANP KO were comparable to WT cells, even though sialic acid 9-phosphate, the substrate of NANP accumulated. Metabolic flux analysis with 13C6-labelled ManNAc showed a lower, but significant conversion of ManNAc into sialic acid.ConclusionsOur data provide evidence that NANP activity is not essential for de novo sialic acid production and point towards an alternative phosphatase activity, bypassing NANP.General significanceThis report contributes to a better understanding of sialic acid biosynthesis in humans. 相似文献
9.
Boris-Marko Kukovec Šebojka Komorsky-Lovri? Marijana Vinkovi? 《Inorganica chimica acta》2009,362(8):2704-1896
Cobalt complexes of 3- and 6-methylpicolinic acid, namely [Co(3-Mepic)3] (1) and [Co(6-Mepic)2(H2O)2] · 2H2O (2) were prepared and characterized by spectroscopic methods (IR, UV-Vis, NMR), their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA/DTA methods. Square-wave voltammetry showed that on mercury electrode the oxidation of 2 requires higher potential than the oxidation of complex anion [Co(3-Mepic)3]−, the most probable product of the reduction of 1. The reduction of 1 and the oxidation of 2 depend on the kinetics of electron transfer and the electrode material. X-ray structural analysis revealed octahedral coordination polyhedron in both 1 and 2 and the same N,O-chelated coordination mode for both ligands. 13C, 1H and 15N NMR spectroscopy confirmed that coordination mode of 3-methylpicolinic acid in 1 in DMSO solution. UV-Vis spectrophotometric measurements were used to study the complexation of cobalt with 3- and 6-methylpicolinic acid in aqueous solution and to determine the composition of the formed complexes by Job method of continuous variation. The stoichiometry of the complex with 3-methylpicolinic acid is 2:3, while it is 2:3 and 3:2 for the complex with 6-methylpicolinic acid, indicating the possibility of the formation of more than one complex species. 相似文献
10.
Plasmodium berghei: modification of sialic acid on red cells from infected mouse blood 总被引:1,自引:0,他引:1
The surface membrane glycoproteins of normal mouse erythrocytes can be labeled by oxidation with either periodate or galactose oxidase in the presence of neuraminidase, followed by reduction with NaB3H4. Without neuraminidase there is little galactose oxidase-catalyzed labeling of protein. Analysis of labeled proteins by SDS-polyacrylamide gel electrophoresis showed that both methods labeled the same set of glycoproteins. Plasmodium berghei infection dramatically reduced the sialoglycoprotein labeling of red blood cells from infected blood using the periodate/NaB3H4 method. Provided neuraminidase was present, labeling by the galactose oxidase method gave identical results to normal erythrocytes. We conclude that the glycoprotein sialic acid of uninfected as well as infected red cells is modified during infection such that it is refractory to periodate oxidation. Acylation of the exocyclic hydroxyls of sialic acid is suggested to account for this. Lectin binding and cell agglutination experiments using Limulin, soybean and wheatgerm lectins, and concanavalin A confirmed and extended these observations. The possible implications of these results with regard to anemia induced by malaria are briefly discussed. 相似文献
11.
《Bioorganic & medicinal chemistry letters》2020,30(17):127407
In this study, seven 30-norlupane derivatives (2–8) was obtained from the chemical oxidation of betulinic acid followed by biotransformation via Bacillus megaterium CGMCC 1.1741. And metabolites 2–4 and 6–8 were newly identified products. In the first step, betulinic acid was chemically oxidized to platanic acid (1). Following the chemical oxidation, B. megaterium catalyzed the hydroxylation at C-7, C-11, C-15 and C-23 of platanic acid (1) as well as the oxidation of C-3 hydroxyl group. Compared to the labor-intensive isolation from natural plants, this chemical-microbial semi-synthesis is more capable to provide increased structural diversity of oxygenated 30-norlupane. Finally, the potential neuroprotective effect of the derivatives was assessed on neuron-like PC12 cells induced by cobalt chloride (CoCl2). Metabolite 6 showed a potent neuroprotective activity. 相似文献
12.
The following cyclic compounds were oxidized at 4° by means of aqueous sodium peroxide in large excess: 2,3,4,6/5-pentahydroxycyclohexanone (1); xylo-pentahydroxy-2-cyclohexen-l-one (2); xylo-trihydroxycyclohexane-1,2,3-trione (3); reductic acid (4); and ninhydrin (5). On oxidation, 1, 2, and 3 gave carbon dioxide, formic acid, and oxalic acid; in addition, 1 yielded DL-glucaric acid, and 2 and 3 afforded xylaric acid. Compound 4 gave almost equimolecular quantities of carbon dioxide and succinic acid. In addition to a small amount of formic acid, compound 5 gave carbon dioxide and phthalic acid in yields of 92 and 95%, respectively. Reaction mechanisms are proposed. 相似文献
13.
