Alpha amylase catalytic domain found in bacterial Alpha-amylases (also called 1,4-alpha-D-glucan-4-glucanohydrolase). AmyA (EC 3.2.1.1) catalyzes the hydrolysis of alpha-(1,4) glycosidic linkages of glycogen, starch, related polysaccharides, and some oligosaccharides. This group includes Chloroflexi, Dictyoglomi, and Fusobacteria. The Alpha-amylase family comprises the largest family of glycoside hydrolases (GH), with the majority of enzymes acting on starch, glycogen, and related oligo- and polysaccharides. These proteins catalyze the transformation of alpha-1,4 and alpha-1,6 glucosidic linkages with retention of the anomeric center. The protein is described as having 3 domains: A, B, C. A is a (beta/alpha) 8-barrel; B is a loop between the beta 3 strand and alpha 3 helix of A; C is the C-terminal extension characterized by a Greek key. The majority of the enzymes have an active site cleft found between domains A and B where a triad of catalytic residues (Asp, Glu and Asp) performs catalysis. Other members of this family have lost the catalytic activity as in the case of the human 4F2hc, or only have 2 residues that serve as the catalytic nucleophile and the acid/base, such as Thermus A4 beta-galactosidase with 2 Glu residues (GH42) and human alpha-galactosidase with 2 Asp residues (GH31). The family members are quite extensive and include: alpha amylase, maltosyltransferase, cyclodextrin glycotransferase, maltogenic amylase, neopullulanase, isoamylase, 1,4-alpha-D-glucan maltotetrahydrolase, 4-alpha-glucotransferase, oligo-1,6-glucosidase, amylosucrase, sucrose phosphorylase, and amylomaltase.

Alpha amylase catalytic domain found in Trehalose synthetase. Trehalose synthetase (TreS) catalyzes the reversible interconversion of trehalose and maltose. The enzyme catalyzes the reaction in both directions, but the preferred substrate is maltose. Glucose is formed as a by-product of this reaction. It is believed that the catalytic mechanism may involve the cutting of the incoming disaccharide and transfer of a glucose to an enzyme-bound glucose. This enzyme also catalyzes production of a glucosamine disaccharide from maltose and glucosamine. The Alpha-amylase family comprises the largest family of glycoside hydrolases (GH), with the majority of enzymes acting on starch, glycogen, and related oligo- and polysaccharides. These proteins catalyze the transformation of alpha-1,4 and alpha-1,6 glucosidic linkages with retention of the anomeric center. The protein is described as having 3 domains: A, B, C. A is a (beta/alpha) 8-barrel; B is a loop between the beta 3 strand and alpha 3 helix of A; C is the C-terminal extension characterized by a Greek key. The majority of the enzymes have an active site cleft found between domains A and B where a triad of catalytic residues (Asp, Glu and Asp) performs catalysis. Other members of this family have lost the catalytic activity as in the case of the human 4F2hc, or only have 2 residues that serve as the catalytic nucleophile and the acid/base, such as Thermus A4 beta-galactosidase with 2 Glu residues (GH42) and human alpha-galactosidase with 2 Asp residues (GH31). The family members are quite extensive and include: alpha amylase, maltosyltransferase, cyclodextrin glycotransferase, maltogenic amylase, neopullulanase, isoamylase, 1,4-alpha-D-glucan maltotetrahydrolase, 4-alpha-glucotransferase, oligo-1,6-glucosidase, amylosucrase, sucrose phosphorylase, and amylomaltase.

Glycosidase [Carbohydrate transport and metabolism].

Alpha amylase catalytic domain found in cyclomaltodextrinases and related proteins. Cyclomaltodextrinase (CDase; EC3.2.1.54), neopullulanase (NPase; EC 3.2.1.135), and maltogenic amylase (MA; EC 3.2.1.133) catalyze the hydrolysis of alpha-(1,4) glycosidic linkages on a number of substrates including cyclomaltodextrins (CDs), pullulan, and starch. These enzymes hydrolyze CDs and starch to maltose and pullulan to panose by cleavage of alpha-1,4 glycosidic bonds whereas alpha-amylases essentially lack activity on CDs and pullulan. They also catalyze transglycosylation of oligosaccharides to the C3-, C4- or C6-hydroxyl groups of various acceptor sugar molecules. Since these proteins are nearly indistinguishable from each other, they are referred to as cyclomaltodextrinases (CMDs). The Alpha-amylase family comprises the largest family of glycoside hydrolases (GH), with the majority of enzymes acting on starch, glycogen, and related oligo- and polysaccharides. These proteins catalyze the transformation of alpha-1,4 and alpha-1,6 glucosidic linkages with retention of the anomeric center. The protein is described as having 3 domains: A, B, C. A is a (beta/alpha) 8-barrel; B is a loop between the beta 3 strand and alpha 3 helix of A; C is the C-terminal extension characterized by a Greek key. The majority of the enzymes have an active site cleft found between domains A and B where a triad of catalytic residues (Asp, Glu and Asp) performs catalysis. Other members of this family have lost the catalytic activity as in the case of the human 4F2hc, or only have 2 residues that serve as the catalytic nucleophile and the acid/base, such as Thermus A4 beta-galactosidase with 2 Glu residues (GH42) and human alpha-galactosidase with 2 Asp residues (GH31). The family members are quite extensive and include: alpha amylase, maltosyltransferase, cyclodextrin glycotransferase, maltogenic amylase, neopullulanase, isoamylase, 1,4-alpha-D-glucan maltotetrahydrolase, 4-alpha-glucotransferase, oligo-1,6-glucosidase, amylosucrase, sucrose phosphorylase, and amylomaltase.

