Glutamine Synthetase Protein

Glutamine Synthetase Protein

Introduction

Glutamine Synthetase Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-protein"> [@albrecht2019]

| Attribute | Value | [@su2021]
|-----------|-------| [@zou2022]
| Protein Name | Glutamine Synthetase |
| Gene Symbol | GLUL |
| UniProt ID | P15104 |
| PDB Structures | 2OJC, 2QCM, 1F52, 1GQ5 |
| Molecular Weight | 49.2 kDa (monomer), ~492 kDa (decamer) |
| Subcellular Localization | Cytosol |
| Protein Family | Glutamine synthetase family |

</div>}

Overview

Glutamine Synthetase (GS) is a crucial enzyme in nitrogen metabolism that catalyzes the ATP-dependent synthesis of glutamine from glutamate and ammonia.^[1] In the brain, GS is primarily expressed in [astrocytes](/entities/astrocytes) and plays essential roles in the glutamate-glutamine cycle, ammonia detoxification, and neuroprotection. It is implicated in various neurodegenerative diseases including Alzheimer's and Parkinson's disease.

Structure

Quaternary Structure

Glutamine Synthetase Protein

Introduction

Glutamine Synthetase Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.

<div class="infobox infobox-protein"> [@albrecht2019]

| Attribute | Value | [@su2021]
|-----------|-------| [@zou2022]
| Protein Name | Glutamine Synthetase |
| Gene Symbol | GLUL |
| UniProt ID | P15104 |
| PDB Structures | 2OJC, 2QCM, 1F52, 1GQ5 |
| Molecular Weight | 49.2 kDa (monomer), ~492 kDa (decamer) |
| Subcellular Localization | Cytosol |
| Protein Family | Glutamine synthetase family |

</div>}

Overview

Glutamine Synthetase (GS) is a crucial enzyme in nitrogen metabolism that catalyzes the ATP-dependent synthesis of glutamine from glutamate and ammonia.^[1] In the brain, GS is primarily expressed in [astrocytes](/entities/astrocytes) and plays essential roles in the glutamate-glutamine cycle, ammonia detoxification, and neuroprotection. It is implicated in various neurodegenerative diseases including Alzheimer's and Parkinson's disease.

Structure

Quaternary Structure

• Monomer: 373 amino acids (cytosolic form)
• Oligomer: Decamer (10 subunits) arranged in two pentameric rings
• Molecular weight: ~492 kDa for decamer

Active Site

• Catalytic mechanism: ATP-dependent ligation
• Key residues: Asp50, Asp56, Lys263, Cys269
• Metal ion requirement: Mg2+ or Mn2+

Isoforms

| Isoform | Expression | Notes |
|---------|------------|-------|
| GS1 (GLUL) | Brain, liver | Cytosolic |
| GLUL | Eye lens | Lens-specific |

PDB Structures

| PDB ID | Description | Resolution |
|--------|-------------|------------|
| 2OJC | Bacterial GS | 2.0 Å |
| 1F52 | Mammalian GS | 2.2 Å |
| 2QCM | Complex with ADP | 2.1 Å |

Normal Function

Catalytic Activity

GS catalyzes the formation of glutamine:^[2]

Reaction:
Glutamate + NH3 + ATP → Glutamine + ADP + Pi

Steps:

Brain-Specific Roles

• Takes up synaptic glutamate via EAAT transporters
• Converts glutamate to glutamine
• Glutamine shuttled back to neurons
• [Neurons](/entities/neurons) convert glutamine to glutamate

• Captures toxic ammonia in brain
• Converts to non-toxic glutamine
• Essential for hepatic encephalopathy prevention

• Antioxidant properties (glutathione precursor)
• Reduces excitotoxicity
• Maintains redox balance

Role in Disease

Alzheimer's Disease

• Reduced GS: Significant decrease in AD brains
• Impaired glutamate cycling: Contributes to excitotoxicity
• Astroglial pathology: GS+ astrocytes lost in AD

Parkinson's Disease

• Dopaminergic neuron vulnerability: Related to GS deficiency
• Astrocyte dysfunction: Altered glutamine metabolism

Other Conditions

| Condition | GS Role |
|-----------|---------|
| Stroke | Decreased after ischemia |
| Trauma | Biomarker for brain injury |
| Hepatic encephalopathy | Impaired ammonia detoxification |
| ALS | Motor neuron vulnerability |

Therapeutic Implications

| Strategy | Approach |
|----------|----------|
| Gene therapy | AAV-GLUL to astrocytes |
| Metabolic support | Enhance glutamine metabolism |
| Neuroprotection | Reduce excitotoxicity |

Key Publications

Background

The study of Glutamine Synthetase Protein has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

References

[@rose2019]: Rose CF, et al. "Glutamine synthetase in brain: regional distribution and regulation." Adv Neurobiol. 2019;23:299-322. PMID: 31647801(https://pubmed.ncbi.nlm.nih.gov/31647801/)
[@albrecht2019]: Albrecht J, et al. "Glutamine synthetase: A key enzyme in ammonia detoxification." Metab Brain Dis. 2019;34(3):797-805. PMID: 30968334(https://pubmed.ncbi.nlm.nih.gov/30968334/)
[@su2021]: Su Y, et al. "Glutamine synthetase deficiency in Alzheimer's disease." Neurobiol Aging. 2021;105:92-104. PMID: 34092254(https://pubmed.ncbi.nlm.nih.gov/34092254/)
[@zou2022]: Zou J, et al. "Targeting glutamine synthetase for neuroprotection." Neuropharmacology. 2022;210:109059. PMID: 35283142(https://pubmed.ncbi.nlm.nih.gov/35283142/)

See Also

• [Glutamine Synthetase](/proteins/glutamine-synthetase)
• [Glutamate](/mechanisms/glutamatergic-signaling)
• Glutamine-Glutamate Cycle
• [Astrocytes](/cell-types/astrocytes)
• [Alzheimer's Disease](/diseases/alzheimers-disease)

External Links

• [UniProt: P15104](https://www.uniprot.org/uniprotkb/P15104)
• [PDB: 1F52](https://www.rcsb.org/structure/1F52)
• [AlphaFold: P15104](https://alphafold.ebi.ac.uk/entry/P15104)
• [Enzyme Commission: 6.3.1.2](https://www.qmul.ac.uk/sbcs/iubmb/enzyme/6.3.1.2.html)