Fungal glycogen synthesis and mobilisation

Fungi store glucose as glycogen, a branched alpha-1,4/alpha-1,6 glucan, through a UDP-glucose-dependent pathway like that of animals and unlike the ADP-glucose pathway of bacteria. Glucose 1-phosphate is activated with UTP to UDP-glucose by UDP-glucose pyrophosphorylase. Synthesis starts on glycogenin, a self-glucosylating GT-8 glucosyltransferase that attaches glucose to its own tyrosine residue(s) and extends a short alpha-1,4 oligosaccharide primer. Glycogen synthase (GT-3) elongates the primer by adding glucose from UDP-glucose to non-reducing ends, and the GH13 branching enzyme moves segments of chain to alpha-1,6 positions to create branches. Mobilisation has two routes. In the cytosol, glycogen phosphorylase releases glucose 1-phosphate from chain ends until it stops near a branch, and the bifunctional debranching enzyme transfers the remaining short branch to another chain (4-alpha-glucanotransferase) and hydrolyses the single alpha-1,6-linked glucose (amylo-alpha-1,6-glucosidase). Alternatively, glycogen delivered to the vacuole by autophagy is hydrolysed to free glucose by a vacuolar GH15 glucoamylase. Phosphoglucomutase interconverts glucose 1-phosphate and glucose 6-phosphate, linking both arms to glycolysis. Both arms are induced by nutrient limitation and stress and are controlled post-translationally (for example by phosphorylation of glycogen synthase and phosphorylase); these regulatory inputs are outside the module.

MODULE:glycogen_metabolism_fungalDRAFTCONCRETEMetabolic Pathwaymodules/glycogen_metabolism_fungal.yaml

glycogen metabolic processGO:0005977

GO:0005977

glycogen metabolic process

Module-level process concept covering synthesis and mobilisation.

GO:0005978

glycogen biosynthetic process

Process concept for the synthesis arm.

GO:0005980

glycogen catabolic process

Process concept for the mobilisation arm.

GO:0061723

glycophagy

Process concept for autophagic delivery of glycogen to the vacuole, the context of the vacuolar hydrolytic route.

YeastPathways:PWY3O-4031

glycogen biosynthesis (S. cerevisiae, SGD YeastPathways)

YeastCyc lists glycogenin self-glucosylation and primer extension (GLG1, GLG2), elongation (GSY1, GSY2), branching (GLC3), phosphoglucomutase (PGM1, PGM2) and UDP-glucose pyrophosphorylase (UGP1, YHL012W). All were retained except YHL012W, which is only a probable UDP-glucose pyrophosphorylase paralog.

YeastPathways:GLYCOCAT-YEAST-PWY

glycogen catabolism (S. cerevisiae, SGD YeastPathways)

YeastCyc lists GPH1 phosphorolysis, GDB1 transferase and alpha-1,6-glucosidase reactions, SGA1 glucoamylase and PGM1/PGM2. All gene assignments were retained. Two GDB1 reactions were not adopted: RXN3O-4038 (glycogen to maltotetraose, an isoamylase/GlgX-type reaction) and AMYLOMALT-RXN (maltotetraose + glucose disproportionation), which are not supported by the GDB1 characterisation.

PMID:11152943

Reserve carbohydrates metabolism in the yeast Saccharomyces cerevisiae.

Review of synthesis and degradation of glycogen and trehalose and their regulation in budding yeast (cited by YeastPathways for both glycogen frames).

In this review we present information on the regulation of the activity of the enzymes implicated in the pathways of synthesis and degradation of glycogen and trehalose

PMID:20412306

Regulation of glycogen metabolism in yeast and bacteria.

Comparative review of yeast and bacterial glycogen metabolism, including the role of the vacuole in yeast glycogen metabolism.

We also discuss our recent understanding of the important role played by the vacuole in glycogen metabolism.

PMID:8524228

Requirement of the self-glucosylating initiator proteins Glg1p and Glg2p for glycogen accumulation in Saccharomyces cerevisiae.

GLG1 and GLG2 encode self-glucosylating glycogenin-like primers; disruption of both abolishes glycogen synthesis despite normal glycogen synthase.

Disruption of both genes results in the inability of the cells to synthesize glycogen despite normal levels of glycogen synthase.

PMID:8900126

Initiation of glycogen synthesis in yeast. Requirement of multiple tyrosine residues for function of the self-glucosylating Glg proteins in vivo.

