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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Bioscience reports 4 (1984), S. 613-619 
    ISSN: 1573-4935
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Bacillus amyloliquefaciens α-amylase activity is pH-dependent and the plot log (Vmax/Km) versus pH implicated a carboxyl group of aspartic acid/glutamic acid at the active site. Chemical modification of α-amylase with EDC confirmed this view. Further, analysis of inactivation kinetics showed that modification of a single carboxyl group led to complete loss of the enzymic activity.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 66 (1985), S. 13-20 
    ISSN: 1573-4919
    Keywords: active site ; α-amylase ; Bacillus amyloliquefaciens ; chemical modification ; diethylpyrocarbonate ; histidine ; rose bengal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Modification of liquefying α-amylase by diethylpyrocarbonate or its photo-oxidation in the presence of rose bengal caused rapid loss of enzyme activity. The photo-oxidation followed pseudo-first-order kinetics giving maximal value at pH 8.0. The photo-oxidized enzyme showed a characteristic increase in absorbance at 250 nm which was directly proportional to the extent of inactivation. Diethylpyrocarbonate at low concentration at pH 6.0 and 30 ° C completely inactivated a-amylase. Inactivation followed pseudo-first-order kinetics. The reaction order with respect to inactivation by diethylpyrocarbonate was one, thus indicating modification of a single histidine per mole of the enzyme. Diethylpyrocarbonate-modified enzyme showed increased absorbance at 240 nm which was reversed completely upon treatment with NH2OH at 30 °C for 16 hr. Calculating the histidine residues being modified from the increase in absorbance at 240 nm showed that three residues were ethoxyformylated on treatment with diethylpyrocarbonate, of which only one was found at the active site. Substrate and competitive inhibitor protects the enzyme against both, photo-oxidation, and modification by diethylpyrocarbonate, confirming that histidine plays an essential role at the α-amylase active site.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 675-680 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The copolymer styrene-maleic anhydride (SMA) was activated to various forms to create enzyme coupling groups. Carboxypeptidase A (CPA) was Immobilized on these supports to enhance their thermal and chemical stability. Immobilized enzyme retained 60-70% of the original activity. When kept at 60°C, while free enzyme was deactivated within 30 min, the immobilized enzyme retained 40% of initial activity at the end of 3 h. The half-life of free enzyme was only 21 min, while for immobilized enzyme it was enhanced up to 3 h. Also, the immobilized enzyme could be repeatedly used over 50 times retaining almost 50% of original activity.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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