Glutamine

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.