Aldonolactone - Explore the Science & Experts | ideXlab



Scan Science and Technology

Contact Leading Edge Experts & Companies

Aldonolactone

The Experts below are selected from a list of 405 Experts worldwide ranked by ideXlab platform

Aldonolactone – Free Register to Access Experts & Abstracts

Rosa M. De Lederkremer – One of the best experts on this subject based on the ideXlab platform.

  • Synthesis of arabinofuranose branched galactofuran tetrasaccharides, constituents of mycobacterial arabinogalactan†
    Organic & biomolecular chemistry, 2011
    Co-Authors: Lucía Gandolfi-donadío, Rosa M. De Lederkremer, Malena Santos, Carola Gallo-rodriguez

    Abstract:

    Mycolyl-arabinogalactan (mAG) complex is a major component of the cell wall of Mycobacterium tuberculosis, the causative agent of tuberculosis disease. Due to the essentiality of the cell wall for mycobacterium viability, knowledge of the biosynthesis of the arabinogalactan is crucial for the development of new therapeutic agents. In this context, we have synthesized two new branched arabinogalactafuranose tetrasaccharides, decenyl β-D-Galf-(1→5)-β-D-Galf-(1→6)[α-D-Araf(1→5)]-β-D-Galf (1) and decenyl β-D-Galf-(1→6)-[α-D-Araf-(1→5)]-β-D-Galf-(1→5)-β-D-Galf (2), as interesting tools for arabinofuranosyl transferase studies. The Aldonolactone strategy for the introduction of the internal D-Galf was employed, allowing the construction of oligosaccharides from the non-reducing to the reducing end. Moreover, a one-pot procedure was developed for the synthesis of trisaccharide lactone 21, precursor of 2, which involved a glycosylation-deprotection-glycosylation sequence, through the use of TMSOTf as catalyst of the trichloroacetimidate method as well as promoter of TBDMS deprotection.

    Free Register to Access Article

  • Synthesis of trisaccharides containing internal galactofuranose O-linked in Trypanosoma cruzi mucins
    Carbohydrate research, 2009
    Co-Authors: Verónica M. Mendoza, Rosa M. De Lederkremer, Gustavo A. Kashiwagi, Carola Gallo-rodriguez

    Abstract:

    Abstract The trisaccharides β- d -Gal f -(1→2)-β- d -Gal f -(1→4)- d -GlcNAc ( 5 ) and β- d -Gal p -(1→2)-β- d -Gal f -(1→4)- d -GlcNAc ( 6 ) constitute novel structures isolated as alditols when released by reductive β-elimination from mucins of Trypanosoma cruzi (Tulahuen strain). Trisaccharides 5 and 6 were synthesized employing the Aldonolactone approach. Thus, a convenient d -galactono-1,4-lactone derivative was used for the introduction of the internal galactofuranose and the trichloroacetimidate method was employed for glycosylation reactions. Due to the lack of anchimeric assistance on O-2 of the galactofuranosyl precursor, glycosylation studies were performed under different conditions. The nature of the solvent strongly determined the stereochemical course of the glycosylation reactions when the galactofuranosyl donor was substituted either by 2- O -Gal p or 2- O -Gal f .

    Free Register to Access Article

  • Photoinduced electron-transfer α-deoxygenation of Aldonolactones. Efficient synthesis of 2-deoxy-d-arabino-hexono-1,4-lactone
    Carbohydrate research, 2006
    Co-Authors: Andrea Bordoni, Rosa M. De Lederkremer, Carla Marino

    Abstract:

    Abstract A photoinduced electron-transfer (PET) reaction was used for the deoxygenation at C-2 of Aldonolactones derivatized as 2- O -[3-(trifluoromethyl)benzoyl] or benzoyl esters. By irradiation of different d -galactono- and d -glucono-1,4-derivatives, with a 450 W lamp, using 9-methylcarbazole as photosensitizer, the corresponding 2-deoxy- d – lyxo – and 2-deoxy- d – arabino -hexono-1,4-lactones were efficiently obtained.

