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Tryptophan

Amino acids are found in our bodies and act as building blocks of the proteins. On the basis of the position of functional groups present in amino acids (amino group and carboxyl group), they can be various types, alpha, beta, gamma amino acids and so on. Only twenty alpha amino acids involve in the formation of proteins. Out of these twenty amino acids, ten amino acids can be synthesized in human body and known as non-essential amino acids.

Rest of the ten amino acids cannot synthesized in human body, hence they must be taken by diet as deficiency of these amino acids can be responsible for several diseases and called as essential amino acids. The high protein foods provide these essential as well as non-essential proteins to human body. Some common examples of such food are beans, pluses, nuts, eggs, dairy products and meat.

Apart from protein diets, there are many commercial protein supplements are available which help to combat depression and anxiety and ensure the proper nourishment of body. Amino acids play an important role in metabolism and in nutrition. They involve in condensation polymerization to form polymeric chains known as peptides which further polymerized to form longer chains called as polypeptides or proteins. Proteins act as a structural unit for human body and also involve in system functions. Proteins help to support muscle recovery, hair and nail growth and in bone and tissue reproduction.

 

What is Tryptophan?

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Tryptophan is an aromatic, non-polar and essential amino acid with molecular formula C11H12N2O2 and molecular mass 204.23 g mol−1. It is also abbreviated as Trp or W and marketed as Tryptan. UGG is the genetic codon for this amino acid. Tryptophan was first isolated from hydrolysis of casein by Frederick Hopkins in 1901.

Tryptophan is easily soluble on water and solubility increases with increasing the temperature. It is also soluble in hot alcohol and alkali hydroxide but insoluble in non-polar solvents like chloroform. Tryptophan considered as a derivative of Alanine, which has an indole substituent at β-carbon atom of side chain, can be identifying by ultra-violet spectrum. The indole nitrogen of tryptophan can involves in hydrogen bond formation with solvent molecule and gets folded in solvent.

Just like other amino acids, tryptophan also shows D and L- configuration and L-stereoisomer of tryptophan is generally present in structural or enzyme proteins, while D-stereoisomer is occasionally found in naturally produced peptides like in marine venom peptide contryphan.

Tryptophan


Chorismate which is an important intermediate for many biosynthetic pathways acts as precursor for biosynthesis of the aromatic amino acids like tryptophan, phenylalanine and tyrosine. Chorismate synthesized by Phosphoenol pyruvate and erythrose 4-phosphate with one NADPH + H+ and one ATP with the formation of 3-Deoxy-D-arabino-heptulosonate-7-phosphate as an intermediate.

This Chorismate involve in a five steps reaction to synthesis tryptophan.
  1. In first step, glutamate provides one amine group to chorismate and pyruvate is lost from chorismate.
  2. Than a ribose sugar is added which eventually contributes to the 5 membered ring of tryptophan in next three steps.
  3. Hydrolysis of pyrophosphate provides energy to the process and helps drive the addition of the ribose sugar in the second step of the reaction.
  4. In the last step serine acts as the donor of the a- carbon amino group of tryptophan.
Chorismate

There are many important side reactions occur during the catabolism and metabolism of tryptophan. This amino acid acts as precursor for many other amino acids and biochemical compounds. For example, Serotonin which is a a neurotransmitter is synthesized in the presence of tryptophan hydroxylase enzyme.

Serotonin further converted into melatonin (neurohormone) in the presence of N-acetyltransferase and 5-hydroxyindole-O-methyltransferase. Other compounds like Niacin can also be synthesized from tryptophan through kynurenine and quinolinic acids as intermediates. Tryptophan can also be converted to Auxin which is a phytohormone.
Serotonin

To take diets which contain tryptophan. There are many natural and synthetic food sources are available which are rich in tryptophan like Pumpkin Seeds which contain around 0.576 grams of tryptophan content per 100 grams of dried pumpkin seeds, eggs, which have 0.167 grams of tryptophan in every 100 grams and meat like turkey. Some other common food sources of tryptophan amino acid are as follow.


Food Sources of Tryptophan Amino Acid

The deficiency of tryptophan may cause the characteristic symptoms of protein deficiency like anxiety, depression and low mood, weight loss, impaired growth in infants and children and insomnia. The requirement of tryptophan varies according to age,, gender as well as with some other
conditions.
Requirement of Tryptophan

Tryptophan Structure

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Tryptophan is an aromatic amino acid which composed of amino group, carboxyl group with one five-membered ring with a nitrogen atom bonded to a benzene ring called as indole ring present in side chain of molecule. The presence of indole ring imparts many specific properties to molecule and tryptophan shows hydrophilic nature. It is a non-polar molecule which form a neutral zwitterion with pKa1 2.83 (α-carboxyl group) and pKa2 9.39 (α-ammonium ion), hence show isoelectric point at 5.89.
Tryptophan Structure

Tryptophan can also exists in D and L form, out of that L- form is generally being a part of most of proteins and D- form is less available.

D and L Configuration

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