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KMID : 0545120100200030563
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Journal of Microbiology and Biotechnology
2010 Volume.20 No. 3 p.563 ~ p.568
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Role of Val289 residue in the α-amylase of Bacillus amyloliquefaciens MTCC 610: An analysis by site directed mutagenesis
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Priyadharshini R.
Hemalatha D.
Gunasekaran P.
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Abstract
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The Val289 residue in the α-amylase of Bacillus amyloliquefaciens, which is equivalent to Ala289 and Val286 residues in the α-amylases of B. sterothermophilus and B. licheniformis respectively, was studied by site directed mutagenesis. This residue was substituted with ten different amino acids by random substitution. In these mutant α-amylases Val289 was substituted with Ile, Tyr, Phe, Leu, Gly, Pro, Ser, Arg, Glu and Asp. Compared to the wild type α-amylase the mutant α-amylase Val289Ile showed 20% more hydrolytic activity while Val289Phe and Val289Leu showed 50% lesser activity. On the other hand, the mutant α-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 α-amylase activity. Interestingly, one of the mutant α-amylase Val289Tyr had acquired a new transglycosylation activity which resulted in the change of product profile of the reaction giving longer oligosaccharide.
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KEYWORD
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Bacillus amyloliquefaciens, α-amylase, site directed mutagenesis, starch hydrolysis, transglycosylation
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