Kinetic studies of acid inactivation of alpha-amylase from Aspergillus oryzae

Morten Carlsen, Jens Bredal Nielsen, John Villadsen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The stability of alpha-amylase from Aspergillus oryzae has been studied at different pH. The enzyme is extremely stable at neutral pH (pH 5-8), whereas outside this pH-range a substantial loss of activity is observed. The acid-inactivation of alpha-amylase from A. oryzae was monitored on-line by a FIA-system. At low pH (pH<4.0) the inactivation follows first-order kinetics, and the rate constant is given by the empirical expression k = 1.19 x 10(7) [H+](1.99)(h(-1)) illustrating that the inactivation process is highly dependent of the pH in the medium. At pH 6 the acid-inactivated enzyme regains part of its activity, and the reactivation process also follows first-order kinetics. The irreversible loss of activity is found not to result from a protease contamination of the protein samples. A proposed model, where irreversibly inactivated a-amylase is formed both directly from the active enzyme and via the reversibly inactivated enzyme, describes the experimental data very well.
    Original languageEnglish
    JournalChemical Engineering Science
    Volume51
    Issue number1
    Pages (from-to)37-43
    ISSN0009-2509
    DOIs
    Publication statusPublished - 1996

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