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  • Title: [Arg292----Val] or [Arg292----Leu] mutation enhances the reactivity of Escherichia coli aspartate aminotransferase with aromatic amino acids.
    Author: Hayashi H, Kuramitsu S, Inoue Y, Morino Y, Kagamiyama H.
    Journal: Biochem Biophys Res Commun; 1989 Feb 28; 159(1):337-42. PubMed ID: 2564274.
    Abstract:
    Arg292 of E. coli aspartate aminotransferase was substituted with valine or leucine by site-directed mutagenesis. In comparison with the wild-type enzyme, either of the mutant enzymes showed a decrease by over 5 orders of magnitude of kcat/km values for aspartate and glutamate. This supports the contention that Arg292 is important for determining the specificity of this enzyme for dicarboxylic substrates. In contrast, mutant enzymes displayed a 5- to 10-fold increase in kcat/Km values for aromatic amino acids as substrates. Thus, introduction of an uncharged, hydrophobic side chain into position 292 leads to a striking alteration in substrate specificity of this enzyme, thereby improving catalytic efficiency toward aromatic amino acids.
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