Glg2 is glycogen-associated and needs several tyrosine residues for function in vivo.

Unlike the mammalian counterpart, glycogenin, the yeast Glg proteins appear to require multiple Tyr residues for functionality.

PMID:16004992

Glycogen synthesis in the absence of glycogenin in the yeast Saccharomyces cerevisiae.

A small fraction of glg1 glg2 colonies switch on glycogen synthesis stochastically, so glycogenin priming is the normal but not the only initiation route.

we show that a small fraction of colonies from glg1glg2 mutants can switch on glycogen synthesis to levels comparable to wild-type strain.

PMID:1908457

Two glycogen synthase isoforms in Saccharomyces cerevisiae are coded by distinct genes that are differentially controlled.

GSY1 and GSY2 encode glycogen synthases; GSY2 is the predominant, nutrient-depletion-induced isoform.

The GSY2 gene product appears to be the predominant glycogen synthase with activity linked to nutrient depletion.

PMID:1634552

Coordinate regulation of glycogen metabolism in the yeast Saccharomyces cerevisiae. Induction of glycogen branching enzyme.

GLC3 encodes the glycogen branching enzyme.

Disruption of the branching enzyme structural gene establishes that branching enzyme activity is an absolute requirement for maximal glycogen synthesis.

PMID:2657401

Molecular analysis of GPH1, the gene encoding glycogen phosphorylase in Saccharomyces cerevisiae.

GPH1 encodes glycogen phosphorylase.

Haploid cells disrupted in GPH1 lacked phosphorylase activity and attained higher levels of intracellular glycogen

PMID:11094287

The Saccharomyces cerevisiae YPR184w gene encodes the glycogen debranching enzyme.

GDB1 encodes a bifunctional debranching enzyme with alpha-1,4-glucanotransferase and alpha-1,6-glucosidase activities.

Reliable measurement of alpha-1,4-glucanotransferase and alpha-1, 6-glucosidase activity of the yeast debranching enzyme was determined in strains overexpressing YPR184w.

PMID:2493265

Characterization and localization of the sporulation glucoamylase of Saccharomyces cerevisiae.

SGA1 glucoamylase degrades glycogen and is recovered in vacuolar fractions.

SGA was preferentially recovered in fractions which were enriched for the vacuolar hydrolases, carboxypeptidase Y and alpha-mannosidase.

PMID:11486014

Antagonistic controls of autophagy and glycogen accumulation by Snf1p, the yeast homolog of AMP-activated protein kinase, and the cyclin-dependent kinase Pho85p.

Autophagy mutants lose glycogen stores; Gph1 and the vacuolar Sga1 appear to degrade physically distinct pools of glycogen.

Gph1p and Sga1p may therefore degrade physically distinct pools of glycogen.

PMID:20383057

A vacuolar glucoamylase, Sga1, participates in glycogen autophagy for proper asexual differentiation in Magnaporthe oryzae.

In the filamentous fungus Magnaporthe oryzae, the vacuolar glucoamylase Sga1 and autophagy act together in vacuolar glycogen breakdown, generalising the vacuolar route beyond budding yeast.

Our results indicate that autophagy and Sga1 act cooperatively in vacuolar glycogen breakdown

12Nodes

9Parts

1Variant Sets

2Variants

9Annotons

8Connections

Derived QC

Recommended-field compliance

100.0% recommended fields populated

All recommended fields populated.

Module deep research

✗ none found

No MODULE:glycogen_metabolism_fungal deep-research report alongside the module YAML.

Leaf nodes lacking representative members

✓ every leaf node grounds to a representative protein.

Template conformance

✓ every declared conforms_to bundle matches its template motif.

Function consistency and core coverage

20 gene-function check(s) reflected in core functions · 0 conflict(s) · 1 evidence or coverage gap(s) (30 comparison(s))

Retained noncore functions are reported separately; they do not require promotion to core functions. Support from representative genes does not establish conservation across the whole family. Missing reviews or identifiers leave a claim unverified.

