Activation of aspartase by site-directed mutagenesis |
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Authors: | S Murase J S Takagi Y Higashi H Imaishi N Yumoto M Tokushige |
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Affiliation: | Department of Chemistry, Faculty of Science, Kyoto University, Japan. |
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Abstract: | To elucidate the role of sulfhydryl groups in the enzymatic reaction of the aspartase from Escherichia coli, we used site-directed mutagenesis which showed that the enzyme was activated by replacement of Cys-430 with a tryptophan. This mutation produced functional alterations without appreciable structural change: The kcat values became 3-fold at pH 6.0; the Hill coefficient values became higher under both pH conditions; the dependence of enzyme activity on divalent metal ions increased; and hydroxylamine, a good substrate for the wild-type enzyme, proved a poor substrate for the mutant. |
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