GO:0061547 glycogen synthase activity, transferring glucose-1-phosphate

GO:0061547, glycogen synthase activity, transferring glucose-1-phosphate, is a molecular function term that defines the catalytic activity of enzymes transferring glucose-1-phosphate from UDP-glucose to the non-reducing end of an alpha-1,4-glucan chain. This reaction is a key step in the biosynthesis of storage carbohydrates such as glycogen and trehalose, which serve as energy reserves and stress protectants in organisms ranging from bacteria to yeast and humans. The term is distinct from other glycogen synthase activities because it specifically uses UDP-glucose as the donor and releases UMP, rather than UDP or ADP. Understanding this activity is essential for researchers studying carbohydrate metabolism, stress responses, and metabolic disorders. The enzyme responsible for this activity belongs to the glycosyltransferase family and is found in diverse organisms, including Escherichia coli and Saccharomyces cerevisiae. In E. coli, the glucose-1-phosphate adenylyltransferase (EC 2.7.7.27) catalyzes a related step in glycogen biosynthesis, converting glucose-1-phosphate to ADP-glucose, which is then used by glycogen synthase. In S. cerevisiae, trehalose metabolism involves a similar transfer of glucose-1-phosphate during heat shock, highlighting the importance of this activity in stress tolerance. These findings underscore the broad biological significance of GO:0061547. For biomedical researchers, GO:0061547 provides a precise annotation for functional genomics and proteomics studies. It enables the classification of genes and proteins involved in glycogen and trehalose synthesis, and it supports the interpretation of metabolic phenotypes in knockout or overexpression models. As the demand for reproducible, publication-grade data grows, accurate annotation of this activity is critical for comparative genomics, enzyme engineering, and drug target discovery.

GO:0061547 is defined as the catalysis of the reaction: UDP-glucose + (1,4)-alpha-D-glucosyl(n) = UMP + (1,4)-alpha-D-glucosyl(n)-glucose-1-phosphate. In simpler terms, it is a glycosyltransferase activity that transfers a glucose-1-phosphate moiety from UDP-glucose to the end of a growing alpha-1,4-glucan chain, releasing UMP. This activity is involved in the biosynthesis of storage polysaccharides such as glycogen and trehalose.

GO:0061547 is important because it defines a key enzymatic step in the synthesis of storage carbohydrates that are essential for energy homeostasis and stress survival. In bacteria such as Escherichia coli, the related glucose-1-phosphate adenylyltransferase activity is critical for glycogen accumulation, which affects cellular fitness and survival under nutrient limitation. In Saccharomyces cerevisiae, trehalose metabolism, which involves the transfer of glucose-1-phosphate, is rapidly induced during heat shock and other stresses, protecting cells from protein denaturation and osmotic damage. In higher organisms, glycogen synthase activity is central to glucose storage in liver and muscle, and its dysregulation is linked to metabolic disorders. Thus, accurate annotation and study of GO:0061547 are fundamental for understanding carbohydrate metabolism, stress biology, and related diseases.

The following genes and proteins are directly or indirectly involved in glycogen synthase activity transferring glucose-1-phosphate and related storage carbohydrate metabolism.

The activity of glycogen synthase transferring glucose-1-phosphate is regulated at multiple levels. In bacteria, the upstream enzyme glucose-1-phosphate adenylyltransferase is allosterically activated by fructose-1,6-bisphosphate and inhibited by AMP, linking glycogen synthesis to cellular energy status. In Saccharomyces cerevisiae, trehalose metabolism is rapidly induced during heat shock, and the enzymes involved are regulated by phosphorylation and transcriptional activation. In higher organisms, glycogen synthase is inhibited by phosphorylation via GSK3 and activated by dephosphorylation via protein phosphatase 1, integrating hormonal signals such as insulin. These regulatory mechanisms ensure that storage carbohydrate synthesis is tightly coupled to environmental and metabolic cues.

Mutations in genes encoding glycogen synthase and related enzymes can lead to glycogen storage diseases, which are characterized by abnormal glycogen accumulation in tissues such as liver and muscle. Although GO:0061547 specifically describes the transfer of glucose-1-phosphate, defects in this activity or its regulation can contribute to metabolic myopathies and hepatopathies. Research using CRISPR knockout models of GYS1 and GYS2 has helped elucidate the roles of these enzymes in glycogen metabolism and disease.

Dysregulation of glycogen synthase activity is associated with insulin resistance and type 2 diabetes, as impaired glycogen synthesis contributes to hyperglycemia. The activity defined by GO:0061547 is part of the pathway that stores glucose as glycogen, and its modulation by insulin signaling is critical for glucose homeostasis. Studying this activity in cell and animal models can provide insights into the molecular basis of metabolic disorders.

In pathogenic bacteria and fungi, the ability to synthesize storage carbohydrates such as glycogen and trehalose is linked to survival under stress and virulence. For example, in Escherichia coli, glycogen accumulation supports persistence during nutrient limitation. In Saccharomyces cerevisiae, trehalose protects against heat shock and oxidative stress. Targeting the enzymes that catalyze GO:0061547 could therefore be a strategy for antimicrobial development.

Direct measurement of glycogen synthase activity transferring glucose-1-phosphate can be performed using radiolabeled UDP-glucose and a glucan acceptor, followed by precipitation and scintillation counting. This method allows kinetic characterization of the enzyme, including Km and Vmax for substrates. In bacteria, similar assays are used to measure glucose-1-phosphate adenylyltransferase activity.

CRISPR-Cas9 knockout of genes encoding the enzyme or its regulators provides a powerful way to assess the cellular consequences of loss of GO:0061547 activity. Knockdown using siRNA or shRNA can also be used for transient depletion. These approaches have been applied in E. coli and S. cerevisiae to study glycogen and trehalose metabolism.

RNA-seq and proteomics can reveal changes in gene expression and protein abundance upon modulation of glycogen synthase activity. Metabolomics can quantify glycogen, trehalose, and intermediate metabolites, providing a systems-level view of the pathway. These methods are essential for understanding the broader metabolic network linked to GO:0061547.

Fluorescence microscopy of tagged glycogen synthase or trehalose enzymes can reveal their subcellular localization and dynamics. In yeast, GFP-tagged Tps1 has been used to study its distribution during heat shock. In mammalian cells, imaging of glycogen granules can be achieved using specific dyes or tagged proteins.

Researchers studying glycogen synthase activity, transferring glucose-1-phosphate-related genes often need to determine whether a candidate gene is causally involved in storage carbohydrate metabolism, stress response, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of genes annotated to GO:0061547.

GO:0061547, glycogen synthase activity transferring glucose-1-phosphate, is a fundamental molecular function in storage carbohydrate metabolism. Its precise definition and annotation enable researchers to study glycogen and trehalose biosynthesis across organisms, from bacteria to humans. The activity is linked to stress responses, metabolic disorders, and potential therapeutic targets. By leveraging CRISPR-based models and biochemical assays, scientists can continue to uncover the mechanistic details and physiological roles of this important enzyme activity.