Annoton	Participant	Function	Assessment
ugp_activity	UGP1 (Saccharomyces cerevisiae) UniProtKB:P32861 Family Representative	UTP:glucose-1-phosphate uridylyltransferase activity GO:0003983	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ugp_activity	UGP2 (Homo sapiens) UniProtKB:Q16851 Family Representative	UTP:glucose-1-phosphate uridylyltransferase activity GO:0003983	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogenin_activity	GLG1 (Saccharomyces cerevisiae) UniProtKB:P36143 Family Representative	glycogenin glucosyltransferase activity GO:0008466	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogenin_activity	GLG2 (Saccharomyces cerevisiae) UniProtKB:P47011 Family Representative	glycogenin glucosyltransferase activity GO:0008466	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogenin_activity	GYG1 (Homo sapiens) UniProtKB:P46976 Family Representative	glycogenin glucosyltransferase activity GO:0008466	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogen_synthase_activity	GSY2 (Saccharomyces cerevisiae) UniProtKB:P27472 Family Representative	alpha-1,4-glucan glucosyltransferase (UDP-glucose donor) activity GO:0004373	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogen_synthase_activity	GSY1 (Saccharomyces cerevisiae) UniProtKB:P23337 Family Representative	alpha-1,4-glucan glucosyltransferase (UDP-glucose donor) activity GO:0004373	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogen_synthase_activity	GYS1 (Homo sapiens) UniProtKB:P13807 Family Representative	alpha-1,4-glucan glucosyltransferase (UDP-glucose donor) activity GO:0004373	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
branching_enzyme_activity	GLC3 (Saccharomyces cerevisiae) UniProtKB:P32775 Family Representative	1,4-alpha-glucan branching enzyme activity GO:0003844	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
branching_enzyme_activity	GBE1 (Homo sapiens) UniProtKB:Q04446 Family Representative	1,4-alpha-glucan branching enzyme activity GO:0003844	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogen_phosphorylase_activity	GPH1 (Saccharomyces cerevisiae) UniProtKB:P06738 Family Representative	glycogen phosphorylase activity GO:0008184	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
glycogen_phosphorylase_activity	PYGM (Homo sapiens) UniProtKB:P11217 Family Representative	glycogen phosphorylase activity GO:0008184	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
debranching_transferase_activity	GDB1 (Saccharomyces cerevisiae) UniProtKB:Q06625 Family Representative	4-alpha-glucanotransferase activity GO:0004134	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
debranching_transferase_activity	AGL (Homo sapiens) UniProtKB:P35573 Family Representative	4-alpha-glucanotransferase activity GO:0004134	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
debranching_glucosidase_activity	GDB1 (Saccharomyces cerevisiae) UniProtKB:Q06625 Family Representative	amylo-alpha-1,6-glucosidase activity GO:0004135	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
debranching_glucosidase_activity	AGL (Homo sapiens) UniProtKB:P35573 Family Representative	amylo-alpha-1,6-glucosidase activity GO:0004135	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
vacuolar_glucoamylase_activity	SGA1 (Saccharomyces cerevisiae) UniProtKB:P08019 Family Representative	glucan 1,4-alpha-glucosidase activity GO:0004339	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
phosphoglucomutase_activity	PGM2 (Saccharomyces cerevisiae) UniProtKB:P37012 Family Representative	phosphoglucomutase activity GO:0004614	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
phosphoglucomutase_activity	PGM1 (Saccharomyces cerevisiae) UniProtKB:P33401 Family Representative	phosphoglucomutase activity GO:0004614	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
phosphoglucomutase_activity	PGM1 (Homo sapiens) UniProtKB:P36871 Family Representative	phosphoglucomutase activity GO:0004614	Core Supported The GO molecular function is reflected in core_functions (exact term or a reviewed subclass).
