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  • 1.
    Bennett, Neil A.
    et al.
    Institute of Food Research.
    Ryan, James
    Institute of Food Research.
    Biely, Peter
    Slovak Academy of Sciences, Bratislava.
    Vrsanska, Maria
    Slovak Academy of Sciences, Bratislava.
    Kremnicky, Lubomir
    Slovak Academy of Sciences, Bratislava.
    Macris, Basil J.
    National Technical University of Athens.
    Kekos, Dimitris
    National Technical University of Athens.
    Christakopoulos, Paul
    Katapodis, Petros
    National Technical University of Athens.
    Claeyssens, Marc
    University of Ghent.
    Nerinckx, Wim
    University of Ghent.
    Ntauma, Patricia
    University of Ghent.
    Bhat, Mahalingeshwara K.
    Institute of Food Research.
    Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Thermomyces lanuginosus ATCC 468821998In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 306, no 3, p. 445-455Article in journal (Refereed)
    Abstract [en]

    An endoxylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) from the culture filtrates of T. lanuginosus ATCC 46882 was purified to homogeneity by DEAE-Sepharose and Bio-Gel P-30 column chromatographies. The purified endoxylanase had a specific activity of 888.8 mumol min-1 mg-1 protein and accounted for approximately 30% of the total protein secreted by this fungus. The molecular mass of native (non-denatured) and denatured endoxylanase were 26.3 and 25.7 kD as, respectively. Endoxylanase had a pI of 3.7 and was optimally active between pH 6.0-6.5 and at 75 degrees C. The enzyme showed > 50% of its original activity between pH 5.5-9.0 and at 85 degrees C. The pH and temperature stability studies revealed that this endoxylanase was almost completely stable between pH 5.0-9.0 and up to 60 degrees C for 5 h and at pH 10.0 up to 55 degrees C for 5 h. Thin-layer chromatography (TLC) analysis showed that endoxylanase released mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-D-glucuronoxylan, O-acetyl-4-O-methyl-D-glucuronoxylan and rhodymenan (a beta-(1-->3)-beta(1-->4)-xylan). Also, the enzyme released an acidic xylo-oligosaccharide from 4-O-methyl-D-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. The enzyme hydrolysed [1-3H]-xylo-oligosaccharides in an endofashion, but the hydrolysis of [1-3H]-xylotriose appeared to proceed via transglycosylation. since the xylobiose was the predominant product. Endoxylanase was not active on pNPX and pNPC at 40 and 100 mM for up to 6 h, but showed some activity toward pNPX at 100 mM after 20-24 h. The results suggested that the endoxylanase from T. lanuginosus belongs to family 11.

  • 2. Christakopoulos, Paul
    et al.
    Kekos, Dimitris
    National Technical University of Athens.
    Macris, Basil J.
    National Technical University of Athens.
    Claeyssens, Marc
    University of Ghent.
    Bhat, Mahalingeshwara K.
    Institute of Food Research.
    Purification and characterisation of a major xylanase with cellulase and transferase activities from Fusarium oxysporum1996In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 289, p. 91-104Article in journal (Refereed)
    Abstract [en]

    A major xylanase from Fusarium oxysporum was purified to homogeneity by gel filtration, affinity, and ion-exchange chromatographies. It has a molecular mass of 60.2 kDa and pl of 6.6 and was optimally active at pH 7.4 and at 50 °C. The enzyme was stable over the pH range 5.8–8.2 at 40 °C for 24 h and lost 45% of its original activity at pH 9.0 under the identical conditions. The enzyme rapidly hydrolysed xylans from oat spelts (husks) and birchwood, but the activities on carboxymethylcellulose (CMC), filter paper, and Avicel were very low. Determination of kcat/Km revealed that the enzyme hydrolysed oat spelts and birchwood xylans, 15–30 times more efficiently than CMC. In a 24 h incubation, at pH 7.0 and 9.0, the enzyme hydrolysed oat spelts and birchwood xylans by 75 and 65%, respectively. However, at pH 7.0, the enzyme released almost equal amounts of xylose and xylobiose from both xylans, whereas at pH 9.0, the concentration of xylobiose was twice as muchi as that of xylose and xylotriose. Xylanase attacked preferentially the internal glycosidic bonds of xylo- and 4-methylumbelliferyl cello-oligosaccharides [MeUmb(Glc)n]. The enzyme catalysed transglycosylation reaction with xylotriose, xylotetraose, and xylopentaose as donors and 4-methylumbelliferyl β-d-glucoside (MeUmbGlc) as an acceptor.

