| IUPAC name
| Other names
|3D model (Jmol)||Interactive image|
|Molar mass||146.15 g·mol−1|
|Melting point||decomposes around 185°C|
|Acidity (pKa)||2.2 (carboxyl), 9.1 (amino)|
Chiral rotation ([α]D)
|+6.5º (H2O, c = 2)|
|Supplementary data page|
| Refractive index (n),|
Dielectric constant (εr), etc.
| Phase behaviour|
|UV, IR, NMR, MS|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|(what is ?)|
Glutamine (abbreviated as Gln or Q; encoded by the codons CAA and CAG) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −COO− form under biological conditions), and a side chain amide which replaces the side chain hydroxyl of glutamic acid with an amine functional group, classifying it as a charge neutral, polar (at physiological pH) amino acid. It is non-essential and conditionally essential in humans, meaning the body can usually synthesize sufficient amounts of it, but in some instances of stress, the body's demand for glutamine increases and glutamine must be obtained from the diet.
In human blood, glutamine is the most abundant free amino acid, with a concentration of about 500–900 µM.
Glutamine plays a role in a variety of biochemical functions:
- Protein synthesis, as any other of the 20 proteinogenic amino acids
- Lipid synthesis, especially by cancer cells.
- Regulation of acid-base balance in the kidney by producing ammonium
- Cellular energy, as a source, next to glucose
- Nitrogen donation for many anabolic processes, including the synthesis of purines
- Carbon donation, as a source, refilling the citric acid cycle
- Nontoxic transporter of ammonia in the blood circulation
- Precursor to the neurotransmitter glutamate
Producing and consuming organs
Glutamine is synthesized by the enzyme glutamine synthetase from glutamate and ammonia. The most relevant glutamine-producing tissue is the muscle mass, accounting for about 90% of all glutamine synthesized. Glutamine is also released, in small amounts, by the lung and the brain. Although the liver is capable of relevant glutamine synthesis, its role in glutamine metabolism is more regulatory than producing, since the liver takes up large amounts of glutamine derived from the gut.
The most eager consumers of glutamine are the cells of intestines, the kidney cells for the acid-base balance, activated immune cells, and many cancer cells.
Glutamine oral supplementation significantly reduces the risk of systemic infections originating from the gut such as in critically ill individuals and in individuals who have had abdominal surgery. The reduction in rates of infections in these groups of people are due to glutamine improving intestinal barrier function including reducing increased intestinal permeability. Intravenous administration does not appear to produce these benefits, however.
Occurrences in nature
Glutamine is the most abundant naturally occurring, nonessential amino acid in the human body, and one of the few amino acids that can directly cross the blood–brain barrier. In the body, it is found circulating in the blood, as well as stored in the skeletal muscles. It becomes conditionally essential (requiring intake from food or supplements) in states of illness or injury.
Dietary sources of L-glutamine include beef, pork, chicken, fish, eggs, milk, dairy products, wheat, cabbage, beets, beans, spinach, and parsley. Small amounts of free L-glutamine are also found in vegetable juices.
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