ugp_activity	eukaryotic UDP-glucose pyrophosphorylase PANTHER:PTHR43511 Family	UTP:glucose-1-phosphate uridylyltransferase activity GO:0003983	Family Supported Family review supports GO:0003983 FAMILY_WIDE. This is the defining activity of the eukaryotic UDPGP type 1 family. All four modules that use the family assert it, with catalytic representatives: dolichol_phosphate_sugar_donor_supply (as SF4, with UGP1, fyu1 and UGP2), glycogen_metabolism_fungal (UGP1, UGP2), and glycogen_biosynthesis (UGP2). The only exception is the S. pombe paralog SPCC794.10, which PAINT records as diverged.
glycogenin_activity	glycogenin (GT-8) PANTHER:PTHR11183 Family	glycogenin glucosyltransferase activity GO:0008466	Family Scope Restricted GO:0008466 is SUBFAMILY_ONLY; this family grounding does not establish the allowed subfamily scope. Glycogenins only. glycogen_metabolism_fungal and glycogen_biosynthesis select the base family, which also takes in galactinol synthases, GUX and GNT1. Subfamily placements are from the PANTHER 19 classification files; the cached entries carry none.
glycogen_synthase_activity	eukaryotic GT-3 glycogen synthase PANTHER:PTHR10176 Family	alpha-1,4-glucan glucosyltransferase (UDP-glucose donor) activity GO:0004373	Family Supported Family review supports GO:0004373 FAMILY_WIDE. Asserted by glycogen_metabolism_fungal and glycogen_biosynthesis on the base family; accepted by every reviewed member in all three subfamilies.
branching_enzyme_activity	GH13 1,4-alpha-glucan branching enzyme PANTHER:PTHR43651:SF3 Family	1,4-alpha-glucan branching enzyme activity GO:0003844	Family Supported Family review supports GO:0003844 for PANTHER:PTHR43651:SF3. Asserted by glycogen_metabolism_fungal, glycogen_biosynthesis, tres_mak_glge_branched_alpha_glucan_biosynthesis and glycogen_synthesis_and_mobilization; accepted by GLC3. Restricted to the branching-enzyme clade PTN000040010; TreZ (SF11) lacks it.
glycogen_phosphorylase_activity	glycogen phosphorylase PANTHER:PTHR11468:SF3 Family	glycogen phosphorylase activity GO:0008184	Family Supported Family review supports GO:0008184 for PANTHER:PTHR11468:SF3. Glycogen phosphorylases (SF3, SF32, SF29, SF2), as glycogen_metabolism_fungal and glycogenolysis assert on the base family. Plant starch phosphorylases and MalP act on other glucans.
glycogen_phosphorylase_activity	glycogen phosphorylase PANTHER:PTHR11468:SF32 Family	glycogen phosphorylase activity GO:0008184	Family Supported Family review supports GO:0008184 for PANTHER:PTHR11468:SF32. Glycogen phosphorylases (SF3, SF32, SF29, SF2), as glycogen_metabolism_fungal and glycogenolysis assert on the base family. Plant starch phosphorylases and MalP act on other glucans.
debranching_transferase_activity	eukaryotic glycogen debranching enzyme PANTHER:PTHR10569 Family	4-alpha-glucanotransferase activity GO:0004134	Family Supported Family review supports GO:0004134 FAMILY_WIDE. Transferase half of the bifunctional enzyme; asserted by glycogen_metabolism_fungal and accepted by GDB1 and AGL.
debranching_glucosidase_activity	eukaryotic glycogen debranching enzyme PANTHER:PTHR10569 Family	amylo-alpha-1,6-glucosidase activity GO:0004135	Family Supported Family review supports GO:0004135 FAMILY_WIDE. Glucosidase half of the bifunctional enzyme; asserted by glycogen_metabolism_fungal and glycogenolysis and accepted by GDB1 and AGL.
vacuolar_glucoamylase_activity	intracellular sporulation-specific glucoamylase (GH15) PANTHER:PTHR31616:SF9 Family	glucan 1,4-alpha-glucosidase activity GO:0004339	Family Supported Family review supports GO:0004339 for PANTHER:PTHR31616:SF9. Glucoamylase subfamilies, as glycogen_metabolism_fungal selects SF9.
phosphoglucomutase_activity	phosphoglucomutase PANTHER:PTHR22573:SF2 Family	phosphoglucomutase activity GO:0004614	Family Supported Family review supports GO:0004614 FAMILY_WIDE. This is the defining activity of the bacterial, fungal, animal and plant PGMs. The five modules that use this family assert it with catalytic representatives (yeast PGM1/PGM2, S. pombe SPBC32F12.10, human PGM1): dolichol_phosphate_sugar_donor_supply, emp_glycolysis, galactose_leloir_pathway, glycogenolysis, and glycogen_metabolism_fungal (as SF2). The vertebrate PGM5 clade (SF27) is the exception, and PAINT already excludes it with an IKR.