  • 3. Christakopoulos, Paul
    et al.
    Kourentzi, Ekaterini
    National Technical University of Athens.
    Hatzinikolaou, Dimitris G.
    National Technical University of Athens.
    Claeyssens, Mark
    University of Ghent.
    Kekos, Dimitris
    National Technical University of Athens.
    Macris, Basil J.
    National Technical University of Athens.
    Enhancement of pH-stability of a low molecular mass endoglucanase from Fusarium oxysporum by protein pegylation1998In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 314, no 1-2, p. 95-99Article in journal (Refereed)
    Abstract [en]

    The stability of the low molecular mass endoglucanase (23.2 kDa) from Fusarium oxysporum at alkaline pH was enhanced by chemical modification. Two distinct types of amino acid-specific modifiers were used. The first, either cyanuric chloride activated polyethylene glycol (CC–PEG) or polyethylene glycol succinimidyl succinate active ester (SS–PEG), react (more or less specifically) with protein amino groups. The second type, maleimide polyethylene glycol (Mal–PEG), is specific for cysteinyl residues. The enzyme lost almost all of its activity when modified with CC–PEG, whereas no inactivation was observed with SS–PEG and Mal–PEG. The modified endoglucanase showed remarkably enhanced alkaline pH stability. When acting upon cello-oligosaccharides and 4-methylumbelliferyl cello-oligosaccharides, the enzyme preferentially cleaved the internal glycosidic bonds. The modified enzymes mediated a decrease in the viscosity of carboxymethyl cellulose (CMC) associated with the release of only small amounts of reducing sugar. Thus, the modified enzyme retains the endo character of the native enzyme

  • 4. Christakopoulos, Paul
    et al.
    Nerinckx, Wim
    University of Ghent.
    Kekos, Dimitris
    National Technical University of Athens.
    Macris, Basil
    National Technical University of Athens.
    Claeyssens, Marc
    University of Ghent.
    The alkaline xylanase III from Fusarium oxysporum F3 belongs to family F/101997In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 302, no 3-4, p. 191-195Article in journal (Refereed)
    Abstract [en]

    Xylanase III from Fusarium oxysporum F3 was purified to homogeneity by ion-exchange chromatography and gel filtration. The enzyme has a molecular mass of 38 kDa, an isoelectric point of 9.5, and is maximally active on oat spelt xylan at pH 7 and 45 °C with a Km of 0.8 mg/mL. The xylanase displays remarkable stability at pH 9.0. It is not active on xylotriose but hydrolyzes the 4-methylumbelliferyl glycosides of β-xylobiose and --- , and to a lower extent 4-methylumbelliferyl β-cellobioside. When acted on xylooligosaccharides and xylan, analysis of reaction mixtures by high-pressure liquid chromatography shows preferred internal glycoside cleavage. Thus the purified enzyme appears to be a true endo-β-1,4-xylanase. Partial amino acid analysis of xylanase III shows high sequence homology with xylanases of family F/10.Xylanase III from Fusarium oxysporum F3 was purified to homogeneity by ion-exchange chromatography and gel filtration, and was functionally characterised. The enzyme displays remarkable stability at pH 9.0, appears to be a true endo-β-1,4-xylanase, and shows high sequence homology with xylanases of family F/10.

