The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Risto Renkonen - One of the best experts on this subject based on the ideXlab platform.

  • REVIEW Biosynthesis of 6-Deoxyhexose glycans in bacteria
    2003
    Co-Authors: Minna Maèki, Risto Renkonen
    Abstract:

    After the breakthroughs in genomic sequencing, one of the next challenges remains to understand the molecular biology of other classes of biomolecules, such as protein and lipids, many of which carry specific glycomodification when mediat-ing their biological functions. This review focuses on the 6-Deoxyhexose biosynthesis of cell surface glycans of three Gram-negative pathogens, Helicobacter pylori, Pseudomonas aeruginosa, and Actinobacillus actinomycetemcomitans sero-type a. 6-Deoxysugars are important functional components of cell surface glycans, and their biosynthetic pathways might be suitable targets for novel interventions of antibacterial chemotherapy. Key words: 6-deoxy-talose/fucose/rhamnose/nucleotide sugar

  • Cloning and functional expression of a novel GDP-6-deoxy-D-talose synthetase from Actinobacillus actinomycetemcomitans
    2002
    Co-Authors: Minna Maki, Jarkko Rabina, Nina Jarvinen, Pirkko Mattila, Risto Renkonen
    Abstract:

    Actinobacillus actinomycetemcomitans is a Gram-negative coccobacillus that can cause various forms of severe periodontitis and other nonoral infections in human patients. The serotype a±specific polysaccharide antigen of A. actinomycetemcomitans contains solely 6-deoxy-D-talose and its O-2 acetylated modification. This polysaccharide is synthesized from the donor GDP-6-deoxy-D-talose with the relevant talosylation enzyme(s). In the synthesis of GDP-6deoxy-D-talose, GDP-D-mannose is first converted by GDP-mannose-4,6-dehydratase (GMD) to GDP-4-keto-6-deoxy-D-mannose and then reduced to GDP-6-deoxy-Dtalose by GDP-6-deoxy-D-talose synthetase (GTS). In this study, we cloned and overexpressed in Escherichia coli the A. actinomycetemcomitans GTS enzyme responsible for the synthesis of GDP-6-deoxy-D-talose. The recombinant A. actinomycetemcomitans GTS enzyme expressed in E. coli converted the GDP-4-keto-6-deoxy-intermediate to a novel GDP-Deoxyhexose. The synthesized GDP-Deoxyhexose was shown to be GDP-6-deoxy-D-talose by HPLC, MALDI-TOF MS, and NMR spectroscopy. The functional expression of gts provides another enzymatically defined pathway for the synthesis of GDP-Deoxyhexoses, which can be used as donors for the corresponding glycosyltransferases

  • analysis of nucleotide sugars from cell lysates by ion pair solid phase extraction and reversed phase high performance liquid chromatography
    Glycoconjugate Journal, 2001
    Co-Authors: Jarkko Rabina, Minna Maki, E Savilahti, Nina Jarvinen, Leena Penttila, Risto Renkonen
    Abstract:

    Analysis of nucleotide sugar metabolism is essential in studying glycosylation in cells. Here we describe practical methods for both extraction of nucleotide sugars from cell lysates and for their analytical separation. Solid-phase extraction cartridges containing graphitized carbon can be used for the purification of nucleotide sugars by using triethylammonium acetate buffer as a ion-pairing reagent for decreasing retention. After that they are separated by high-performance liquid chromatography using a C18 reversed-phase column and the same ion-pairing reagent for increasing retention. These new sample preparation and analysis methods enable good separation of structurally similar sugar nucleotides, compatibility with rapid evaporative concentration, and possibility to automation. Monitoring the production of GDP-Deoxyhexoses in genetically engineered yeast and native bacterial cells are described here as specific applications.

Iain B H Wilson - One of the best experts on this subject based on the ideXlab platform.

  • presence of galactosylated core fucose on n glycans in the planaria dugesia japonica
    Journal of Mass Spectrometry, 2011
    Co-Authors: Katharina Paschinger, Ebrahim Razzazifazeli, Kiyoshi Furukawa, Iain B H Wilson
    Abstract:

    Planarial species are of especial interest to biologists due to the phenomenon of pluripotency and, in comparison to other developmental processes, it can be hypothesised that glycan–lectin interactions may play a role. In order to examine the N-glycans of one of these organisms, Dugesia japonica, peptide:N-glycosidase A was employed and the released glycans were subject to pyridylamination, HPLC and mass spectrometric analysis. A range of oligomannosidic glycans was observed with a trimethylated Man5GlcNAc2 structure being the dominant species. Three glycans were also observed to contain Deoxyhexose; in particular, a glycan with the composition Hex4HexNAc2Fuc1Me2 was revealed by exoglycosidase digestion, in combination with MS/MS, to contain a galactosylated core α1,6-fucose residue, whereas this core modification was found to be capped with a methylhexose residue in the case of a Hex5HexNAc2Fuc1Me3 structure. This is the first report of these types of structures in a platyhelminth and indicates that the ‘GalFuc’ modification of N-glycans is not just restricted to molluscs and nematodes. Copyright © 2011 John Wiley & Sons, Ltd.

Seppo Auriola - One of the best experts on this subject based on the ideXlab platform.