Gene-review completeness (18/18 grounded genes reviewed)

16 complete review(s) · 11 with deep research · 0 missing review · 7 reviewed but lacking deep research

Gene	Review	Complete	Deep research
AGL P35573	✓	27/35	✗
GBE1 Q04446	✓	27/28	✗
GDB1 Q06625	✓	✓	✓
GLC3 P32775	✓	✓	✓
GLG1 P36143	✓	✓	✓
GLG2 P47011	✓	✓	✓
GPH1 P06738	✓	✓	✓
GSY1 P23337	✓	✓	✓
GSY2 P27472	✓	✓	✓
GYG1 P46976	✓	✓	✗
GYS1 P13807	✓	✓	✗
PGM1 P33401	✓	✓	✓
PGM1 P36871	✓	✓	✗
PGM2 P37012	✓	✓	✓
PYGM P11217	✓	✓	✗
SGA1 P08019	✓	✓	✓
UGP1 P32861	✓	✓	✓
UGP2 Q16851	✓	✓	✗

Tree

Fungal glycogen synthesis and mobilisationMetabolic Pathwayglycogen_metabolism_fungal

Parts
1. 1. glycogen synthesis
2. Glucose 1-phosphate to branched glycogenMetabolic Pathwayglycogen_synthesis
  
  Parts
  1. 1. UDP-glucose donor formation
  2. glucose 1-phosphate + UTP to UDP-glucose + diphosphateReactionudp_glucose_formation
    
    Annotons
    
    UDP-glucose pyrophosphorylase Family: eukaryotic UDP-glucose pyrophosphorylase
  3. 2. primer initiation by glycogenin
  4. glycogenin + n UDP-glucose to oligoglucosyl-glycogenin + n UDPReactionglycogenin_priming
    
    Annotons
    
    Self-glucosylating glycogenin Family: glycogenin (GT-8)
  5. 3. chain elongation
  6. glycogen(n) + UDP-glucose to glycogen(n+1) + UDPReactionglycogen_elongation
    
    Annotons
    
    UDP-glucose-dependent glycogen synthase Family: eukaryotic GT-3 glycogen synthase
  7. 4. branch formation
  8. linear alpha-1,4-glucan to alpha-1,6-branched glycogenReactionglycogen_branching
    
    Annotons
    
    Glycogen branching enzyme (GH13) Family: GH13 1,4-alpha-glucan branching enzyme
3. 2. glycogen mobilisation
4. Glycogen to glucose 1-phosphate or glucoseMetabolic Pathwayglycogen_mobilisation
  
  Variants
  1. Cytosolic phosphorolytic versus vacuolar hydrolytic glycogen degradation by route and compartment (One Or More)
    
    Cytosolic phosphorylase plus debranching enzymeMetabolic Pathwaycytosolic_phosphorolytic_route
    
    Parts
    
    1. phosphorolysis of alpha-1,4 chains
    
    glycogen(n) + phosphate to glycogen(n-1) + glucose 1-phosphateReactionglycogen_phosphorolysis
    
    Annotons
    
    Glycogen phosphorylase (GT-35) Family: glycogen phosphorylase
    
    2. debranching of limit dextrin
    
    alpha-limit dextrin to debranched chain + glucoseReactionglycogen_debranching
    
    Annotons
    
    Debranching enzyme 4-alpha-glucanotransferase domain Family: eukaryotic glycogen debranching enzyme
    
    Debranching enzyme amylo-alpha-1,6-glucosidase domain Family: eukaryotic glycogen debranching enzyme
    
    Vacuolar glucoamylase acting on autophagy-delivered glycogenReactionvacuolar_hydrolytic_route
    
    Annotons
    
    Vacuolar GH15 glucoamylase Family: intracellular sporulation-specific glucoamylase (GH15)
5. 3. hexose-phosphate interconversion linking glycogen to glycolysis
6. glucose 1-phosphate to/from glucose 6-phosphateReactionphosphoglucomutase_step
  
  Annotons
  - Phosphoglucomutase Family: phosphoglucomutase

Details

Context

fungiNCBITaxon:4751

Fungal glycogen synthesis and mobilisationMetabolic Pathwayglycogen_metabolism_fungal

