GlgB (PP_4058) is a soluble 1,4-alpha-glucan branching enzyme that cleaves a segment from an alpha-1,4-glucan chain and transfers it to the C6 hydroxyl of a glucan acceptor, creating an alpha-1,6 branch. It branches glycogen or the related alpha-glucan produced by the neighboring TreSB-GlgE route.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0003824 catalytic activity | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: GlgB is catalytic, but this root term omits its branch-transfer reaction. Reason: GO:0003844 captures the substrate class and branch-forming activity, so the root catalytic term is redundant. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt DR GO; GO:0003844; F:1,4-alpha-glucan branching enzyme activity; IEA:UniProtKB-UniRule. |
| GO:0003844 1,4-alpha-glucan branching enzyme activity | IEA GO_REF:0000120 | ACCEPT | Summary: GlgB transfers an alpha-1,4-glucan segment to create an alpha-1,6 branch. Reason: The reviewed HAMAP record assigns EC 2.4.1.18, GlgB-specific InterPro/NCBIfam signatures, and conserved catalytic residues. The local PANTHER member table places Q88FN1 in the specifically named PTHR43651:SF3 branching-enzyme subfamily. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt Reaction=Transfers a segment of a (1->4)-alpha-D-glucan chain to a file:interpro/panther/PTHR43651/PTHR43651-entries.csv Q88FN1,"1,4-alpha-glucan branching enzyme GlgB" |
| GO:0004553 hydrolase activity, hydrolyzing O-glycosyl compounds | IEA GO_REF:0000002 | REMOVE | Summary: The InterPro mapping reflects a GH13 fold, but GlgB's net reaction transfers a glucan segment rather than hydrolyzing it. Reason: The reviewed EC 2.4.1.18 reaction is branch-forming glycosyl transfer without water as the acceptor. The generic hydrolase annotation is a fold-level overextension and conflicts with the specific reaction. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt Reaction=Transfers a segment of a (1->4)-alpha-D-glucan chain to a |
| GO:0005737 cytoplasm | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Cytoplasm is a correct, if broad, location for this soluble branching enzyme. Reason: GlgB is a soluble monomeric GH13 branching enzyme with no signal peptide or transmembrane segment, acting on intracellular alpha-glucan, so the TreeGrafter cytoplasm call is true. Redundancy with the more specific cytosol annotation, which is itself kept as non-core, is not grounds for rejection; the location is non-core because the branching activity and glycogen biosynthesis carry the informative content. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt DR GO; GO:0005829; C:cytosol; IEA:TreeGrafter. |
| GO:0005829 cytosol | IEA GO_REF:0000118 | KEEP AS NON CORE | Summary: Cytosol is compatible with a soluble intracellular branching enzyme. Reason: The location is computational but biologically appropriate and is the more precise of the two existing compartment annotations. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt DR GO; GO:0005829; C:cytosol; IEA:TreeGrafter. |
| GO:0005975 carbohydrate metabolic process | IEA GO_REF:0000120 | MARK AS OVER ANNOTATED | Summary: GlgB directly remodels an alpha-glucan carbohydrate polymer. Reason: The term is correct but much broader than glycogen/alpha-glucan biosynthesis, does not identify the branching reaction, and adds no information beyond the more specific process annotation. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt Catalyzes the formation of the alpha-1,6-glucosidic linkages |
| GO:0005978 glycogen biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: Formation of alpha-1,6 branches is a direct glycogen-biosynthetic step. Reason: The reviewed HAMAP pathway annotation explicitly assigns glycogen biosynthesis. This denotes GlgB participation in polymer branching and does not attribute TreSB precursor production or GlgE elongation to GlgB. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt PATHWAY: Glycan biosynthesis; glycogen biosynthesis. |
| GO:0043169 cation binding | IEA GO_REF:0000002 | MARK AS OVER ANNOTATED | Summary: A GH13 domain mapping predicts cation binding, but no cation is specified. Reason: The reviewed UniProt record contains no cofactor comment or cation-binding feature, and the local PANTHER data add no cation annotation. This broad InterPro fold-level mapping is therefore not informative for GlgB's supported branch-transfer function. |
| GO:0044042 glucan metabolic process | IEA GO_REF:0000117 | MARK AS OVER ANNOTATED | Summary: GlgB directly remodels alpha-glucan by introducing branch points. Reason: The term is correct but broad and redundant with the more informative glycogen biosynthetic process and branching-enzyme activity. Supporting Evidence: file:PSEPK/glgB/glgB-uniprot.txt Transfers a segment of a (1->4)-alpha-D-glucan chain |
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