Amylolytic enzymes: molecular aspects of their properties.
The present review describes the structural features of alpha-amylase, beta-amylase and glucoamylase that are the best known amylolytic enzymes. Although they show similar function, i.e. catalysis of hydrolysis of alpha-glucosidic bonds in starch and related saccharides, they are quite different. alpha-Amylase is the alpha --> alpha retaining glycosidase (it uses the retaining mechanism), and beta-amylase together with glucoamylase are the alpha --> beta inverting glycosidases (they use the inverting mechanism). While beta-amylase and glucoamylase form their own families 14 and 15, respectively, in the sequence-based classification of glycoside hydrolases, alpha-amylase belongs to a large clan of three families 13, 70 and 77 consisting of almost 30 different specificities. Structurally both alpha-amylase and beta-amylase rank among the parallel (beta/alpha)8-barrel enzymes, glucoamylase adopts the helical (alpha/alpha)6-barrel fold. The catalytic (beta/alpha)8-barrels of alpha-amylase and beta-amylase differ from each other. The only common sequence-structural feature is the presence of the starch-binding domain responsible for the binding and ability to digest raw starch. It is, however, present in about 10% of amylases and behaves as an independent evolutionary module. A brief discussion on structure-function and structure-stability relationships of alpha-amylases and related enzymes is also provided.
Horváthová
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Department of Biotechnologies, Faculty of Natural Sciences, University of SS Constantine and Methodius, Trnava, Slovakia.
Janecek
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Sturdík
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D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D002384:Catalysis; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry*; D006868:Hydrolysis; D008956:Models, Chemical; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D000516:alpha-Amylases / Q000737:chemistry*; D001614:beta-Amylase / Q000737:chemistry*
D001426:Bacterial Proteins; D000516:alpha-Amylases; D001614:beta-Amylase; D005087:Glucan 1,4-alpha-Glucosidase