[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Glutamine synthetase

[Biochemistry](https://durgical.com/en/biochemistry/) · Enzyme

# Glutamine synthetase

Glutamine synthetase traps free ammonia by joining it to glutamate. This protects the brain and carries nitrogen safely in the blood.

Updated 2026-11-01

Loading the 3D model…

## Key facts

- Glutamate + NH₄⁺ + ATP → glutamine + ADP + Pi.
- In the brain it sits in astrocytes and is the main route for removing ammonia.
- In the liver it sits in hepatocytes around the central vein: it traps ammonia that escaped the urea cycle.
- It is a decamer: two rings of five subunits with the active sites between them.

**EC number**
[6.3.1.2](https://www.enzyme-database.org/query.php?ec=6.3.1.2)

**Genes**
GLUL

**Structure (PDB)**
[2QC8](https://www.rcsb.org/structure/2QC8)

## Structure

- 2QC8: human glutamine synthetase with ADP and methionine sulfoximine phosphate, an inhibitor that mimics the intermediate.

## Regulation

- Glucocorticoids induce it; excess glutamine speeds its breakdown.

## Inhibitors and toxins

- Methionine sulfoximine (experimental)
- Glufosinate (herbicide)

## Clinical notes

- In hyperammonaemia, astrocytes pile up glutamine, swell, and cerebral oedema follows.
- Its very rare congenital deficiency leaves glutamine almost undetectable and causes severe brain damage.

## Related conditions

- [Hyperammonaemia](https://durgical.com/en/conditions/hyperammonaemia/)
- [Cirrhosis](https://durgical.com/en/conditions/cirrhosis/)

## Related

- [Glutamine](https://durgical.com/en/biochemistry/molecules/glutamine/)
- [Glutamate (glutamic acid)](https://durgical.com/en/biochemistry/molecules/glutamate/)
- [Ammonia (ammonium)](https://durgical.com/en/biochemistry/molecules/ammonia/)
- [Transamination and deamination](https://durgical.com/en/biochemistry/topics/transamination-and-deamination/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which brain cells clear ammonia with glutamine synthetase?

Astrocytes; that is why they swell when ammonia rises.

## What is its job in the liver if the urea cycle already exists?

Perivenous cells trap as glutamine the ammonia that was not turned into urea in the periportal zone.

## How much energy does the reaction cost?

One ATP per glutamine made.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/biochemistry/enzymes/glutamine-synthetase/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [GLUL: Glutamine synthetase (human)](https://www.uniprot.org/uniprotkb/P15104/entry) (UniProt, 2026); [Glutamate and glutamine metabolism](https://reactome.org/PathwayBrowser/#/R-HSA-8964539) (Reactome, 2026); [2QC8: Crystal structure of human glutamine synthetase in complex with ADP and methionine sulfoximine phosphate](https://www.rcsb.org/structure/2QC8) (RCSB Protein Data Bank, 2026).

[← All of biochemistry](https://durgical.com/en/biochemistry/)

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/biochemistry/enzymes/glutamine-synthetase/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/enzymes/glutamine-synthetase/