Bacterial glycogen and related alpha-glucan metabolism

A reusable bacterial storage-carbon module that distinguishes canonical GlgC/ADP-glucose-dependent glycogen synthesis from Pseudomonas UDP-glucose-dependent production of linear alpha-glucan by GlgA. In Pseudomonas, most GlgA-derived linear glucan enters the TreY/TreZ and TreS-Mak-GlgE network. GlgB can branch GlgA-derived polymer, but that connection is modeled as an unverified capability whose physiological contribution is unknown. The mobilization arm represents GlgP phosphorolysis and GlgX branch removal, while leaving the physiological partitioning of these enzymes among bacterial glycogen and related branched alpha-glucan pools unresolved. The module ends at glucose 1-phosphate; phosphoglucomutase and central carbon metabolism are downstream.

This bacterial turnover module complements the existing glycogen biosynthesis and glycogenolysis modules; it does not replace their eukaryotic boundaries. Family selectors make the reaction roles reusable; representative members identify concrete implementations rather than restricting the module to PSEPK. KT2440 supplies exact GalU, GlgA, GlgB, GlgP, and GlgX exemplars. No GlgC or other EC 2.7.7.27 candidate is present in the current KT2440 UniProt metadata. Pseudomonas aeruginosa PAO1 has the same absence and its purified GlgA prefers UDP-glucose, so the Pseudomonas GalU/UDP-glucose route is modeled as a leading family-level hypothesis for linear glucan formation. GalU is a pleiotropic nucleotide-sugar supplier rather than a dedicated glycogen enzyme. Current curation supports UDP-glucose specificity by transfer from the assayed same-subfamily PAO1 ortholog while retaining direct Q88FN9 kinetics as a knowledge gap. The Pseudomonas linear product is routed primarily to neighboring TreY/TreZ and TreS-Mak-GlgE modules. The species-aware OpenScientist report's claim that the UDP-glucose route is unsupported is not retained because it missed the direct PAO1 GlgA donor assay in PMID:33872310.