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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 163-170 
    ISSN: 0006-3592
    Keywords: enzymes ; organic solvents ; alcohol inhibition ; activity coefficients ; substrate specificity ; rate-limiting step ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alcohol inhibition of the lipase B from Candida antarctica has been studied through two different approaches: using the same inhibitor (1-butanol) in different organic solvents and using different inhibitors (differing in chain length) in the same solvent. The competitive inhibition constant values obtained in each case correlate with the calculated activity coefficients of the substrate, suggesting that desolvation of the alcohol is the major force changed. Data dispersion observed using the second approach has been interpreted to come from contributions of enzyme-inhibitor interactions to the binding energy. On the other hand, deacylation has been found to be much less influenced by the solvent variation than the acylation step, despite of the fact that solvation of the substrate involved in this step (the alcohol) is expected to change more than for the ester. Concerning the specificity behavior of the enzyme, a bimodal pattern was observed for the deacylation rate dependence on the alcohol chain length, with the highest values for hexanol (C6) and decanol (C10). With regard to the ester specificity, ethyl caproate (C6) is the preferred one. These results have been confronted with those reported for the lipase from Candida rugosa. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59: 163-170, 1998.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 684-694 
    ISSN: 0006-3592
    Keywords: immobilized enzymes ; organic solvents ; mechanism ; kinetic studies ; microscopic rate constants ; rate-limiting step ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics of the immobilized lipase B from Candida antarctica have been studied in organic solvents. This enzyme has been shown to be slightly affected by the water content of the organic media, and it does not seem to be subject to mass transfer limitations. On the other hand, some evidence indicates that the catalytic mechanism of reactions catalyzed by this lipase proceeds through the acyl-enzyme intermediate. Moreover, despite the fact that the immobilization support dramatically enhances the catalytic power of the enzyme, it does not interfere with the intrinsic solvent effect. Consequently, this enzyme preparation becomes optimum for studying the role played by the organic solvent in catalysis. To this end, we have measured the acylation and deacylation individual rate constants, and the binding equilibrium constant for the ester, in several organic environments. Data obtained show that the major effect of the organic solvent is on substrate binding, and that the catalytic steps are almost unaffected by the solvent, indicating the desolvation of the transition state. However, the strong decrease in binding for hydrophilic solvents such as THF and dioxane, compared to the rest of solvents, cannot be easily explained by means of thermodynamic arguments (desolvation of the ester substrate). For this reason, data have been considered as an indication of the existence of an unknown step in the catalytic pathway occurring prior to formation of the acyl-enzyme intermediate. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:684-694, 1998.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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