Alpha amylase catalytic domain found in bacterial and eukaryotic branching enzymes. Branching enzymes (BEs) catalyze the formation of alpha-1,6 branch points in either glycogen or starch by cleavage of the alpha-1,4 glucosidic linkage yielding a non-reducing end oligosaccharide chain, and subsequent attachment to the alpha-1,6 position. By increasing the number of non-reducing ends, glycogen is more reactive to synthesis and digestion as well as being more soluble. This group includes bacterial and eukaryotic proteins. 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.

1,4-alpha-glucan-branching enzyme

alpha-amylase

alpha-amylase; Provisional

1,4-alpha-glucan branching enzyme [Carbohydrate transport and metabolism].

Crystalstructure of human glycogen branching enzyme (GBE1) [Homo sapiens],4BZY_B Crystal structure of human glycogen branching enzyme (GBE1) [Homo sapiens],4BZY_C Crystal structure of human glycogen branching enzyme (GBE1) [Homo sapiens]

Structureof the Starch Branching Enzyme I (BEI) from Oryza sativa L [Oryza sativa Japonica Group]

Structureof the Starch Branching Enzyme I (BEI) complexed with maltopentaose from Oryza sativa L [Oryza sativa Japonica Group],3VU2_B Structure of the Starch Branching Enzyme I (BEI) complexed with maltopentaose from Oryza sativa L [Oryza sativa Japonica Group]

Structureof the Starch Branching Enzyme I (BEI) from Oryza sativa L [Oryza sativa Japonica Group]

ChainA, Isoform 2 of 1,4-alpha-glucan-branching enzyme, chloroplastic/amyloplastic [Oryza sativa Japonica Group]

1,4-alpha-glucan-branching enzyme OS=Rhizophagus irregularis (strain DAOM 181602 / DAOM 197198 / MUCL 43194) OX=747089 GN=GLC3 PE=2 SV=2

1,4-alpha-glucan-branching enzyme OS=Felis catus OX=9685 GN=GBE1 PE=2 SV=1

1,4-alpha-glucan-branching enzyme OS=Mus musculus OX=10090 GN=Gbe1 PE=1 SV=1

1,4-alpha-glucan-branching enzyme OS=Equus caballus OX=9796 GN=GBE1 PE=1 SV=1

1,4-alpha-glucan-branching enzyme OS=Homo sapiens OX=9606 GN=GBE1 PE=1 SV=3