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Abstract (Expand)

Introduction: Phosphoglucomutases (PGM) are crucial for bacterial fitness, environmental survival, pathogenicity, and cell envelope stability, making them potential new targets for combating bacterialting bacterial infection and transmission. PGM functionality relies on initial phosphorylation by the activator glucose-1,6-bisphosphate (glucose-1,6-BP). While the origin of glucose-1,6-BP in vertebrates is well investigated, a bacterial glucose-1,6-BP synthase was only recently identified in the cyanobacterium Synechocystis. In this photoautotroph, a secondary PGM (SynPGM2) efficiently catalyzes glucose-1,6-BP synthesis from fructose-1,6-bisphosphate (fructose-1,6-BP) and glucose-1-phosphate or glucose-6-phosphate . A homologous PGM from the heterotrophic Bacteroides salyersiae, belonging to the same conserved domain subfamily (cd05800) as SynPGM2, exhibited similar activity, suggesting that bacterial glucose-1,6-BP synthesis is a feature of this specific subfamily. Methods: To investigate the specificity and regulation of various PGM enzymes from different heterotrophic bacteria, recombinant enzymes were purified and analyzed using enzymatic assays and HPLC-MS. Results: We demonstrate that glucose-1,6-BP synthesis extends beyond the cd5800 subfamily to the cd05801, cd05799, and cd03089 subfamilies. PGMs from Escherichia coli (cd05801 and cd03089), Enterococcus faecium (cd05799), Yersinia enterocolitica (cd05801), and Candidatus Gastranaerophilales (cd05800) catalyze the same fructose-1,6-BP-dependent synthesis reaction of glucose-1,6-BP as SynPGM2. Notably, fructose-1,6-BP, a known inhibitor of some PGM, does not inhibit these bacterial PGMs. Moreover, E. faecium PGM, belonging to the same subfamily as the mammalian glucose 1,6 BP synthase, efficiently catalyzes the mammalian-type 1,3-bisphosphoglycerate-dependent glucose 1,6-BP synthesis reaction. Conclusion: All investigated heterotrophic bacteria appear to use their primary PGM for both PGM activity and activator synthesis, suggesting a more versatile and less specialized role for PGMs in heterotrophic bacteria.

Authors: Janette T. Alford, Marina Borisova-Mayer, Christoph Mayer, Karl Forchhammer

Date Published: 16th Jul 2025

Publication Type: Journal

Abstract (Expand)

Regulation of glycogen metabolism is of vital importance in organisms of all three kingdoms of life. Although the pathways involved in glycogen synthesis and degradation are well known, many regulatory aspects around the metabolism of this polysaccharide remain undeciphered. Here, we used the unicellular cyanobacterium Synechocystis as a model to investigate how glycogen metabolism is regulated in dormant nitrogen-starved cells, which entirely rely on glycogen catabolism to restore growth. We found that the activity of the enzymes involved in glycogen synthesis and degradation is tightly controlled at different levels via post-translational modifications. Phosphorylation of phosphoglucomutase 1 (Pgm1) on a peripheral residue (Ser63) regulates Pgm1 activity and controls the mobilization of the glycogen stores. Inhibition of Pgm1 activity via phosphorylation on Ser63 appears essential for survival of Synechocystis in the dormant state. Remarkably, this regulatory mechanism seems to be conserved from bacteria to humans. Moreover, phosphorylation of Pgm1 influences the formation of a metabolon, which includes Pgm1, oxidative pentose phosphate cycle protein (OpcA) and glucose-6-phosphate dehydrogenase (G6PDH). Analysis of the steady-state levels of the metabolic products of glycogen degradation together with protein-protein interaction studies revealed that the activity of G6PDH and the formation of this metabolon are under additional redox control, likely to ensure metabolic channeling of glucose-6-phosphate to the required pathways for each developmental stage.

Authors: Sofía Doello, Niels Neumann, Philipp Spät, Boris Maček, Karl Forchhammer

Date Published: 15th Apr 2021

Publication Type: Unpublished

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