Alpha amylase catalytic domain found in glycogen debranching enzymes. Debranching enzymes facilitate the breakdown of glycogen through glucosyltransferase and glucosidase activity. These activities are performed by a single enzyme in mammals, yeast, and some bacteria, but by two distinct enzymes in Escherichia coli and other bacteria. Debranching enzymes perform two activities: 4-alpha-D-glucanotransferase (EC 2.4.1.25) and amylo-1,6-glucosidase (EC 3.2.1.33). 4-alpha-D-glucanotransferase catalyzes the endohydrolysis of 1,6-alpha-D-glucoside linkages at points of branching in chains of 1,4-linked alpha-D-glucose residues. Amylo-alpha-1,6-glucosidase catalyzes the endohydrolysis of 1,6-alpha-D-glucoside linkages at points of branching in chains of 1,4-linked alpha-D-glucose residues. In Escherichia coli, GlgX is the debranching enzyme and malQ is the 4-alpha-glucanotransferase. TreX, an archaeal glycogen-debranching enzyme has dual activities like mammals and yeast, but is structurally similar to GlgX. TreX exists in two oligomeric states, a dimer and tetramer. Isoamylase (EC 3.2.1.68) is one of the starch-debranching enzymes that catalyzes the hydrolysis of alpha-1,6-glucosidic linkages specific in alpha-glucans such as amylopectin or glycogen and their beta-limit dextrins. 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.

Pullulanase/glycogen debranching enzyme [Carbohydrate transport and metabolism].

glycogen debranching protein GlgX.

bifunctional glycogen debranching protein GlgX/4-alpha-glucanotransferase.

pullulanase, type I. Pullulan is an unusual, industrially important polysaccharide in which short alpha-1,4 chains (maltotriose) are connected in alpha-1,6 linkages. Enzymes that cleave alpha-1,6 linkages in pullulan and release maltotriose are called pullulanases although pullulan itself may not be the natural substrate. This family consists of pullulanases related to the subfamilies described in TIGR02102 and TIGR02103 but having a different domain architecture with shorter sequences. Members are called type I pullulanases.

StructureOf Pseudomonas Isoamylase [Pseudomonas amyloderamosa]

Crystalstructure of Glycogen Debranching enzyme TreX from Sulfolobus solfataricus [Saccharolobus solfataricus],2VNC_B Crystal structure of Glycogen Debranching enzyme TreX from Sulfolobus solfataricus [Saccharolobus solfataricus],2VR5_A Crystal structure of Trex from Sulfolobus Solfataricus in complex with acarbose intermediate and glucose [Saccharolobus solfataricus],2VR5_B Crystal structure of Trex from Sulfolobus Solfataricus in complex with acarbose intermediate and glucose [Saccharolobus solfataricus],2VUY_A Crystal structure of Glycogen Debranching exzyme TreX from Sulfolobus solfatarius [Saccharolobus solfataricus],2VUY_B Crystal structure of Glycogen Debranching exzyme TreX from Sulfolobus solfatarius [Saccharolobus solfataricus],7EAV_A Chain A, Glycogen debranching enzyme [Saccharolobus solfataricus],7EAV_B Chain B, Glycogen debranching enzyme [Saccharolobus solfataricus]

Crystalstructure of Glycogen Debranching Enzyme GlgX from Escherichia coli K-12 [Escherichia coli K-12]

CrystalStructure of Chlamydomonas reinhardtii Isoamylase 1 (ISA1) [Chlamydomonas reinhardtii],4J7R_B Crystal Structure of Chlamydomonas reinhardtii Isoamylase 1 (ISA1) [Chlamydomonas reinhardtii],4OKD_A Crystal Structure of Chlamydomonas reinhardtii Isoamylase 1 (ISA1) in complex with maltoheptaose [Chlamydomonas reinhardtii],4OKD_B Crystal Structure of Chlamydomonas reinhardtii Isoamylase 1 (ISA1) in complex with maltoheptaose [Chlamydomonas reinhardtii]

Pullulanasefrom Bacillus acidopullulyticus [Bacillus acidopullulyticus]

Isoamylase OS=Flavobacterium sp. OX=239 GN=iam PE=1 SV=1

Isoamylase OS=Pseudomonas amyloderamosa OX=32043 GN=iam PE=1 SV=3

Isoamylase OS=Pseudomonas sp. (strain SMP1) OX=72588 GN=iam PE=1 SV=1

Glycogen operon protein GlgX homolog OS=Mycobacterium bovis (strain ATCC BAA-935 / AF2122/97) OX=233413 GN=glgX PE=3 SV=1

Glycogen operon protein GlgX homolog OS=Mycobacterium tuberculosis (strain CDC 1551 / Oshkosh) OX=83331 GN=glgX PE=3 SV=1