    Free Register to Access Article

Nicole G. H. Leferink – One of the best experts on this subject based on the ideXlab platform.

  • Identification of a Gatekeeper Residue That Prevents *□S
    , 2013
    Co-Authors: Dehydrogenases From Acting As Oxidases, Nicole G. H. Leferink, Marco W. Fraaije, Henk-jan Joosten, Peter J. Schaap, Andrea Mattevi, Willem J. H. Van Berkel

    Abstract:

    The oxygen reactivity of flavoproteins is poorly understood. Here we show that a single Ala to Gly substitution in L-galactono-�-lactone dehydrogenase (GALDH) turns the enzyme into a catalytically competent oxidase. GALDH is an Aldonolactone oxidoreductase with a vanillyl-alcohol oxidase (VAO) fold. We found that nearly all oxidases in the VAO family contain either a Gly or a Pro at a structurally conserved position near the C4a locus of the isoalloxazine moiety of the flavin, whereas dehydrogenases prefer another residue at this position. Mutation of the corresponding residue in GALDH (Ala-113 3 Gly) resulted in a striking 400-fold increase in oxygen reactivity, whereas the cytochrome c reductase activity is retained. The activity of the A113G variant shows a linear dependence on oxygen concentration (k ox � 3.5 � 10 5 M �1 s �1), similar to most other flavoprotein oxidases. The Ala-113 3 Gly replacement does not chang

    Free Register to Access Article

  • Galactonolactone oxidoreductase from Trypanosoma cruzi employs a FAD cofactor for the synthesis of vitamin C.
    Biochimica et biophysica acta, 2011
    Co-Authors: Elena V. Kudryashova, Nicole G. H. Leferink, Ilse G.m. Slot, Willem J. H. Van Berkel

    Abstract:

    Trypanosoma cruzi, the aetiological agent of Chagas’ disease, is unable to salvage vitamin C (l-ascorbate) from its environment and relies on de novo synthesis for its survival. Because humans lack the capacity to synthesize ascorbate, the trypanosomal enzymes involved in ascorbate biosynthesis are interesting targets for drug therapy. The terminal step in ascorbate biosynthesis is catalyzed by flavin-dependent Aldonolactone oxidoreductases belonging to the vanillyl-alcohol oxidase (VAO) protein family. Here we studied the properties of recombinant T. cruzi galactonolactone oxidoreductase (TcGAL), refolded from inclusion bodies using a reverse micelles system. The refolded enzyme shows native-like secondary structure and is active with both l-galactono-1,4-lactone and d-arabinono-1,4-lactone. At odd with an earlier claim, TcGAL employs a non-covalently bound FAD as redox-active cofactor. Moreover, it is shown for the first time that TcGAL can use molecular oxygen as electron acceptor. This is in line with the absence of a recently identified gatekeeper residue that prevents Aldonolactone oxidoreductases from plants to act as oxidases.

    Free Register to Access Article

  • Functional assignment of Glu386 and Arg388 in the active site of L-galactono-γ-lactone dehydrogenase.
    FEBS letters, 2009
    Co-Authors: Nicole G. H. Leferink, Mac Donald F. Jose, Willy A. M. Van Den Berg, Willem J. H. Van Berkel

    Abstract:

    Abstract The flavoenzyme l -galactono-γ-lactone dehydrogenase (GALDH) catalyzes the terminal step of vitamin C biosynthesis in plants. Little is known about the catalytic mechanism of GALDH and related Aldonolactone oxidoreductases. Here we identified an essential Glu–Arg pair in the active site of GALDH from Arabidopsis thaliana . Glu386 and Arg388 variants show high K m values for l -galactono-1,4-lactone and low turnover rates. Arg388 is crucial for the stabilization of the anionic form of the reduced FAD cofactor. Glu386 is involved in productive substrate binding. The E386D variant has lost its specificity for l -galactono-1,4-lactone and shows the highest catalytic efficiency with l -gulono-1,4-lactone.