glycogen metabolic processGO:0005977

Context

fungiNCBITaxon:4751

NEW module (YeastPathways crosswalk, 2026-10) generalising PWY3O-4031 and GLYCOCAT-YEAST-PWY into one fungal glycogen module with a synthesis arm, a mobilisation arm (cytosolic phosphorolytic versus vacuolar hydrolytic routes) and the shared phosphoglucomutase link. The synthesis arm and the cytosolic route conform to the human glycogen_biosynthesis and glycogenolysis modules (same GO MFs and PANTHER families for UGP, glycogenin, glycogen synthase, branching enzyme, phosphorylase, debranching enzyme and PGM); those human modules are disease-oriented and were not edited. The bacterial ADP-glucose route is in glycogen_synthesis_and_mobilization, and the animal lysosomal acid alpha-glucosidase route (GAA, GH31) in lysosomal_glycogen_degradation is analogous to, but not homologous with, the fungal vacuolar GH15 glucoamylase route. Changes to YeastCyc: (1) glycogenin GLG1/GLG2 were expected to be missing from YeastCyc, but the current PWY3O-4031 frame does list them (GLYCOGENIN-GLUCOSYLTRANSFERASE-RXN and RXN-7667); they are retained as the priming step and the two YeastCyc glycogenin reactions are merged into one GO:0008466 activity. Priming is required in practice, although rare glg1 glg2 colonies can make glycogen (PMID:16004992). (2) YHL012W is listed by YeastCyc as a second UDP-glucose pyrophosphorylase; UniProt describes it only as probable and no characterisation was found, so it is not used as an exemplar. (3) The GDB1 reactions RXN3O-4038 (glycogen to maltotetraose) and AMYLOMALT-RXN are not adopted: they describe bacterial isoamylase/GlgX and amylomaltase/MalQ chemistry, whereas GDB1 is an AGL-type transferase/glucosidase (PMID:11094287). (4) SGA1 is placed in the vacuole (PMID:2493265, PMID:11486014), not the cytosol. GO-CAM disagreements: the YeastPathways models type GPH1 and the GDB1 transferase and glycogenin primer-extension activities only with GO:0003674, and place SGA1 in the cytosol. No PomBase GO-CAM is linked; S. pombe is not used as an exemplar. Regulation (PKA, Snf1, Pho85, Gac1/Glc7 phosphatase, Rim15) and the glycogen-granule proteins are outside the module.

Connections

phosphoglucomutase_step -> udp_glucose_formation Provides Input For

Glucose 1-phosphate made from glucose 6-phosphate feeds UDP-glucose formation.

glycogen_synthesis -> glycogen_mobilisation Provides Input For

Stored glycogen is the substrate of both mobilisation routes.

glycogen_phosphorolysis -> phosphoglucomutase_step Provides Input For

Glucose 1-phosphate released by phosphorylase is converted to glucose 6-phosphate.

Part 1: glycogen synthesis

Glucose 1-phosphate to branched glycogenMetabolic Pathwayglycogen_synthesis

glycogen biosynthetic processGO:0005978

Connections

udp_glucose_formation -> glycogenin_priming Precedes

glycogenin_priming -> glycogen_elongation Precedes

glycogen_elongation -> glycogen_branching Precedes

Part 1: UDP-glucose donor formation

glucose 1-phosphate + UTP to UDP-glucose + diphosphateReactionudp_glucose_formation

Annotons

UDP-glucose pyrophosphorylase

ugp_activity

Participant: Family: eukaryotic UDP-glucose pyrophosphorylase

Family:

eukaryotic UDP-glucose pyrophosphorylasePANTHER:PTHR43511

Representative Members: UGP1 (Saccharomyces cerevisiae)UniProtKB:P32861 UGP2 (Homo sapiens)UniProtKB:Q16851

Required Function:

UTP:glucose-1-phosphate uridylyltransferase activityGO:0003983

Function

UTP:glucose-1-phosphate uridylyltransferase activityGO:0003983

Substrates: alpha-D-glucose 1-phosphate UTP

Products: UDP-alpha-D-glucose diphosphate

Locations

cytosolGO:0005829

Supplies the UDP-glucose donor used by glycogenin and glycogen synthase. UDP-glucose is shared with trehalose, beta-glucan and glycoconjugate synthesis, so this step is also part of the udp_glucose_and_udp_galactose_biosynthesis module.

Part 2: primer initiation by glycogenin

glycogenin + n UDP-glucose to oligoglucosyl-glycogenin + n UDPReactionglycogenin_priming

Annotons

Self-glucosylating glycogenin

glycogenin_activity

Participant: Family: glycogenin (GT-8)

Family:

glycogenin (GT-8)PANTHER:PTHR11183 Kept at family level. PANTHER 19.0 places GLG1 and GLG2 in SF100 and GYG1 in SF164, but SF100 also holds plant IPUT1-type GT8 glucuronosyltransferases, so a subfamily list would assert glycogenin activity for proteins that lack it.

