The ABCs of Cyanobacterial Glycogen: In Vitro Modelling of Glycogen Synthesis and Functional Divergence of Glycogen Synthases in Synechocystis sp. PCC 6803
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Summary Glycogen is the principal carbon reserve in Synechocystis sp. PCC 6803. We reconstituted its biosynthetic pathway in vitro—GlgC (Glucose-1-phosphate adenylyltransferase), two glycogen synthase isoenzymes (GlgA1, GlgA2) and the branching enzyme GlgB—to define how supply, polymerisation and branching set flux and product structure. GlgA2 shows higher specific activity and cooperates with GlgB-generated branched primers, whereas GlgA1 has higher substrate affinity and responds more to primer concentration. Direct coupling of GlgC to GlgA establishes substrate-driven linear flux in which apparent affinity is set upstream by GlgC but the rate is limited at GlgA; increasing the GlgA : GlgC ratio relieves this bottleneck. Regulation of GlgC by 3-phosphoglycerate (activator) and inorganic phosphate (inhibitor), together with differential inhibition of GlgA, further gates flux. Product profiling links mechanism to architecture: GlgA1 produces more-branched glycogen, while GlgA2 yields longer, less-branched polymers, with GlgB biasing utilisation towards GlgA2. These findings support a two-tier control scheme—GlgC gating ADP-glucose supply and GlgA constraining utilisation—modulated by primer context and branching. The complementary behaviours of GlgA1 and GlgA2 provide capacity for rapid accumulation versus steady-state maintenance and offer dynamic metabolic levers to tune glycogen content and architecture in cyanobacteria.
SEEK ID: https://fairdomhub.org/studies/1417
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Projects: SCyCode The Autotrophy-Heterotrophy Switch in Cyanobacteria: Coherent De...
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Created: 6th Nov 2025 at 14:47
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The Deutsche Forschungsgemeinschaft (DFG) is the self-governing organisation for science and research in Germany. It serves all branches of science and the humanities. In organisational terms, the DFG is an association under private law. Its membership consists of German research universities, non-university research institutions, scientific associations and the Academies of Science and the Humanities.
Web page: https://www.dfg.de/en/index.jsp
Cyanobacteria are the only prokaryotes performing oxygenic photosynthesis. Theyhad and have tremendous influence on the biogeochemical cycles on Earth. Recently,cyanobacteria are increasingly investigated as cell factories for a sustainableeconomy. Despite their global, environmental and rising economic importance, ourknowledge on the regulation of their primary metabolism is fragmented.Cyanobacteria switch between photoautotrophic and heterotrophic modes ofmetabolism during day/night cycles or ...
Programme: DFG founded projects
Public web page: https://gepris.dfg.de/gepris/projekt/397695561
Start date: 1st Sep 2018
You will find the following here:
Data summary for all assays in the study
Graphpad Prism file for all figures + analyses
Model.CAB - Glycogen synthesis mathematical model (see README file)
Submitter: Kenric Lee
Assay type: Experimental Assay Type
Technology type: Technology Type
Investigation: 1 hidden item
Model CAB — README
Overview. Model CAB captures the coupled GlgC → GlgA (+ GlgB primer assistance) system under 3‑PGA/Pi regulation. The model exposes GlgC supply, GlgA demand, and a primer effectiveness term from GlgB; it also provides a Pi response calibrated to 2 mM 3‑PGA and helper utilities for GlgA1/GlgA2.
Key parameters (assay context) • GlgA ceilings (Assay B): GlgA1 = 0.49 U·mg⁻¹; GlgA2 = 0.64 U·mg⁻¹. • GlgA Michaelis constants (Assay A; ADP‑Glc): GlgA1 Kₘ = 0.152 mM; GlgA2 Kₘ = 0.219 ...
Creator: Kenric Lee
Submitter: Kenric Lee
Creator: Kenric Lee
Submitter: Kenric Lee
Use to generate all figures and perform analyses.
Get Graphpad here : https://www.graphpad.com/
Creator: Kenric Lee
Submitter: Kenric Lee
