Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • glucoamylase  (5)
  • Computational Chemistry and Molecular Modeling  (1)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 9-22 
    ISSN: 0006-3592
    Keywords: condensation reactions ; disaccharides ; equilibria ; glucoamylase ; kinetics ; monosaccharides ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Arabinose, fructose, galactose, myo-inositol, lyxose, mannose, ribose, and xylose were incubated individually and with glucose in the presence of Aspergillus niger glucoamylase at pH 4.5 and 45°C. Glucoamylase condenses galactose, glucose, and mannose individually into disaccharides. It also produces mixed disaccharides when each of the eight carbohydrates is incubated with glucose. Many products were identified by gas chromatography of the derivatized reaction mixtures followed by mass spectroscopy of the individual chromatographic peaks. Galacto-, gluco-, or mannopyranosyl rings appear to be present at the nonreducing ends of all the disaccharides produced. Molecules linked through primary hydroxyl groups have the highest equilibrium constants of all products formed, since these bonds are thermodynamically favored. However, glucoamylase is capable of forming bonds with many available hydroxyl groups, as previously demonstrated when it was incubated with glucose alone. Formation rates of different bonds linking different residues vary widely. These results demonstrate that glucoamylase has a wide selectivity toward residues it will condense into disaccharides and toward bonds it will form between them. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 9-22, 1997.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 27 (1997), S. 235-248 
    ISSN: 0887-3585
    Keywords: acarviosinide ; active site ; docking ; glucoamylase ; molecular mechanics ; monosaccharides ; simulated annealing ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Glucoamylase is an important industrial glucohydrolase with a large specificity range. To investigate its interaction with the monosaccharides D-glucose, D-mannose, and D-galactose and with the substrate analogues 1-deoxynojirimycin, D-glucono-1,5-lactone, and methyl αacarviosinide, MM3(92)-optimized structures were docked into its active site using AutoDock 2.1. The results were compared to structures of glucoamylase complexes obtained by protein crystallography. Charged forms of some substrate analogues were also docked to assess the degree of protonation possessed by glucoamylase inhibitors. Many forms of methyl αa-carviosinide were conformationally mapped by using MM3(92), characterizing the conformational pH dependence found for the acarbose family of glucosidase inhibitors. Their significant conformers, representing the most common states of the inhibitor, were used as initial structures for docking. This constitutes a new approach for the exploration of binding modes of carbohydrate chains. Docking results differ slightly from x-ray crystallographic data, the difference being of the order of the crystallographic error. The estimated energetic interactions, even though agreeing in some cases with experimental binding kinetics, are only qualitative due to the large approximations made by AudoDock force field. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 28 (1997), S. 162-173 
    ISSN: 0887-3585
    Keywords: AutoDock ; cellobioside ; disaccharide ; docking ; gentiobioside ; glucoamylase ; kojibioside ; maltoside ; nigeroside ; simulated annealing ; trehalose ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: To better understand the molecular basis of glucomylase selectivity, low-energy conformers of glucosyl disaccharides obtained from relaxed-residue conformational mapping were flexibly docked into the glucoamylase active site using AutoDock 2.2. This procedure ensures that significant conformational space is searched and can produce bound structures comparable to those obtained by protein crystallography. α-Linked glucosyl disaccharides except α,α-trehalose dock easily into the active site while exclusively β-linked disaccharides do not, explaining why only the former are glucoamylase substrates. The optimized docking modes are similar at the nonreducing end of the different substrates. Individual atomic energies of intermolecular interaction allow the definite identification of key hydroxyl groups for each substrate. This approach confirmed the versatility of the second subsite of the glucoamylase active site in binding different substrates. Proteins 28:162-173, 1997. © 1997 Wiley-Liss Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 29 (1997), S. 334-347 
    ISSN: 0887-3585
    Keywords: evolution ; glucoamylase ; hydrophobic folding ; protein parsimony analysis ; structure/function ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: To correlate structural features with glucoamylase properties, a structure-based multisequence alignment was constructed using information from catalytic and starch-binding domain models. The catalytic domain is composed of three hydrophobic folding units, the most labile and least hydrophobic of them being missing in the most stable glucoamylase. The role of O-glycosylation in stabilizing the most hydrophobic folding unit, the only one where thermostabilizing mutations with unchanged activity have been made, is described. Differences in both length and composition of interhelical loops are correlated with stability and selectivity characteristics. Two new glucoamylase subfamilies are defined by using homology criteria. Protein parsimony analysis suggests an ancient bacterial origin for the glucoamylase gene. Increases in length of the belt surrounding the active site, degree of O-glycosylation, and length of the linker probably correspond to evolutionary steps that increase stability and secretion levels of Aspergillus-related glucoamylases. Proteins 29:334-347, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 101-105 
    ISSN: 0006-3592
    Keywords: Aspergillus awamori ; glucoamylase ; kinetic ; thermostability ; Saccharomyces cerevisiae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Asn182 → Ala Aspergillus awamori glucoamylase expressed in Saccharomyces cerevisiae had a first-order thermodeactivation coefficient 40% that of wild-type glucoamylase at pH 4.5 between 60° and 65°C, caused by the elimination of an Asn - Gly sequence subject to deamidation and eventual chain breakage. Above 70°C, and at pHs 3.5 and 5.5, thermodeactivation coefficients of wild-type and mutant enzymes were roughly equal, because the fastest deactivation mechanism was no longer deamidation. The mutation had little effect on the enzyme's optimal pH for activity and subsite map, or on the glucose yield from starch dextrin hydrolysis. During enzyme production by yeast fermentation, highest cell densities and activities of wild-type and mutant glucoamylases were attained after a period of glucose starvation, followed by a second addition of glucose. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 13 (1992), S. 102-114 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Energy surfaces for the relative orientations of the pyranosyl rings of α,α-, α,β-, and β,β-trehalose and analogues were generated with MM3. Sixteen starting conformations of the rotatable side groups of α,β-trehalose were considered, while only 10 conformations were needed for α,α- and β,β-trehalose because of molecular symmetry. Energies were calculated at 20° increments of the two torsional angles of the glycosidic linkage, but otherwise the molecules were fully relaxed. The structure at the overall minimum for α,α-trehalose agrees well with that found in crystal structures, and also agrees with interpretations of NMR and optical rotation data. The energy surfaces for the three trehaloses differ greatly from each other, but are each similar to those for the corresponding three 2-(6-methyltetrahydropyran-2-yloxy)6-methyltetrahydropyrans. This suggests that linkage type (axial or equatorial) is more important than exocyclic substituents in determining trehalose conformations. A comparison with surfaces from the corresponding 5a-carba trehalose analogues illustrates that the exo-anomeric effect is important in determining disaccharide conformation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...