Summary
Glutamine (symbol Gln or Q) is an α-amino acid that is used in the biosynthesis of proteins. Its side chain is similar to that of glutamic acid, except the carboxylic acid group is replaced by an amide. It is classified as a charge-neutral, polar 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. It is encoded by the codons CAA and CAG. In human blood, glutamine is the most abundant free amino acid. The dietary sources of glutamine include especially the protein-rich foods like beef, chicken, fish, dairy products, eggs, vegetables like beans, beets, cabbage, spinach, carrots, parsley, vegetable juices and also in wheat, papaya, Brussels sprouts, celery, kale and fermented foods like miso. 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. Integrity of healthy intestinal mucosa, though small randomized trials have shown no benefit in Crohn’s disease. Cancer cells rely on glutamine metabolism as carbon and nitrogen sources. Glutamine level in the blood serum is the highest among other amino acids and is essential for many cellular functions. Studies have indicated the importance of glutamine in certain tumors. For example, the inhibition of glutamine metabolism was reported to prevent growth of several tumors such as breast, liver, kidney and T-cell lymphoblastic leukemia. Glutamine maintains redox balance by participating in glutathione synthesis and contributing to anabolic processes such as lipid synthesis by reductive carboxylation.
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Related concepts (17)
Nutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures, such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted to smaller molecules in the process of releasing energy, such as for carbohydrates, lipids, proteins, and fermentation products (ethanol or vinegar), leading to end-products of water and carbon dioxide.
Essential amino acid
An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms, the nine amino acids humans cannot synthesize are valine, isoleucine, leucine, methionine, phenylalanine, tryptophan, threonine, histidine, and lysine.
Biosynthesis
In molecular biology, biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles.
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