Map Key
Generic Enzyme
Generic kinase
Protein kinase
Lipid kinase
Generic phosphatase
Protein phosphatase
Lipid phosphatase
Generic phospholipase
Generic protease
Metalloprotease
G-alpha
RAS - superfamily
G beta/gamma
Regulators (GDI, GAP, GEF)
Generic channel
Ligand-gated channel
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Transporter
Normal process
Pathological process
Positive effect
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Emerges in disease
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Organsim specific interaction

Generic binding protein
Receptor ligand
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DNA
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Compound
Inorganic ion
Predicted metabolite or user's structure
Reaction
Generic receptor
GPCR
Receptors with enzyme activity
Mitochondria
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Nucleus
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Normal process
Pathological process
Binding
Cleavage
Covalent modifications
Phosphorylation
Dephosphorylation
Transformation
Transport
Catalysis
Transcription regulation
MicroRNA binding
Competition
Influence on expression
Unspecified interactions
Pharmacological effect
Toxic effect
Group relation
Complex subunit
Similarity reaction
A complex or a group
Organism specific object

Glycogen metabolism


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Glycogen metabolism

Glycogen metabolism

The metabolic path for Glycogen starts with alfa-D-Glucose that isphosphorylated by a set of enzymes: Hexokinase 1 ( HXK1 ) [1], [2], [3], Hexokinase 2 ( HXK2 ) [4], [5],[6], Hexokinase 3 ( HXK3 ) [7], [6], [8], Glucokinase (hexokinase 4) ( HXK4 ) [9], [10],[11], [12], [13] andalpha-(D)-Glucose-6-phosphate is formed. Also, alpha-D-Glucose isisomerically transformed into beta-D-Glucose by Galactose mutarotase (aldose1-epimerase) ( GALM ) [14], [15], [16]. Beta-D-Glucose undergoes the same transformations that alpha-D-glucose underthe action of the same enzymes to form beta-(D)-Glucose-6-phosphate whichsubsequently takes another stereoisomerisation step toalpha-(D)-Glucose-6-phosphate. This step is catalyzed by Glucose phosphateisomerase ( GPI ) [17]. Phosphoglucomutase 1 ( PGMU ) catalyzesthe next isomerization of alpha-(D)-Glucose-6-phosphate leading to formation ofalpha-(D)-Glucose 1-phosphate [18], [19]. UDP isthen attached to alpha-(D)-Glucose 1-phosphate by UDP-glucose pyrophosphorylase 1( UGPA1 ) or UDP-glucose pyrophosphorylase 2 ( UGPA2 ) to formUDP-D-glucose [20], [21], [22], [23].

UDP-D-glucose polymerizes with (alpha-D-glucosyl-(1-4))n to formGlycogen. This step is catalyzed by Glucan (1,4-alpha-), branching enzyme 1 (GLGB ) [24], [25], [26], [27]. Onthe other hand, Glycogen synthase 1 (muscle) ( GYS1 ) and Glycogen synthase 2(liver) ( GYS2 ) can cleave UDP-D-glucose from Glycogen to release(alpha-D-glucosyl-(1-4))n [28], [29], [30],[31], [32]. A number of glycogen phosphorylases (Phosphorylase,glycogen, liver ( PYGL ), Phosphorylase, glycogen, brain ( PYGB ) andPhosphorylase, glycogen, muscle ( PYGM )) mediate phosphorolysis ofGlycogen, which is regarded as transfer of one sugar residue (alpha-D-glucose1-phosphate) from Glycogen to inorganic phosphate. As a result Glycogenchain decreased for one sugar moiety with formation of a reduced product(alpha-D-glucosyl-(1-4))(,n=3)-alpha-D-glucosyl-(1-6)*(glycogen). [33], [34], [35], [36], [37], [38]. Thisproduct is a substrate for Amylo-1, 6-glucosidase, 4-alpha-glucanotransferase - glycogendebranching enzyme ( GDE ) that fractionates the polymeric structure to form twometabolites: the main chain - alpha-D-glucosyl-(1-6)*(glycogen) and branch chainof Glycogen - (alpha-D-glucosyl-(1-4))(,n=3) [39], [40],[41], [42], [43]. GDE also affects both productsof the latter reaction. Alpha-D-glucosyl-(1-4))(,n=3) can be directlyrepolymerized to Glycogen; alpha-D-glucosyl-(1-6)*(glycogen) can befurther hydrolyzed giving alpha-D-Glucose as a product.[40], [41], [43].