Hye-Kyeong Kim Min-Kyong Kwon Jin-Nam Kim Chang-Kwon Kim Yeon-Ju Lee Hee Jae Shin Joongku Lee Hyi-Seung Lee 《Phytochemistry letters》2010,3(4):238-241
Two new fatty acid glucosides, 1,6-di-O-octanoyl-β-D-glucopyranose (1) and 6-O-(β-D-glucopyranosyl)-1-O-decanoyl-β-D-glucopyranose (2), were isolated from a methanol extract of the fruit of Morinda citrifolia L. along with five known saccharide fatty acid esters. The structures of these compounds were determined by combination of spectral and chemical analyses. These fatty acid glucosides exhibited inhibitory effect against copper-induced low-density lipoprotein oxidation. Compound 2 had the strongest effect, which was almost comparable to that of butylated hydroxytoluene. 相似文献
14.
The mechanism of formation of [FeIV(O)(N4Py)]2+ (2, N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) from the reaction of [FeII(N4Py)(CH3CN)]2+ (1) with m-chloroperbenzoic acid (mCPBA) in CH2Cl2 at −30 °C has been studied on the basis of the visible spectral changes observed and the reaction stoichiometry. It is shown that the conversion of 1 to 2 in 90% yield requires 1.5 equiv. peracid and takes place in two successive one-electron steps via an [FeIII(N4Py)OH]2+(3) intermediate. The first oxidation step uses 0.5 equiv. peracid and produces 0.5 equiv. 3-chlorobenzoic acid, while the second step uses 1 equiv. peracid and affords byproducts derived from chlorophenyl radical. We conclude that the FeII(N4Py) center promotes O-O bond heterolysis, while the FeIII(N4Py) center favors O-O bond homolysis, so the nature of O-O bond cleavage is dependent on the iron oxidation state. 相似文献
15.
Treatment of methyl β-d-ribofuranoside with acetone gave methyl 2,3-O-isopropylidene-β-d-ribofuranoside (1, 90%), whereas methyl α-d-ribofuranoside gave a mixture (30%) of 1 and methyl 2,3-O-isopropylidene-α-d-ribofuranoside (1a). On oxidation, 1 gave methyl 2,3-O-isopropylidene-β-d-ribo-pentodialdo-1,4-furanoside (2), whereas no similar product was obtained on oxidation of 1a. Ethynylmagnesium bromide reacted with 2 in dry tetrahydrofuran to give a 1:1 mixture (95%) of methyl 6,7-dideoxy-2,3-O-isopropylidene-β-d-allo- (3) and -α-l-talo-hept-6-ynofuranoside (4). Ozonolysis of 3 and 4 in dichloromethane gave the corresponding d-allo- and l-talo-uronic acids, characterized as their methyl esters (5 and 6) and 5-O-formyl methyl esters (5a and 6a). Ozonolysis in methanol gave a mixture of the free uronic acid and the methyl ester, and only a small proportion of the 5-O-formyl methyl ester. Malonic acid reacted with 2 to give methyl 5,6-dideoxy-2,3-O-isopropylidene-β-d-ribo-trans-hept-5-enofuranosiduronic acid (7). 相似文献
16.
Juji Yoshimura Masafumi Matsuzawa Ken-ichi Sato Yuli Nagasawa 《Carbohydrate research》1979,76(1):67-78
Evernitrose (2,3,6-trideoxy-3-C-methyl-4-O-methyl-3-nitro-L-arabino-hexopyranose) was synthesized from methyl 2,6-dideoxy-4-O-methyl-α-L-erythro-hexopyranosid-3-ulose (2) through introduction of an amino group attached to the tertiary branching carbon by the method of Bourgeois, and subsequent oxidation of the amino group by m-chloroperoxybenzoic acid to a nitro group. 3-Cyano-3-O-mesylation of 2 by Bourgeois's method gave exclusively the desired product having the L-ribo configuration; furthermore, the β anomer of 2 gave the L-ribo and L-arabino products in the ratio of 1:2. The latter compound was converted into 3-epi-evernitrose by a similar sequence of reactions. 相似文献
17.
N-Propanoylmannosamine is an unnatural precursor of sialic acid, which is taken up by a variety of animal cells and metabolized to N-propanoylneuraminic acid. In several studies it has been demonstrated that application of unnatural precursors of sialic acids such as N-propanoylmannosamine (ManNProp) and homologues interfere with cell differentiation and proliferation of neuronal cells or embryonic stem cells. Since the function of the immune system is known to rely on the presence of sialic acid, we applied ManNProp to human peripheral blood mononuclear cells (PBMC). When culturing those lymphocytes with ManNProp 10 % of the natural sialic acid N-acetylneuraminic acid could be replaced by the newly formed N-propanoylneuraminic acid. This procedure resulted (a) in a marked stimulation in the rate of proliferation of PBMC, (b) a 10-fold increase of IL-2 production coupled with an up-regulation of its receptor CD25 on the cell surface and (c) a concomitant expression and regulation of the transferrin receptor with cell growth. The stimulation of PBMC by ManNProp might therefore introduce a new approach of immunomodulation. 相似文献
18.
