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  • Title: Identification of glutamate residues important for catalytic activity of Bacillus stearothermophilus leucine aminopeptidase II.
    Author: Yang HL, Chen RS, Chen W, Lin LL.
    Journal: Antonie Van Leeuwenhoek; 2006 Aug; 90(2):195-9. PubMed ID: 16820970.
    Abstract:
    Each of four conserved glutamate residues of Bacillus stearothermophilus leucine aminopeptidase II (BsLAPII) was replaced with aspartate, lysine, and leucine respectively by site-directed mutagenesis. The over-expressed wild-type and mutant enzymes were purified to homogeneity by nickel-chelate chromatography and the molecular mass of the subunit was determined to be 44.5 kDa by SDS-PAGE. The specific activity for the Glu-316 and Glu-340 mutants was completely abolished, while Glu-249 mutants showed comparable activity to that of the wild-type BsLAPII. Compared with the wild-type enzyme, the E250D and E250L mutant enzymes retained less than 18% of the enzyme activity and exhibited a dramatic decrease in the value of k (cat)/K (m). These observations indicate that Glu-250, Glu-316, and Glu-340 residues are critical for the catalytic activity of BsLAPII.
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