During intense training or serious illness, your body quickly runs out of the amino acids it normally keeps in reserve. One of these is glutamine, stored mostly in your muscles and released when needed. Even immune cells and the gut depend on it when under stress.
In this study guide, you’ll learn what glutamine is, how it moves between the gut, liver, and muscle, and why your body increases its demand in catabolic conditions. We’ll also cover glutamine metabolism, dietary sources, safety data, and the enzymes that control its levels in different organs.
Glutamine: Quick Summary
Do you just need the basics? Here’s a simple explanation of what glutamine is and how it works:
🟠 Glutamine is a neutral, polar amino acid with an amide group, formed in cells from glutamate and ammonia using ATP.
🟠 It supports energy metabolism by supplying carbon and nitrogen for ATP production, nucleotide synthesis, and the Krebs cycle.
🟠 During infections or physical stress, immune cells like lymphocytes and macrophages rely on glutamine for growth and function.
🟠 The gut uses large amounts of glutamine for energy and to maintain intestinal lining and barrier function.
🟠 Skeletal muscle stores most of the body’s glutamine and produces it through glutamine synthetase, especially during fasting or illness.
🟠 The liver converts glutamine into urea and glutamate, helping control blood pH and nitrogen removal.
🟠 You can get glutamine from protein-rich foods like meat, dairy, spinach, and fermented products, or through L-glutamine supplements.
🟠 Glutamine is safe at standard doses, though supplementation isn’t recommended for people with severe liver disease unless monitored.
What Is Glutamine?
Glutamine is an amino acid that your body uses to build proteins. It has five carbon atoms and a side chain with an amide group, which makes it polar but without a charge. This side chain sets it apart from glutamic acid, which has a carboxyl group instead. Both have similar backbones, but the change in the side chain gives them different properties.
Your body makes glutamine by combining glutamate with ammonia using the enzyme glutamine synthetase. This reaction uses energy from ATP. Most glutamine is formed in your muscles and then travels to other tissues through the blood. It’s one of the amino acids your body can produce, but in some conditions, you may need more from food.
Properties of glutamine
- Neutral
- Polar
- Proteinogenic (used in protein synthesis)
- Made from glutamate and ammonia
- Found in muscle and blood in high amounts
Chemical and physical data
| Property | Value |
| Molecular formula | C₅H₁₀N₂O₃ |
| Molar mass | 146.15 g/mol |
| Solubility in water | Soluble |
| Plasma concentration | 500–800 µmol/L (fasting) |
| Zwitterion at pH 7 | Yes |
Glutamine Supports Metabolism and Energy Production
Your cells use glutamine to produce energy and build other molecules. Inside the cell, glutamine turns into glutamate, then into α-ketoglutarate. This molecule enters the Krebs cycle, where it supports ATP production. The energy made through this cycle helps fuel active cells.
Glutamine also provides carbon and nitrogen atoms. These are needed to form DNA, RNA, and amino sugars. This makes glutamine important during growth, repair, and high metabolic activity. Cells in your intestines, kidneys, and brain rely on glutamine when glucose is limited.
Metabolic processes involving glutamine
- ATP production in the Krebs cycle
- Nucleotide formation (purines and pyrimidines)
- Glutathione synthesis for redox balance
- NADPH generation
- Production of amino sugars
Glutamine Feeds the Immune System During Stress
During infections, trauma, or intense exercise, your immune cells need extra glutamine. Lymphocytes use it to divide and send signals. Macrophages and neutrophils need it to destroy bacteria and remove damaged cells. These cells rely on glutamine as a fuel source and for making proteins.
When you’re sick or recovering, your muscles release stored glutamine into the blood. If levels drop too far, immune cells slow down. This weakens the defense against bacteria and viruses. That’s why hospitals often include glutamine in nutrition plans for patients after surgery or injury.
Even though glucose gives energy, immune cells often use more glutamine than glucose during stress. This makes glutamine one of the most used amino acids in active immune responses.
When immune cells need glutamine most
- During infections or sepsis
- After surgery or physical trauma
- After high-intensity training
- In malnutrition or long recovery periods
The Gut Actively Breaks Down Glutamine for Energy
Cells in your intestines rely on glutamine for energy. They prefer it over glucose. Enterocytes absorb glutamine and use the enzyme glutaminase (GLS) to convert it into glutamate and ammonia. Glutamate then turns into α-ketoglutarate, which enters the Krebs cycle and supports ATP production.
This energy keeps the gut lining strong and active. During fasting or illness, GLS activity increases. The gut breaks down more glutamine to keep working. Unlike other tissues, the gut doesn’t store glutamine—it uses it immediately. If intake is low, it draws from blood levels.
Low glutamine in the gut can weaken the lining and raise the risk of bacterial entry into the bloodstream. This becomes a bigger problem during stress or malnutrition. Gut cells also use glutamine to make other amino acids, helping with protein repair and barrier function.
Skeletal Muscle Stores and Synthesizes Most Glutamine
Your skeletal muscles hold the largest glutamine reserve. Muscle cells make glutamine from glutamate, ammonia, and ATP using the enzyme glutamine synthetase.
Glutamate + NH₄⁺ + ATP → Glutamine + ADP + Pi
This reaction stores nitrogen safely and supports other organs. Insulin and growth hormone boost glutamine production. Glucocorticoids increase their release into the blood. Muscle fibers differ, too. Slow-twitch fibers make and store more glutamine than fast-twitch fibers due to higher glutamine synthetase activity.
