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Amino acids contains two functional groups, amino group (-NH2) and carboxyl group (-COOH) in same molecule.

On the basis of relative position of these group in molecule, they are classified as α, β, ϒ etc. amino acids. Out of these amino acids, only α-amino acids involve in the formation of proteins. Total 26 different amino acids are isolated by the hydrolysis of various proteins.

In these 26 amino acids, twenty amino acids occur in almost all proteins and six are found in special proteins only. Those amino acids which have equal number of amino and carboxyl group in molecule are called as neutral amino acids.For example; Glycine, Alanine etc.

However the presence of one additional amino group makes molecule basic and one additional carboxyl group makes molecule acidic in nature. For example; Lysine is a basic amino acid due to the presence of one additional amino group in side chain and glutamic acid is an acidic amino acids because of carboxyl group.

On the basis of their requirement and production, amino acid can be classified as essential and non-essential amino acid. Essential amino acids cannot synthesis by body and must be a part of diet. However non-essential ammonia acid synthesized in human body. Some essential and non-essential amino acids are as follows.

Amino acids
Nonessential Essential
1 Alanine Arginine
2 Asparagine Histidine
3 Aspartate Isoleucine
4 Cysteine Leucine
5 Glutamate Lysine
6 Glutamine Methionine
7 Glycine Phenylalanine
8 Proline Threonine
9 Serine Tyrptophan
10 Tyrosine Valine


What is Glutamine?

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Glutamine or Gln or Q is one of the non-essential amino acid which encoded by CAA and CAG. It becomes conditional essential amino acid in certain situations like intensive athletic training or certain gastrointestinal disorders. It contains one amino group, one carboxyl group with an amide group in side-chain.

  1. The concentration of glutamine in human blood is about 500-900 µmol/L.
  2. Because of the presence of amino and amide group in glutamine molecule, it acts as a primary conductor of nitrogen to the muscles and found in high concentrations in the muscles, lungs, kidney, liver and where it involves in multiple and critical functions.
  3. It is the most abundant amino acid in the body, involve in protein synthesis.
  4. As it is a non-essential amino acid, human body can synthesis this amino acid for regular needs. In case of extreme stress like exercise or an injury body may need more glutamine than the regular dose. In human body, glutamine is generally stored in muscles followed by the lungs as it mainly synthesis there only.
  5. The most important function of glutamine is the removal of excess ammonia which is a waste product in the body.
  6. Glutamine also helps the immune system function and required for normal brain function and digestion. As enough glutamine is synthesized in body only, but during some medical urgency like surgery, infections, and prolonged stress decreases the glutamine level in body which can be recover with the hel of glutamine supplement which are commercially available as powdered form or a piles or as liquid.

Many animal and plant proteins are found high concentration of glutamine amino acid like milk, cottage and ricotta cheese, spinach, parsley and cabbage, beef and pork. Some vegetable juices are containing littlie amount of L-glutamine.

Amino Acid Glutamine

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The amide form of glutamic acid is glutamine, with one amino group and carboxyl group on alpha carbon atom and one amide group on side chain. It is a polar and uncharged molecule which can be synthesized in body, thus a non-essential amino acid.

Compared to asparagine amino acid, glutamine contains an extra single '-CH2' (methylene) group in the side chain which helps glutamine in its free form or as in N-terminus of the proteins to cyclize spontaneously and deamidate, which helps in yielding the six-member ring structure pyrrolidone carboxylic acid in many immunoglobulin polypeptides.

Like other amino acids, it can also form zwitterion with two opposite charges on same molecule, thus show isoelectric point at 5.65. The molecular formula of glutamine is C5H10N2O3 with molecular weight of 146.15 g/mol. The pKa values of carboxyl group and amino group is 2.17, 9.13 respectively and show high solubility in water.
Amino Acid Glutamine

Out of D and L configuration, L-glutamine is more common. It can easily break non-enzymatically into ammonia and pyroglutamate in liquid medium. The cleavage if molecule depends upon the pH, temperature and the presence of various anions. The deamination of glutamine occurs readily in the presence of phosphate or bicarbonate either in acidic or basic medium. The deamination process is ph dependent and occurs at fast speed at pH 4.3 to 10.

Glutamine is generally synthesized inhuman body by glutamate and ammonia in the presence of enzyme glutamine synthetase.
Glutamine Synthetase

  • The maximum amount of glutamine produce in muscular tissues around 90% of all glutamine synthesized. Some of glutamine is also synthesis in lungs, brain and liver.
  • Liver is mainly involved in regulation of glutamine metabolism than producing, as the liver takes up large amounts of glutamine derived from the gut.
  • Like other amino acids, glutamine involves in protein synthesis and also acts as a source for cellular energy.
  • It regulates the acid-base balance in the kidney by producing ammonia in the presence of glutaminase enzyme.

