Alpha amylase catalytic domain found in the Glycogen branching enzyme (also called 1,4-alpha-glucan branching enzyme). The glycogen branching enzyme catalyzes the third step of glycogen biosynthesis by the cleavage of an alpha-(1,4)-glucosidic linkage and the formation a new alpha-(1,6)-branch by subsequent transfer of cleaved oligosaccharide. They are part of a group called branching enzymes which catalyze the formation of alpha-1,6 branch points in either glycogen or starch. This group includes proteins from bacteria, eukaryotes, and archaea. 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 protein GlgB.

alpha-1,4-glucan:alpha-1,4-glucan 6-glycosyltransferase. This model describes the glycogen branching enzymes which are responsible for the transfer of chains of approx. 7 alpha(1--4)-linked glucosyl residues to other similar chains (in new alpha(1--6) linkages) in the biosynthesis of glycogen. This enzyme is a member of the broader amylase family of starch hydrolases which fold as (beta/alpha)8 barrels, the so-called TIM-barrel structure. All of the sequences comprising the seed of this model have been experimentally characterized. This model encompasses both bacterial and eukaryotic species. No archaea have this enzyme, although Aquifex aolicus does. Two species, Bacillus thuringiensis and Clostridium perfringens have two sequences each which are annotated as amylases. These annotations are aparrently in error. GP|18143720 from C. perfringens, for instance, contains the note "674 aa, similar to gp:A14658_1 amylase (1,4-alpha-glucan branching enzyme (EC 2.4.1.18) ) from Bacillus thuringiensis (648 aa); 51.1% identity in 632 aa overlap." A branching enzyme from Porphyromonas gingivales, OMNI|PG1793, appears to be more closely related to the eukaryotic species (across a deep phylogenetic split) and may represent an instance of lateral transfer from this species' host. A sequence from Arabidopsis thaliana, GP|9294564, scores just above trusted, but appears either to contain corrupt sequence or, more likely, to be a pseudogene as some of the conserved catalytic residues common to the alpha amylase family are not conserved here. [Energy metabolism, Biosynthesis and degradation of polysaccharides]

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

1,4-alpha-glucan branching protein GlgB.

Crystalstructure of branching enzyme W610N mutant from Cyanothece sp. ATCC 51142 [Crocosphaera subtropica ATCC 51142],5GQX_A Crystal structure of branching enzyme W610N mutant from Cyanothece sp. ATCC 51142 in complex with maltoheptaose [Crocosphaera subtropica ATCC 51142]

Crystalstructure of branching enzyme W610A mutant from Cyanothece sp. ATCC 51142 [Crocosphaera subtropica ATCC 51142]

Crystalstructure of branching enzyme from Cyanothece sp. ATCC 51142 [Crocosphaera subtropica ATCC 51142],5GQV_A Crystal structure of branching enzyme from Cyanothece sp. ATCC 51142 in complex with maltohexaose [Crocosphaera subtropica ATCC 51142],5GQY_A Crystal structure of branching enzyme from Cyanothece sp. ATCC 51142 in complex with maltoheptaose [Crocosphaera subtropica ATCC 51142]

Crystalstructure of branching enzyme L541A mutant from Cyanothece sp. ATCC 51142 [Crocosphaera subtropica ATCC 51142],5GR4_A Crystal structure of branching enzyme L541A mutant from Cyanothece sp. ATCC 51142 in complex with maltoheptaose [Crocosphaera subtropica ATCC 51142]

ChainA, 1,4-alpha-glucan branching enzyme GlgB [Crocosphaera subtropica ATCC 51142]

1,4-alpha-glucan branching enzyme GlgB OS=Halothermothrix orenii (strain H 168 / OCM 544 / DSM 9562) OX=373903 GN=glgB PE=3 SV=1

1,4-alpha-glucan branching enzyme GlgB OS=Thermosynechococcus vestitus (strain IAM M-273 / NIES-2133 / BP-1) OX=197221 GN=glgB PE=3 SV=1

1,4-alpha-glucan branching enzyme GlgB OS=Aquifex aeolicus (strain VF5) OX=224324 GN=glgB PE=3 SV=1

1,4-alpha-glucan branching enzyme GlgB OS=Synechococcus sp. (strain JA-3-3Ab) OX=321327 GN=glgB PE=3 SV=1

1,4-alpha-glucan branching enzyme GlgB OS=Synechococcus sp. (strain JA-2-3B'a(2-13)) OX=321332 GN=glgB PE=3 SV=1