How muscles produce glutamine in fasting
When you fast, your muscle breaks down protein. Some amino acids convert to glutamate. This glutamate reacts with ammonia to form glutamine. That glutamine moves into the bloodstream to fuel cells in the gut, liver, and immune system.
What happens during illness or inflammation
Infections and injuries raise glutamine demand. Muscles respond by speeding up production. But if stress continues, glutamine levels fall. This leads to muscle loss. Inflammation increases glucocorticoid levels, which signal the muscle to release more glutamine. This response helps other organs cope, but it reduces muscle strength over time.
The Liver Converts Glutamine and Controls Blood pH
During stress, your liver uses glutamine to remove nitrogen waste and manage blood pH. Glutamine enters liver cells and breaks down into glutamate and ammonia. Ammonia then joins the urea cycle. This process forms urea, which the body removes through urine. Urea production keeps ammonia from building up and helps stabilize blood pH.
Glutamine breakdown happens in specific liver zones. Periportal hepatocytes use glutamine to generate urea. Perivenous hepatocytes recycle leftover ammonia back into glutamine. These zones work together to remove excess nitrogen and prevent tissue damage.
Periportal vs perivenous glutamine function
Periportal cells take up glutamine and remove nitrogen by forming urea. Perivenous cells act as a backup, converting extra ammonia into glutamine. This keeps nitrogen levels stable throughout the liver.
Glutamine in liver swelling, fibrosis, and glucose regulation
Liver cells swell when they take in glutamine. This triggers glycogen and fat production and reduces protein breakdown. In liver fibrosis, some cells use glutamine to make collagen. Too much glutamine may worsen scarring in damaged livers.
Dietary Sources of Glutamine in Food
Your body makes glutamine, but diet can help during stress or illness. High-protein foods are the main source. After digestion, glutamine supports muscle stores and tissue repair.
Examples of glutamine-rich foods:
- Beef, chicken, and fish
- Milk, cheese, and eggs
- Spinach, cabbage, and beets
- Beans, lentils, and parsley
- Miso, sauerkraut, and other fermented foods
Dietary glutamine supports normal metabolism when your body needs more than it can produce.
How the Brain Uses Glutamine in Neurotransmitter Cycling
Brain cells rely on glutamine to maintain neurotransmitter levels. Neurons release glutamate as a signal molecule. After firing, astrocytes absorb the leftover glutamate and convert it into glutamine using glutamine synthetase. This glutamine then returns to neurons, where it turns back into glutamate for reuse. This constant cycling keeps neural communication steady.
Glutamine also acts as a buffer for ammonia in the brain. Ammonia is toxic to nerve cells, but glutamine formation safely traps it. During liver disease or metabolic disorders, this process can go into overdrive, leading to brain swelling or confusion. In these cases, glutamine levels in the brain rise, even if blood levels drop.
This glutamate–glutamine cycle is especially active in the cerebral cortex, which controls memory and awareness. Without it, nerve cells lose the ability to fire properly. That’s why even small changes in glutamine metabolism can affect mood, thinking, or coordination.
Glutamine Supplementation in Recovery and Clinical Nutrition
During illness or injury, your body breaks down more protein and uses more glutamine. If food intake drops or the body can’t keep up, doctors may add glutamine to medical nutrition. It’s often given as L-glutamine powder or included in feeding formulas for recovery.
Supplementation in illness and trauma
After surgery, burns, or sepsis, muscle glutamine stores shrink. Hospitals use glutamine-enriched formulas to support gut cells and help immune cells multiply. This is common in intensive care, especially when the digestive tract is affected.
Supplementation in sports recovery
After long or intense training, glutamine levels can drop. Some athletes use supplements during recovery to maintain immune balance. Glutamine may also reduce the risk of infection during repeated high-volume training periods.
Safety of Glutamine and Side Effects
Glutamine is safe when taken at doses up to 14 grams per day. Most healthy people tolerate it well. Side effects are rare but can include stomach pain or bloating. People with liver disease, kidney failure, or certain cancers should avoid supplements unless advised by a doctor.
Get Help from a Chemistry Tutor to Master Glutamine Metabolism
Struggling to follow how glutamine moves between tissues or supports immune cells? You’re not alone. This topic ties together biochemistry, physiology, and molecular metabolism—areas that often confuse students. A one-on-one biochemistry tutor can walk you through glutamine’s synthesis, its breakdown via glutaminase, and its role in energy and nitrogen balance. If you’re revising for exams or writing assignments, private chemistry tutoring helps you spot connections that textbooks don’t always explain clearly.
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Glutamine: Frequently Asked Questions
1. What is the structure of glutamine?
Glutamine has a five-carbon backbone with an amino group on the α-carbon and an amide group on the side chain.
2. Is glutamine the same as glutamic acid?
No, glutamine has an amide group, while glutamic acid has a carboxylic acid group on the side chain.
3. How is glutamine synthesized in the body?
Glutamine forms from glutamate and ammonia through the enzyme glutamine synthetase.
4. What organs store the most glutamine?
Skeletal muscle stores most of the body’s glutamine.
5. Can glutamine cross the blood–brain barrier?
Yes, glutamine is one of the few amino acids that crosses the blood-brain barrier easily.
6. What is the plasma concentration of glutamine?
Plasma glutamine levels range from 500 to 800 µmol/L in healthy individuals.
7. When do glutamine levels drop?
Levels drop during trauma, illness, sepsis, and intense physical activity.
8. Is glutamine safe for daily supplementation?
Yes, doses up to 14 grams per day are safe for healthy people.
Sources:
1. NCBI
2. Britannica
3. Wikipedia