  • high performance liquid chromatography with electrospray ionization mass spectrometry and diode array ultraviolet detection in the identification of flavonol aglycones and glycosides in berries
    Journal of Chromatography A, 1998
    Co-Authors: Sari Hakkinen, Seppo Auriola
    Abstract:

    High-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) was used to study flavonol aglycones and glycosides in berries. For the identification of aglycones, photodiode-array detection (DAD) was also used. The HPLC-ESI-MS technique is highly valuable in the identification of flavonol aglycones and glycosides from berry extracts. This ionization technique provides information on the structure of the aglycones and glycosides without time-consuming pre-purification or derivatization steps. Quercetin aglycone was identified with both ESI-MS and DAD in all of the berries studied. Myricetin aglycone was identified with both techniques in three berries. Hexose, Deoxyhexose-hexose and pentose derivatives of quercetin were the most abundant flavonol glycosides identified. Two glycosides of myricetin and one glycoside of kaempferol were identified in blackcurrant. To confirm the data obtained using the HPLC-ESI-MS procedure, fractions of the glycosides from four berries were separated, hydrolyzed, silylated and the sugars were analyzed using gas chromatography-mass spectrometry.

Katharina Paschinger - One of the best experts on this subject based on the ideXlab platform.

  • presence of galactosylated core fucose on n glycans in the planaria dugesia japonica
    Journal of Mass Spectrometry, 2011
    Co-Authors: Katharina Paschinger, Ebrahim Razzazifazeli, Kiyoshi Furukawa, Iain B H Wilson
    Abstract:

    Planarial species are of especial interest to biologists due to the phenomenon of pluripotency and, in comparison to other developmental processes, it can be hypothesised that glycan–lectin interactions may play a role. In order to examine the N-glycans of one of these organisms, Dugesia japonica, peptide:N-glycosidase A was employed and the released glycans were subject to pyridylamination, HPLC and mass spectrometric analysis. A range of oligomannosidic glycans was observed with a trimethylated Man5GlcNAc2 structure being the dominant species. Three glycans were also observed to contain Deoxyhexose; in particular, a glycan with the composition Hex4HexNAc2Fuc1Me2 was revealed by exoglycosidase digestion, in combination with MS/MS, to contain a galactosylated core α1,6-fucose residue, whereas this core modification was found to be capped with a methylhexose residue in the case of a Hex5HexNAc2Fuc1Me3 structure. This is the first report of these types of structures in a platyhelminth and indicates that the ‘GalFuc’ modification of N-glycans is not just restricted to molluscs and nematodes. Copyright © 2011 John Wiley & Sons, Ltd.

  • Presence of galactosylated core fucose on N-glycans in the planaria Dugesia japonica
    2011
    Co-Authors: Katharina Paschinger, Ebrahim A Razzazi-fazeli, Kiyoshi Furukawa B C, Iain Wilson B. H. A
    Abstract:

    Planarial species are of especial interest to biologists due to the phenomenon of pluripotency and, in comparison to other developmental processes, it can be hypothesised that glycan–lectin interactions may play a role. In order to examine the N-glycans of one of these organisms, Dugesia japonica, peptide: N-glycosidase A was employed and the released glycans were subject to pyridylamination, HPLC and mass spectrometric analysis. A range of oligomannosidic glycans was observed with a trimethylated Man5GlcNAc2 structure being the dominant species. Three glycans were also observed to contain Deoxyhexose; in particular, a glycan with the composition Hex4HexNAc2Fuc1Me2 was revealed by exoglycosidase digestion, in combination with MS/MS, to contain a galactosylated core α1,6-fucose residue, whereas this core modification was found to be capped with a methylhexose residue in the case of a Hex5HexNAc2Fuc1Me3 structure. This is the first report of these types of structures in a platyhelminth and indicates that the ‘GalFuc ’ modification of N-glycans is not just restricted to molluscs and nematodes. Copyright c ○ 2011 John Wiley & Sons, Ltd. Supporting information may be found in the online version of this article. Keywords: Galβ1,4Fuc epitope; planaria; N-glycan; methylhexose; mass spectrometr

Angel Gilizquierdo - One of the best experts on this subject based on the ideXlab platform.

  • new c deoxyhexosyl flavones and antioxidant properties of passiflora edulis leaf extract
    Journal of Agricultural and Food Chemistry, 2007
    Co-Authors: Federico Ferreres, Carla Sousa, Patricia Valentao, Paula B Andrade, Rosa M Seabra, Angel Gilizquierdo
    Abstract:

    The flavonoids present in passion fruit (Passiflora edulis) leaves were identified by a high-performance liquid chromatography-diode array detection-tandem mass spectrometry (HPLC-DAD-MS/MS) method. Sixteen apigenin or luteolin derivatives were characterized, which included four mono-C-glycosyl, eight O-glycosyl- C-glycosyl, and four O-glycosyl derivatives. With the exceptions of C-hexosyl luteolin and C-hexosyl apigenin, all the compounds exhibited a Deoxyhexose moiety. Moreover, the uncommon C-deoxyhexosyl derivatives of luteolin and apigenin have been identified for first time in P. edulis by HPLC-DAD-MS/MS. The antioxidative capacity of passion fruit leaves was checked against DPPH radical and several reactive oxygen species (superoxide radical, hydroxyl radical, and hypochlorous acid), revealing it to be concentration-dependent, although a pro-oxidant effect was noticed for hydroxyl radical.