    Free Register to Access Article

Willem J. H. Van Berkel – One of the best experts on this subject based on the ideXlab platform.

  • Identification of a Gatekeeper Residue That Prevents *□S
    , 2013
    Co-Authors: Dehydrogenases From Acting As Oxidases, Nicole G. H. Leferink, Marco W. Fraaije, Henk-jan Joosten, Peter J. Schaap, Andrea Mattevi, Willem J. H. Van Berkel

    Abstract:

    The oxygen reactivity of flavoproteins is poorly understood. Here we show that a single Ala to Gly substitution in L-galactono-�-lactone dehydrogenase (GALDH) turns the enzyme into a catalytically competent oxidase. GALDH is an Aldonolactone oxidoreductase with a vanillyl-alcohol oxidase (VAO) fold. We found that nearly all oxidases in the VAO family contain either a Gly or a Pro at a structurally conserved position near the C4a locus of the isoalloxazine moiety of the flavin, whereas dehydrogenases prefer another residue at this position. Mutation of the corresponding residue in GALDH (Ala-113 3 Gly) resulted in a striking 400-fold increase in oxygen reactivity, whereas the cytochrome c reductase activity is retained. The activity of the A113G variant shows a linear dependence on oxygen concentration (k ox � 3.5 � 10 5 M �1 s �1), similar to most other flavoprotein oxidases. The Ala-113 3 Gly replacement does not chang

    Free Register to Access Article

  • Galactonolactone oxidoreductase from Trypanosoma cruzi employs a FAD cofactor for the synthesis of vitamin C.
    Biochimica et biophysica acta, 2011
    Co-Authors: Elena V. Kudryashova, Nicole G. H. Leferink, Ilse G.m. Slot, Willem J. H. Van Berkel

    Abstract:

    Trypanosoma cruzi, the aetiological agent of Chagas’ disease, is unable to salvage vitamin C (l-ascorbate) from its environment and relies on de novo synthesis for its survival. Because humans lack the capacity to synthesize ascorbate, the trypanosomal enzymes involved in ascorbate biosynthesis are interesting targets for drug therapy. The terminal step in ascorbate biosynthesis is catalyzed by flavin-dependent Aldonolactone oxidoreductases belonging to the vanillyl-alcohol oxidase (VAO) protein family. Here we studied the properties of recombinant T. cruzi galactonolactone oxidoreductase (TcGAL), refolded from inclusion bodies using a reverse micelles system. The refolded enzyme shows native-like secondary structure and is active with both l-galactono-1,4-lactone and d-arabinono-1,4-lactone. At odd with an earlier claim, TcGAL employs a non-covalently bound FAD as redox-active cofactor. Moreover, it is shown for the first time that TcGAL can use molecular oxygen as electron acceptor. This is in line with the absence of a recently identified gatekeeper residue that prevents Aldonolactone oxidoreductases from plants to act as oxidases.

    Free Register to Access Article

  • Functional assignment of Glu386 and Arg388 in the active site of L-galactono-γ-lactone dehydrogenase.
    FEBS letters, 2009
    Co-Authors: Nicole G. H. Leferink, Mac Donald F. Jose, Willy A. M. Van Den Berg, Willem J. H. Van Berkel

    Abstract:

    Abstract The flavoenzyme l -galactono-γ-lactone dehydrogenase (GALDH) catalyzes the terminal step of vitamin C biosynthesis in plants. Little is known about the catalytic mechanism of GALDH and related Aldonolactone oxidoreductases. Here we identified an essential Glu–Arg pair in the active site of GALDH from Arabidopsis thaliana . Glu386 and Arg388 variants show high K m values for l -galactono-1,4-lactone and low turnover rates. Arg388 is crucial for the stabilization of the anionic form of the reduced FAD cofactor. Glu386 is involved in productive substrate binding. The E386D variant has lost its specificity for l -galactono-1,4-lactone and shows the highest catalytic efficiency with l -gulono-1,4-lactone.

    Free Register to Access Article