Alpha amylase catalytic domain family; 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; and 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 this 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.

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gi 530722675  20 LSLWSHPLGAHGGEIEDDEMEA 41
Cdd:cd06595  232 YSWWSHDIGGHKGGIEDPELYL 253

glycosyl hydrolase family 31 (GH31); uncharacterized subgroup; This family represents an uncharacterized GH31 enzyme subgroup found in bacteria and eukaryotes. Enzymes of the GH31 family possess a wide range of different hydrolytic activities including alpha-glucosidase (glucoamylase and sucrase-isomaltase), alpha-xylosidase, 6-alpha-glucosyltransferase, 3-alpha-isomaltosyltransferase and alpha-1,4-glucan lyase. All GH31 enzymes cleave a terminal carbohydrate moiety from a substrate that varies considerably in size, depending on the enzyme, and may be either a starch or a glycoprotein.

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                 ....*....|....*....|..
gi 530722675  20 LSLWSHPLGAHGGEIEDDEMEA 41
Cdd:cd06595  232 YSWWSHDIGGHKGGIEDPELYL 253

glycosyl hydrolase family 31 (GH31); uncharacterized subgroup; This family represents an uncharacterized GH31 enzyme subgroup found in bacteria and eukaryotes. Enzymes of the GH31 family possess a wide range of different hydrolytic activities including alpha-glucosidase (glucoamylase and sucrase-isomaltase), alpha-xylosidase, 6-alpha-glucosyltransferase, 3-alpha-isomaltosyltransferase and alpha-1,4-glucan lyase. All GH31 enzymes cleave a terminal carbohydrate moiety from a substrate that varies considerably in size, depending on the enzyme, and may be either a starch or a glycoprotein.

                         10        20
                 ....*....|....*....|..
gi 530722675  20 LSLWSHPLGAHGGEIEDDEMEA 41
Cdd:cd06595  232 YSWWSHDIGGHKGGIEDPELYL 253