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Properties and applications of starch-converting enzymes of the alpha-amylase family

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Author: Maarel, M.J.E.C. van der · Veen, B. van der · Uitdehaag, J.C.M. · Leemhuis, H. · Dijkhuizen, L.
Institution: Centraal Instituut voor Voedingsonderzoek TNO
Source:Journal of Biotechnology, 94, 137-155
Identifier: 87736
Keywords: Nutrition · α-Amylase · Anti-staling of bread · Glycosylhydrolases · Starch industry · Starch-converting enzymes · Amino acids · Chemical bonds · Conformations · Crystallization · Enzymes · Hydrolysis · Mutagenesis · Substrates · X-ray crystallography · Amylopectin · Cyclodextrin · Cyclomaltodextrin glucanotransferase · Dextrin · Dipeptidyl carboxypeptidase · Fructose · Glucose · Glycosidase · Maltodextrin · Maltose · Maltotriose · Transferase · Bacterium · Crop · Enzyme active site · Enzyme conformation · Enzyme engineering · Enzyme mechanism · Enzyme specificity · Enzyme stability · Enzyme substrate complex · Enzyme synthesis · Food processing · Industrial production · Protein domain · Protein family · Site directed mutagenesis · Structure activity relation · Amino Acid Sequence · Biotechnology · Conserved Sequence · Glycoside Hydrolases · Glycosyltransferases · Models, Molecular · Molecular Sequence Data · Protein Conformation · Sequence Homology, Amino Acid · Substrate Specificity · Manihot esculenta · Solanum tuberosum · Triticum aestivum · Zea mays


Starch is a major storage product of many economically important crops such as wheat, rice, maize, tapioca, and potato. A large-scale starch processing industry has emerged in the last century. In the past decades, we have seen a shift from the acid hydrolysis of starch to the use of starch-converting enzymes in the production of maltodextrin, modified starches, or glucose and fructose syrups. Currently, these enzymes comprise about 30% of the world's enzyme production. Besides the use in starch hydrolysis, starch-converting enzymes are also used in a number of other industrial applications, such as laundry and porcelain detergents or as anti-staling agents in baking. A number of these starch-converting enzymes belong to a single family: the α-amylase family or family13 glycosyl hydrolases. This group of enzymes share a number of common characteristics such as a (β/α)8 barrel structure, the hydrolysis or formation of glycosidic bonds in the α conformation, and a number of conserved amino acid residues in the active site. As many as 21 different reaction and product specificities are found in this family. Currently, 25 three-dimensional (3D) structures of a few members of the α-amylase family have been determined using protein crystallization and X-ray crystallography. These data in combination with site-directed mutagenesis studies have helped to better understand the interactions between the substrate or product molecule and the different amino acids found in and around the active site. This review illustrates the reaction and product diversity found within the α-amylase family, the mechanistic principles deduced from structure-function relationship structures, and the use of the enzymes of this family in industrial applications.