Plant Molecular Biology

, Volume 25, Issue 2, pp 141–157 | Cite as

Protein engineering in the α-amylase family: catalytic mechanism, substrate specificity, and stability

  • Birte Svensson


Most starch hydrolases and related enzymes belong to the α-amylase family which contains a characteristic catalytic (β/α)8-barrel domain. Currently known primary structures that have sequence similarities represent 18 different specificities, including starch branching enzyme. Crystal structures have been reported in three of these enzyme classes: the α-amylases, the cyclodextrin glucanotransferases, and the oligo-1,6-glucosidases. Throughout the α-amylase family, only eight amino acid residues are invariant, seven at the active site and a glycine in a short turn. However, comparison of three-dimensional models with a multiple sequence alignment suggests that the diversity in specificity arises by variation in substrate binding at the β→α loops. Designed mutations thus have enhanced transferase activity and altered the oligosaccharide product patterns of α-amylases, changed the distribution of α-, β- and γ-cyclodextrin production by cyclodextrin glucanotransferases, and shifted the relative α-1,4:α-1,6 dual-bond specificity of neopullulanase. Barley α-amylase isozyme hybrids and Bacillus α-amylases demonstrate the impact of a small domain B protruding from the (β/α)8-scaffold on the function and stability. Prospects for rational engineering in this family include important members of plant origin, such as α-amylase, starch branching and debranching enzymes, and amylomaltase.


Starch Oligosaccharide Cyclodextrin Protein Engineering Transferase Activity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.



cyclodextrin glucanotransferase


starch binding domain


taka-amylase A


triose-phosphate isomerase. The mutations are described with the one-letter code, i.e. D164A is a mutant in which A in the mutant is substituted for D in the wild-type.


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© Kluwer Academic Publishers 1994

Authors and Affiliations

  • Birte Svensson
    • 1
  1. 1.Department of ChemistryCarlsberg LaboratoryValbyDenmark

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