Glutaminase Enzyme

Glutamine also involves in synthesis of purine where it acts as Nitrogen donor and also acts as carbon donor in refilling the citric acid cycle.

Glutamine Benefits

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Human body can synthesis enough amount of glutamine amino acid which further involve in various biochemical process. It is mainly involve metabolic process of kidney and liver. Some benefits of glutamine in different biological process are as follow.

In cell culture systems

  • There are two amino acids, glutamine and glutamate which primary involve in cell culture for the growth of cells.
  • Glutamine acts as an alternative source of energy for dividing cell as these cells cannot use glucose efficiently.
  • During the cell division there is a large demand of nitrogen for the synthesis of nucleic acid, proteins, amino-sugars and vitamins.
  • This demand of nitrogen is satisfied by ammonium ion which initially incorporates into organic nitrogen as an amine of glutamate or an amide of glutamine.
  • Hence these two amino acids act as reservoirs of nitrogen for the synthesis of nitrogen containing bio molecules.

Glutamine also involves in transportation and delivery of nitrogen to cells in quantities which are toxic as free ammonium ion. The amide group of glutamine is used in the production of the vitamins NAD and NADP, CTP from UTP, purine nucleotides and asparagine and carbamyl phosphate which further used in the production of pyrimidine.

Glutamine involves in the synthesis of other amino acids also like glutamate and also used for the trans amination of alpha ketoacids for the synthesis of other alpha amino acids. The overall conversion is as follows.

NH4+ + $\alpha $-ketoglutarate + NADPH + H+ $\rightarrow$ L-glutamate + NADP+ + H2O
Glutamate + NH4+ + ATP $\rightarrow $ glutamine + ADP + Pi + H+
$\alpha $-ketoglutarate + glutamine + NADPH + H+ $\rightarrow $ 2-glutamate + NADP+

Glutamine Benefits
In the presence of two important enzymes, glumate dehydrogenase and glutamine synthetase, both glutamine and glutamic acid involve in the production of other important biological molecules like urea, GABA, amino sugars, nucleotides and polyamines.
  1. Glutamine formed glutamate in brain and promotes the synthesis of GABA which is an important brain neurotransmitter. Glutamine also used to maintain the structural integrity of the intestinal lining and plays a major role in secretion of Human Growth Hormone (HGH) and anti-catabolism, in synthesis of muscle protein an cell-volumizing.
  2. Glutamine also involves in many gastrointestinal function including maintenance of gut barrier function and cell differentiation due to high extraction rate of glutamine in intestine. During the body stress because of several factors like burn, surgery and infections, the cortisol level increases in bloodstream which can lower the bodies stores of glutamine and increase the possibility of death in trauma.
  3. The ingestion of glutamine to enteral nutrition by tube feeding helps in recovery from illness and wound healing. Several glutamine supplements help to provide strength to the immune system and reduce infections which are associated with surgery and also help in the recovery of severe burns.
  4. The internal lining of the gastrointestinal tract is called as the mucosa which may be protecting by glutamine. Hence glutamine is used for the treatment of for inflammatory bowel disease like ulcerative colitis and Crohn' s disease.
  5. Glutamine supplements along with other important nutrients like vitamins C and E, acetyl cysteine helps in weight gain and for the better absorption of nutrients by intestines. Thus these supplements can be helpful for people suffering with HIV or AIDS and experience severe weight loss.
  6. The excess of physical stress like exercise during events like marathons may reduce the level of glutamine in athletic bodies. The low level of glutamine makes them susceptible for normal viral diseases like cough and cold as glutamine plays an important role in immune system. The intake of glutamine supplements can help them to recover at fast speed.
  7. During cancer disease the level of glutamine decreases as it acts as energy source for rapidly dividing cells, thus glutamine supplements may be helpful for conventional cancer treatment for some people and often used during chemotherapy or radiation treatments. This amino acid is also beneficial during the inflammation of the mouth (stomatitis) and diarrhea associated with chemotherapy.
  8. Glutamine is also marketed in the form of supplements which is used for muscle growth in weightlifting, endurance, bodybuilding and other sports. Glutamine can be increase plasma human growth hormone (HGH) levels by stimulating the anterior pituitary gland.
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