Alpha amylase catalytic domain found in Sucrose isomerases, oligo-1,6-glucosidase (also called isomaltase; sucrase-isomaltase; alpha-limit dextrinase), dextran glucosidase (also called glucan 1,6-alpha-glucosidase), and related proteins. The sucrose isomerases (SIs) Isomaltulose synthase (EC 5.4.99.11) and Trehalose synthase (EC 5.4.99.16) catalyze the isomerization of sucrose and maltose to produce isomaltulose and trehalulose, respectively. Oligo-1,6-glucosidase (EC 3.2.1.10) hydrolyzes the alpha-1,6-glucosidic linkage of isomaltooligosaccharides, pannose, and dextran. Unlike alpha-1,4-glucosidases (EC 3.2.1.20), it fails to hydrolyze the alpha-1,4-glucosidic bonds of maltosaccharides. Dextran glucosidase (DGase, EC 3.2.1.70) hydrolyzes alpha-1,6-glucosidic linkages at the non-reducing end of panose, isomaltooligosaccharides and dextran to produce alpha-glucose.The common reaction chemistry of the alpha-amylase family enzymes is based on a two-step acid catalytic mechanism that requires two critical carboxylates: one acting as a general acid/base (Glu) and the other as a nucleophile (Asp). Both hydrolysis and transglycosylation proceed via the nucleophilic substitution reaction between the anomeric carbon, C1 and a nucleophile. Both enzymes contain the three catalytic residues (Asp, Glu and Asp) common to the alpha-amylase family as well as two histidine residues which are predicted to be critical to binding the glucose residue adjacent to the scissile bond in the substrates. The Alpha-amylase family comprises the largest family of glycoside hydrolases (GH), with the majority of enzymes acting on starch, glycogen, and related oligo- and polysaccharides. These proteins catalyze the transformation of alpha-1,4 and alpha-1,6 glucosidic linkages with retention of the anomeric center. The protein is described as having 3 domains: A, B, C. A is a (beta/alpha) 8-barrel; B is a loop between the beta 3 strand and alpha 3 helix of A; C is the C-terminal extension characterized by a Greek key. The majority of the enzymes have an active site cleft found between domains A and B where a triad of catalytic residues performs catalysis. Other members of this family have lost the catalytic activity as in the case of the human 4F2hc, or only have 2 residues that serve as the catalytic nucleophile and the acid/base, such as Thermus A4 beta-galactosidase with 2 Glu residues (GH42) and human alpha-galactosidase with 2 Asp residues (GH31). The family members are quite extensive and include: alpha amylase, maltosyltransferase, cyclodextrin glycotransferase, maltogenic amylase, neopullulanase, isoamylase, 1,4-alpha-D-glucan maltotetrahydrolase, 4-alpha-glucotransferase, oligo-1,6-glucosidase, amylosucrase, sucrose phosphorylase, and amylomaltase.

Crystalstructure of alpha-amylase from H.orenii [Halothermothrix orenii]

ChainA, Pullulanase type II, GH13 family [Thermococcus kodakarensis]

Structureof dextran glucosidase with glucose [Streptococcus mutans UA159],4XB3_A Structure of dextran glucosidase [Streptococcus mutans UA159]

ChainA, Dextran glucosidase [unidentified]

ChainA, Dextran glucosidase [unidentified]

Glucan 1,6-alpha-glucosidase OS=Streptococcus pneumoniae serotype 4 (strain ATCC BAA-334 / TIGR4) OX=170187 GN=dexB PE=3 SV=2

Alpha-amylase OS=Priestia megaterium OX=1404 PE=1 SV=1

Trehalose-6-phosphate hydrolase OS=Bacillus subtilis (strain 168) OX=224308 GN=treA PE=1 SV=2

Glucan 1,6-alpha-glucosidase OS=Streptococcus mutans serotype c (strain ATCC 700610 / UA159) OX=210007 GN=dexB PE=1 SV=2

Oligo-1,6-glucosidase OS=Weizmannia coagulans OX=1398 GN=malL PE=3 SV=1