glycogen debranching enzyme GlgX. This family consists of the GlgX protein from the E. coli glycogen operon and probable equivalogs from other prokaryotic species. GlgX is not required for glycogen biosynthesis, but instead acts as a debranching enzyme for glycogen catabolism. This model distinguishes GlgX from pullanases and other related proteins that also operate on alpha-1,6-glycosidic linkages. In the wide band between the trusted and noise cutoffs are functionally similar enzymes, mostly from plants, that act similarly but usually are termed isoamylase. [Energy metabolism, Biosynthesis and degradation of polysaccharides]

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.

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]

StructureOf Pseudomonas Isoamylase [Pseudomonas amyloderamosa]

Pullulanasefrom Bacillus acidopullulyticus [Bacillus acidopullulyticus]

Glycogen operon protein GlgX homolog OS=Mycobacterium tuberculosis (strain ATCC 25618 / H37Rv) OX=83332 GN=glgX 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

Glycogen debranching enzyme OS=Escherichia fergusonii (strain ATCC 35469 / DSM 13698 / CCUG 18766 / IAM 14443 / JCM 21226 / LMG 7866 / NBRC 102419 / NCTC 12128 / CDC 0568-73) OX=585054 GN=glgX PE=3 SV=1

Glycogen debranching enzyme OS=Erwinia tasmaniensis (strain DSM 17950 / CFBP 7177 / CIP 109463 / NCPPB 4357 / Et1/99) OX=465817 GN=glgX PE=3 SV=1