Mark T. Anderson Stephanie D. Himpsl Lindsay A. Mitchell Leandra G. Kingsley Elizabeth P. Snider Harry L. T. Mobley 《PLoS pathogens》2022,18(3)
Serratia marcescens is a versatile opportunistic pathogen that can cause a variety of infections, including bacteremia. Our previous work established that the capsule polysaccharide (CPS) biosynthesis and translocation locus contributes to the survival of S. marcescens in a murine model of bacteremia and in human serum. In this study, we determined the degree of capsule genetic diversity among S. marcescens isolates. Capsule loci (KL) were extracted from >300 S. marcescens genome sequences and compared. A phylogenetic comparison of KL sequences demonstrated a substantial level of KL diversity within S. marcescens as a species and a strong delineation between KL sequences originating from infection isolates versus environmental isolates. Strains from five of the identified KL types were selected for further study and electrophoretic analysis of purified CPS indicated the production of distinct glycans. Polysaccharide composition analysis confirmed this observation and identified the constituent monosaccharides for each strain. Two predominant infection-associated clades, designated KL1 and KL2, emerged from the capsule phylogeny. Bacteremia strains from KL1 and KL2 were determined to produce ketodeoxynonulonic acid and N-acetylneuraminic acid, two sialic acids that were not found in strains from other clades. Further investigation of KL1 and KL2 sequences identified two genes, designated neuA and neuB, that were hypothesized to encode sialic acid biosynthesis functions. Disruption of neuB in a KL1 isolate resulted in the loss of sialic acid and CPS production. The absence of sialic acid and CPS production also led to increased susceptibility to internalization by a human monocytic cell line, demonstrating that S. marcescens phagocytosis resistance requires CPS. Together, these results establish the capsule genetic repertoire of S. marcescens and identify infection-associated clades with sialic acid CPS components. 相似文献
19.
The baculovirus/insect cell system is widely used for recombinant protein production, but it is suboptimal for recombinant glycoprotein production because it does not provide sialylation, which is an essential feature of many glycoprotein biologics. This problem has been addressed by metabolic engineering, which has extended endogenous insect cell N-glycosylation pathways and enabled glycoprotein sialylation by baculovirus/insect cell systems. However, further improvement is needed because even the most extensively engineered baculovirus/insect cell systems require media supplementation with N-acetylmannosamine, an expensive sialic acid precursor, for efficient recombinant glycoprotein sialylation. Our solution to this problem focused on E. coli N-acetylglucosamine-6-phosphate 2′-epimerase (GNPE), which normally functions in bacterial sialic acid degradation. Considering that insect cells have the product, but not the substrate for this enzyme, we hypothesized that GNPE might drive the reverse reaction in these cells, thereby initiating sialic acid biosynthesis in the absence of media supplementation. We tested this hypothesis by isolating transgenic insect cells expressing E. coli GNPE together with a suite of mammalian genes needed for N-glycoprotein sialylation. Various assays showed that these cells efficiently produced sialic acid, CMP-sialic acid, and sialylated recombinant N-glycoproteins even in growth media without N-acetylmannosamine. Thus, this study demonstrated that a eukaryotic recombinant protein production platform can be glycoengineered with a bacterial gene, that a bacterial enzyme which normally functions in sialic acid degradation can be used to initiate sialic acid biosynthesis, and that insect cells expressing this enzyme can produce sialylated N-glycoproteins without N-acetylmannosamine supplementation, which will reduce production costs in glycoengineered baculovirus/insect cell systems. 相似文献
20.
Rajendra M. Srivastava Norman Hudson Fred R. Seymour Bernard Weissmann 《Carbohydrate research》1978,60(2):315-326
The earlier preparation of cyclohexylammonium (phenyl α-l-idopyranosid)-uronate has been improved, and (4-methylumbelliferyl α-l-idopyranosid)uronic acid (14), a more sensitive substrate for α-l-iduronidase, has been synthesized by an analogous route. Zinc chloride-catalyzed condensation of 4-methylumbelliferone with 1,2,3,4,6-penta-O-acetyl-α-l-idopyranose (4) in 1,2-ethanediol diacetate gave crystalline 4-methylumbelliferyl 2,3,4,6-tetra-O-acetyl-α-l-idopyranoside (7). O-Deacetylation and catalytic oxidation gave 14, characterized as a cyclohexylammonium salt. The starting material 4 was prepared, in 21 % yield from l-glucose, by conversion of the intermediate 1,2,3,4,6-penta-O-acetyl-β-l-glucopyranose to 2,3,4,6-tetra-O-acetyl-β-l-glucopyranosyl chloride and acetoxonium ion rearrangement, as described for the D-series. 相似文献