glgP

UniProt ID: Q88CY8
Organism: Pseudomonas putida KT2440
Review Status: DRAFT
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Gene Description

GlgP (PP_5041) is a predicted pyridoxal-5'-phosphate-dependent alpha-1,4-glucan phosphorylase. It phosphorolytically shortens glycogen or related alpha-1,4 glucans to release alpha-D-glucose 1-phosphate, acting with a debranching enzyme during polymer mobilization. The precise KT2440 substrate preference and allosteric regulation have not been experimentally established.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0004645 1,4-alpha-oligoglucan phosphorylase activity
IEA
GO_REF:0000120 		ACCEPT
Summary: This term captures the alpha-1,4-glucan phosphorolysis chemistry.
Reason: Q88CY8 is assigned EC 2.4.1.1/RHEA:41732, which releases alpha-D-glucose 1-phosphate from an alpha-1,4-glucan chain.
Supporting Evidence:
file:PSEPK/glgP/glgP-uniprot.txt
Reaction=[(1->4)-alpha-D-glucosyl](n) + phosphate = [(1->4)-alpha-D-
GO:0005737 cytoplasm
IEA
GO_REF:0000118 		KEEP AS NON CORE
Summary: Cytoplasmic localization is compatible with a soluble glycogen enzyme.
Reason: The TreeGrafter location is biologically plausible but is not a defining catalytic property and lacks direct localization evidence in KT2440.
Supporting Evidence:
file:PSEPK/glgP/glgP-uniprot.txt
DR GO; GO:0005737; C:cytoplasm; IEA:TreeGrafter.
GO:0005975 carbohydrate metabolic process
IEA
GO_REF:0000002 		KEEP AS NON CORE
Summary: Alpha-glucan phosphorolysis is carbohydrate metabolism, but this term is broad.
Reason: The term is valid context; glycogen catabolic process is the more informative pathway annotation.
Supporting Evidence:
file:PSEPK/glgP/glgP-uniprot.txt
Phosphorylase is an important allosteric enzyme in
GO:0005977 glycogen metabolic process
IEA
GO_REF:0000117 		KEEP AS NON CORE
Summary: The broad glycogen process is compatible with the GlgP assignment.
Reason: Q88CY8 is predicted to mobilize rather than synthesize glycogen, so the child glycogen catabolic process is the core pathway role.
Supporting Evidence:
file:PSEPK/glgP/glgP-uniprot.txt
glycogen catabolism, the phosphorolytic cleavage of glycogen to produce
GO:0005980 glycogen catabolic process
IEA
GO_REF:0000118 		ACCEPT
Summary: GlgP phosphorolysis directly mobilizes glycogen chain segments.
Reason: The RuleBase (RU000587) glycogen-phosphorylase family assignment and its function statement support a direct role in glycogen catabolism, while the imported claim that this is rate-limiting in KT2440 is not adopted. Experimental support comes from the P. aeruginosa PAO1 homolog, whose deletion increased alpha-glucan accumulation (PMID:33872310); that is evidence about the homolog, applied here by family membership.
Supporting Evidence:
file:PSEPK/glgP/glgP-uniprot.txt
glycogen catabolism, the phosphorolytic cleavage of glycogen to produce
file:PSEPK/glgP/glgP-uniprot.txt
Belongs to the glycogen phosphorylase family.
PMID:33872310
Thus, GlgP is a glycogen phosphorylase whose absence leads to the increased accumulation of trehalose and Ξ±-glucan in vivo.
GO:0008184 glycogen phosphorylase activity
IEA
GO_REF:0000120 		ACCEPT
Summary: The family-level annotation specifies glycogen as the alpha-glucan substrate.
Reason: Q88CY8 belongs to the glycogen phosphorylase family (RuleBase RU000587, InterPro IPR011833, NCBIfam TIGR02093) and carries the expected EC 2.4.1.1 reaction. The purified P. aeruginosa homolog released alpha-glucose 1-phosphate from maltohexaose (PMID:33872310); that is evidence about the homolog. Direct assays are still needed to measure selectivity among KT2440 alpha-glucans.
Supporting Evidence:
file:PSEPK/glgP/glgP-uniprot.txt
Belongs to the glycogen phosphorylase family.
file:PSEPK/glgP/glgP-uniprot.txt
DR InterPro; IPR011833; Glycg_phsphrylas.
PMID:33872310
Thus, GlgP is a glycogen phosphorylase whose absence leads to the increased accumulation of trehalose and Ξ±-glucan in vivo.
GO:0030170 pyridoxal phosphate binding
IEA
GO_REF:0000120 		KEEP AS NON CORE
Summary: PLP binding is a conserved cofactor property of glycogen phosphorylases.
Reason: UniProt predicts pyridoxal 5'-phosphate as the cofactor and identifies the corresponding family attachment-site signature, but cofactor binding is ancillary to the catalytic phosphorolysis annotation.
Supporting Evidence:
file:PSEPK/glgP/glgP-uniprot.txt
Name=pyridoxal 5'-phosphate; Xref=ChEBI:CHEBI:597326;

Core Functions

PLP-dependent phosphorolysis of alpha-1,4-glucan chain ends to release alpha-D-glucose 1-phosphate during storage-glucan mobilization. The substrate-neutral MF is used because KT2440 contains multiple connected alpha-glucan pools and Q88CY8 substrate preference is untested.

Molecular Function:
1,4-alpha-oligoglucan phosphorylase activity
Directly Involved In:
glycogen catabolic process
Supporting Evidence:
  • file:PSEPK/glgP/glgP-uniprot.txt
    Reaction=[(1->4)-alpha-D-glucosyl](n) + phosphate = [(1->4)-alpha-D-
  • PMID:33872310
    Thus, GlgP is a glycogen phosphorylase whose absence leads to the increased accumulation of trehalose and Ξ±-glucan in vivo.

References

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Suggested Questions for Experts

Q: Which KT2440 alpha-glucan pool is the preferred in-vivo substrate of GlgP?

Suggested Experiments

Experiment: Measure Q88CY8 kinetics on GlgA/GlgB-derived glycogen and TreS-Mak-GlgE-derived alpha-glucan, test candidate allosteric effectors, and quantify polymer mobilization in a glgP deletion strain.

πŸ“š Additional Documentation

Notes

(glgP-notes.md)

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