Representative Members: GLG1 (Saccharomyces cerevisiae)UniProtKB:P36143 GLG2 (Saccharomyces cerevisiae)UniProtKB:P47011 GYG1 (Homo sapiens)UniProtKB:P46976

Required Function:

glycogenin glucosyltransferase activityGO:0008466

Function

glycogenin glucosyltransferase activityGO:0008466 Self-glucosylation of glycogenin tyrosine residue(s) and extension of the attached alpha-1,4 oligosaccharide primer. YeastCyc splits this into two reactions (GLYCOGENIN-GLUCOSYLTRANSFERASE-RXN and RXN-7667); both are covered by EC 2.4.1.186.

Substrates: UDP-alpha-D-glucose glycogenin tyrosine residue

Products: alpha-1,4-oligoglucosyl-glycogenin primer UDP

Locations

cytosolGO:0005829

Primes glycogen synthesis. glg1 glg2 double mutants make no glycogen except in rare stochastic glycogen-positive colonies (PMID:16004992).

Part 3: chain elongation

glycogen(n) + UDP-glucose to glycogen(n+1) + UDPReactionglycogen_elongation

Annotons

UDP-glucose-dependent glycogen synthase

glycogen_synthase_activity

Participant: Family: eukaryotic GT-3 glycogen synthase

Family:

eukaryotic GT-3 glycogen synthasePANTHER:PTHR10176

Representative Members: GSY2 (Saccharomyces cerevisiae)UniProtKB:P27472 GSY1 (Saccharomyces cerevisiae)UniProtKB:P23337 GYS1 (Homo sapiens)UniProtKB:P13807

Required Function:

alpha-1,4-glucan glucosyltransferase (UDP-glucose donor) activityGO:0004373

Function

alpha-1,4-glucan glucosyltransferase (UDP-glucose donor) activityGO:0004373

Substrates: UDP-alpha-D-glucose (1,4-alpha-D-glucosyl)n primer or glycogen chain

Products: (1,4-alpha-D-glucosyl)n+1 chain UDP

Locations

cytosolGO:0005829

Rate-limiting, phosphorylation-regulated elongation of alpha-1,4 chains from the glycogenin primer.

Part 4: branch formation

linear alpha-1,4-glucan to alpha-1,6-branched glycogenReactionglycogen_branching

Annotons

Glycogen branching enzyme (GH13)

branching_enzyme_activity

Participant: Family: GH13 1,4-alpha-glucan branching enzyme

Family:

GH13 1,4-alpha-glucan branching enzyme

Representative Members: GLC3 (Saccharomyces cerevisiae)UniProtKB:P32775 GBE1 (Homo sapiens)UniProtKB:Q04446

Required Function:

1,4-alpha-glucan branching enzyme activityGO:0003844

Function

1,4-alpha-glucan branching enzyme activityGO:0003844

Substrates: linear alpha-1,4-glucan chain

Products: alpha-1,6-branched glucan

Locations

cytosolGO:0005829

Introduces alpha-1,6 branch points; required for full glycogen accumulation.

Part 2: glycogen mobilisation

Glycogen to glucose 1-phosphate or glucoseMetabolic Pathwayglycogen_mobilisation

glycogen catabolic processGO:0005980

Variant set: Cytosolic phosphorolytic versus vacuolar hydrolytic glycogen degradation by route and compartment (One Or More)

Budding yeast uses both routes, on physically distinct glycogen pools (PMID:11486014). The cytosolic route conserves the glycosidic-bond energy as glucose 1-phosphate; the vacuolar route yields free glucose.

Cytosolic phosphorylase plus debranching enzymeMetabolic Pathwaycytosolic_phosphorolytic_route

Connections

glycogen_phosphorolysis -> glycogen_debranching Precedes

debranching_transferase_activity -> debranching_glucosidase_activity Precedes

Part 1: phosphorolysis of alpha-1,4 chains

glycogen(n) + phosphate to glycogen(n-1) + glucose 1-phosphateReactionglycogen_phosphorolysis

Annotons

Glycogen phosphorylase (GT-35)

glycogen_phosphorylase_activity

Participant: Family: glycogen phosphorylase

Family:

glycogen phosphorylase

Representative Members: GPH1 (Saccharomyces cerevisiae)UniProtKB:P06738 PYGM (Homo sapiens)UniProtKB:P11217

Required Function:

glycogen phosphorylase activityGO:0008184

Function

glycogen phosphorylase activityGO:0008184

Substrates: glycogen phosphate

Products: alpha-D-glucose 1-phosphate alpha-limit dextrin

Cofactors: pyridoxal 5'-phosphate

Locations

cytosolGO:0005829

Releases glucose 1-phosphate from non-reducing ends until about four residues from a branch point.

