Essential amino acids

Amino acids are the building blocks of proteins. There are 20 amino acids that make up all of the known proteins in an organism. Chemically amino acids are composed of amino and carboxyl group attached to same alpha-carbon. Generally speaking, amino acids are involved as an intermediate in body’s various metabolic pathways. They also have various catalytic and hormonal functions.

On the basis of our body’s ability to denovo synthesize amine acids, they are divided into two groups:

·         Essential amino acids

·         Non essential amino acids

The amino acids that cannot be synthesized in our body and we require their dietary intake are termed as Essential amino acids. While those who can be denovo synthesized are Non essential amino acids.

Some amino acids are also termed as semi essential, i.e. they cannot be synthesized in the body of children but can be synthesized in adult human body. So children require their dietary intake while adults don’t. These amino acids are Arginine and Histidine.

Essential amino acids are

·         Arginine*

·         Lysine

·         Histidine*

·         Methionine

·         Isoleucine

·         Threonine

·         Leucine

·         Phenylalanine

·         Valine

·         Tryptophan

Among these the starred ones are semi-essential amino acids.

Deficiency of any of the essential amino acid in our dietary intake can lead to various diseases in our body. Structurally, essential and non essential amino acids cannot be distinguished from each other, the only difference is the ability of our body to synthesize non-essential ones and inability to synthesize essential ones.

Arginine

Arginine is a semi-essential amino acid. That means that children don’t have the ability to synthesize arginine but adults usually can synthesize this amino acid. Arginine improves and strengthens the immune system. Foods that contain arginine include flour, almond, walnuts and dairy products. Arginine is also necessary for production of Nitric oxide in endothelial cells. This nitric oxide act as vasodilator and regulator of blood pressure. Some studies also reveal the effects of Arginine on male libido.

Lysine

Lysine is an essential amino acid which our body cannot synthesize on its own. Lysine is a base that is encoded by AAA and AAG codon. Food sources that contain lysine are meat, soy bean, cheese, fish and eggs. Lysine was previously thought to control herpes simplex virus infection but it has not yet been approved by FDA for this purpose. Lysine increases the ability to absorb calcium and decrease the urinary loss of calcium. It also enhances the production of collagen and other connective tissue components.

Histidine

Histidine is a semi –essential amino acid that has negatively charged Imidiazole functional group. Histidine has a major role in myelin sheath formation that insulates the nerve fibers. Histidine also has a major role in production of red blood cells and white blood cells. Studies also reveal the effect of histidine in Platelet formation and function thus effecting blood clotting and homeostasis. Histidine increases the absorption of calcium and decrease histamine levels in our body. Clinically histidine is used during the treatment of rheumatoid arthritis and duodenal ulcers.

Methionine

Methionine is also an essential amino acid. Methionine is encoded by AUG codon. It is a sulphur containing amino acids that act as an intermediate in synthesis of cystein, lectin and phospholipids. Food sources of methionine are Brazil nuts, fish and meat. Major function of methionine is its role as an antioxidant. Its deficiency thus leads to oxidative stress in our body.

Isoleucine

Isoleucine is another essential amino acid that has a branched hydrocarbon chain. Foods that contain this amino acid include eggs, sea weed, chick, lamb and fish. Isoleucine promotes tissue repair and prevent muscle wasting. This amino acid can be converted to sugar in liver.

Threonine

Threonine is an alpha amino acid that is encoded by ACU, ACA, ACC, ACG. Food sources that contain threonine include Cheese, lentils, sesame seeds, meat and fish. Threonine is necessary for biosynthesis of glycine and serine which are needed for connective tissue formation. Threonine improves tissue repair. This amino acid also improves immune system by helping in the biosynthesis of antibodies.

Leucine

Leucine is an essential amino acid that is encoded by UUA, UUG, CUU, CUC, CUA and CUG codons. Leucine is found in various foods that include soy bean, beef, oat and corn. Leucine helps in regulation of blood glucose levels and takes part in tissue repair. Leucine helps in muscle mass building.

Phenylalanine

Phenylalanine is a non polar essential amino acid that is converted to L-tyrosine. L-tyrosine is used in dopamine, norepinephrine and epinephrine biosynthesis. Clinically phenylalanine is used for the treatment of Vitiligo along with UVA exposure. It has also antidepressive action.

Valine

Valine is another essential amino acid that is encoded by GUU, GUC, GUA and GUG. Valine is needed for muscle metabolism and helps maintain nitrogen balance in our body. Valine improves tissue repair, prevents muscle loss and improves muscle coordination.

Tryptophan

Tryptophan is an essential amino acid that is encoded by UGG codon. Food sources that contain this amino acid are Chocolate, peanuts, banana, egg, fish and cheese. Tryptophan has a role in production in Vit B complex (niacin). Tryptophan also acts as an intermediate in serotonin synthesis.

Deficiencies

Deficiency of any of the above mentioned amino acid can lead to several abnormalities in our body’s function that extends from generalized weakness to brain and cardiovascular malfunctions. A balanced and healthy diet should include all of these essential amino acids in required quantities. The amino acids are now also available in form of medications.