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  • Title: Role of Val289 residue in the alpha-amylase of Bacillus amyloliquefaciens MTCC 610: an analysis by site directed mutagenesis.
    Author: Priyadharshini R, Hemalatha D, Gunasekaran P.
    Journal: J Microbiol Biotechnol; 2010 Mar; 20(3):563-8. PubMed ID: 20372028.
    Abstract:
    The Val289 residue in the alpha-amylase of Bacillus amyloliquefaciens, which is equivalent to the Ala289 and Val286 residues in the alpha-amylases of B. stearothermophilus and B. licheniformis, respectively, was studied by site-directed mutagenesis. This residue was substituted with 10 different amino acids by random substitution of the Val codon. In these mutant alpha-amylases, Val289 was substituted with Ile, Tyr, Phe, Leu, Gly, Pro, Ser, Arg, Glu, and Asp. Compared with the wild-type alpha-amylase, the mutant alpha-amylase Val289Ile showed 20% more hydrolytic activity, whereas Val289Phe and Val289Leu showed 50% lesser activity. On the other hand, the mutant alpha-amylases Val289Gly, Val289Tyr, Val289Ser, and Val289Pro showed less than 15% activity. The substitution of Val289 with Arg, Asp, or Glu resulted in complete loss of the alpha-amylase activity. Interestingly, the mutant alpha-amylase Val289Tyr had acquired a transglycosylation activity, which resulted in the change of product profile of the reaction, giving a longer oligosaccharide.
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