  • 5.
    Katapodis, Petros
    et al.
    National Technical University of Athens.
    Vrsanska, Maria
    Slovak Academy of Sciences, Bratislava.
    Kekos, Dimitris
    National Technical University of Athens.
    Nerinckx, Wim
    Ghent University.
    Biely, Peter
    Slovak Academy of Sciences, Bratislava.
    Claeyssens, Marc
    Ghent University.
    Macris, Basil J.
    National Technical University of Athens.
    Christakopoulos, Paul
    Biochemical and catalytic properties of an endoxylanase purified from the culture filtrate of Sporotrichum thermophile2003In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 338, no 18, p. 1881-1890Article in journal (Refereed)
    Abstract [en]

    An endo-β-1,4-xylanase (1,4-β-d-xylan xylanoxydrolase, EC 3.2.1.8) present in culture filtrates of Sporotrichum thermophile ATCC 34628 was purified to homogeneity by Q-Sepharose and Sephacryl S-200 column chromatographies. The enzyme has a molecular mass of 25,000 Da, an isoelectric point of 6.7, and is optimally active at pH 5 and at 70 °C. Thin-layer chromatography (TLC) analysis showed that endo-xylanase liberates mainly xylose (Xyl) and xylobiose (Xyl2) from beechwood 4-O-methyl-d-glucuronoxylan, O-acetyl-4-O-methylglucuronoxylan and rhodymenan (a β-(1→4)-β(1→3)-xylan). Also, the enzyme releases an acidic xylo-oligosaccharide from 4-O-methyl-d-glucuronoxylan, and an isomeric xylotetraose and an isomeric xylopentaose from rhodymenan. Analysis of reaction mixtures by high performance liquid chromatography (HPLC) revealed that the enzyme cleaves preferentially the internal glycosidic bonds of xylooligosaccharides, [1-3H]-xylooligosaccharides and xylan. The enzyme also hydrolyses the 4-methylumbelliferyl glycosides of β-xylobiose and β-xylotriose at the second glycosidic bond adjacent to the aglycon. The endoxylanase is not active on pNPX and pNPC. The enzyme mediates a decrease in the viscosity of xylan associated with a release of only small amounts of reducing sugar. The enzyme is irreversibly inhibited by series of ω-epoxyalkyl glycosides of d-xylopyranose. The results suggest that the endoxylanase from S. thermophile has catalytic properties similar to the enzymes belonging to family 11.

  • 6.
    Kong, Na
    et al.
    Royal Institute of Technology, Department of Chemistry.
    Shimpi, Manishkumar
    Royal Institute of Technology, Department of Chemistry.
    Park, Jae Hyeung
    Department of Chemistry, University of Massachusetts, Lowell.
    Ramström, Olof
    Organic Chemistry, School of Chemical Science and Engineering, KTH – Royal Institute of Technology, Stockholm, Royal Institute of Technology, Department of Chemistry.
    Yan, Mingdi
    Royal Institute of Technology, Department of Chemistry.
    Carbohydrate conjugation through microwave-assisted functionalization of single-walled carbon nanotubes using perfluorophenyl azides2015In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 405, p. 33-38Article in journal (Refereed)
    Abstract [en]

    Carbohydrate-functionalized single-walled carbon nanotubes (SWNTs) were synthesized using microwave-assisted reaction of perfluorophenyl azide with the nanotubes. The results showed that microwave radiation provides a rapid and effective means to covalently attach carbohydrates to SWNTs, producing carbohydrate-SWNT conjugates for biorecognition. The carbohydrate-functionalized SWNTs were furthermore shown to interact specifically with cognate carbohydrate-specific proteins (lectins), resulting in predicted recognition patterns. The carbohydrate-presenting SWNTs constitute a new platform for sensitive protein-or cell recognition, which pave the way for glycoconjugated carbon nanomaterials in biorecognition applications.

  • 7.
    Vafiadi, Christina
    et al.
    National Technical University of Athens.
    Topakas, Evangelos
    National Technical University of Athens.
    Christakopoulos, Paul
    Regioselective esterase-catalyzed feruloylation of L-arabinobiose2006In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 341, no 12, p. 1992-1997Article in journal (Refereed)
    Abstract [en]

    The regioselective chemoenzymatic synthesis of O-[5-O-(trans-feruloyl)-α-l-arabinofuranosyl]-(1→5)-l-arabinofuranose has been achieved. The reaction parameters affecting the feruloylation rate and conversion of the enzymatic synthesis, such as the composition of the reaction medium, substrate and enzyme concentration, have been investigated.

1 - 7 of 7
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