Part 2: debranching of limit dextrin

alpha-limit dextrin to debranched chain + glucoseReactionglycogen_debranching

One bifunctional enzyme performs two sequential activities: transfer of a maltosyl or maltotriosyl unit from the branch to another chain, then hydrolysis of the remaining alpha-1,6-linked glucose.

Annotons

Debranching enzyme 4-alpha-glucanotransferase domain

debranching_transferase_activity

Participant: Family: eukaryotic glycogen debranching enzyme

Family:

eukaryotic glycogen debranching enzymePANTHER:PTHR10569

Representative Members: GDB1 (Saccharomyces cerevisiae)UniProtKB:Q06625 AGL (Homo sapiens)UniProtKB:P35573

Required Function:

4-alpha-glucanotransferase activityGO:0004134

Function

4-alpha-glucanotransferase activityGO:0004134

Substrates: alpha-limit dextrin

Products: alpha-limit dextrin with single-glucose branches

Locations

cytosolGO:0005829

Moves the outer residues of a phosphorylase-trimmed branch onto a neighbouring chain; the yeast enzyme prefers maltosyl units.

Debranching enzyme amylo-alpha-1,6-glucosidase domain

debranching_glucosidase_activity

Participant: Family: eukaryotic glycogen debranching enzyme

Family:

eukaryotic glycogen debranching enzymePANTHER:PTHR10569

Representative Members: GDB1 (Saccharomyces cerevisiae)UniProtKB:Q06625 AGL (Homo sapiens)UniProtKB:P35573

Required Function:

amylo-alpha-1,6-glucosidase activityGO:0004135

Function

amylo-alpha-1,6-glucosidase activityGO:0004135

Substrates: alpha-limit dextrin with single-glucose branches water

Products: debranched alpha-limit dextrin D-glucose

Locations

cytosolGO:0005829

Hydrolyses the single alpha-1,6-linked glucose so phosphorylase can continue.

Vacuolar glucoamylase acting on autophagy-delivered glycogenReactionvacuolar_hydrolytic_route

glycophagyGO:0061723

Annotons

Vacuolar GH15 glucoamylase

vacuolar_glucoamylase_activity

Participant: Family: intracellular sporulation-specific glucoamylase (GH15)

Family:

intracellular sporulation-specific glucoamylase (GH15)PANTHER:PTHR31616:SF9 The parent PANTHER family PTHR31616 is named TREHALASE after other members; this subfamily holds SGA1.

Representative Members: SGA1 (Saccharomyces cerevisiae)UniProtKB:P08019

Required Function:

glucan 1,4-alpha-glucosidase activityGO:0004339

Function

glucan 1,4-alpha-glucosidase activityGO:0004339 Exo-hydrolysis of alpha-1,4 (and, more slowly, alpha-1,6) linkages from non-reducing ends, releasing beta-D-glucose.

Substrates: glycogen water

Products: D-glucose

Locations

fungal-type vacuoleGO:0000324

Hydrolyses glycogen delivered to the vacuole; prominent during sporulation in budding yeast and during conidiation in Magnaporthe oryzae (PMID:20383057).

Part 3: hexose-phosphate interconversion linking glycogen to glycolysis

glucose 1-phosphate to/from glucose 6-phosphateReactionphosphoglucomutase_step

Annotons

Phosphoglucomutase

phosphoglucomutase_activity

Participant: Family: phosphoglucomutase

Family:

phosphoglucomutasePANTHER:PTHR22573:SF2

Representative Members: PGM2 (Saccharomyces cerevisiae)UniProtKB:P37012 PGM1 (Saccharomyces cerevisiae)UniProtKB:P33401 PGM1 (Homo sapiens)UniProtKB:P36871

Required Function:

phosphoglucomutase activityGO:0004614

Function

phosphoglucomutase activityGO:0004614

Substrates: alpha-D-glucose 1-phosphate

Products: D-glucose 6-phosphate

Locations

cytosolGO:0005829

Reversible step that supplies glucose 1-phosphate for UDP-glucose formation and returns phosphorolysis-derived glucose 1-phosphate to glucose 6-phosphate and glycolysis. Shared with galactose and trehalose metabolism.