Tryptophan essential amino acid

TR-XRF totally reflecting X-ray fluorescence spectrometry (see TXRF) tryptophan essential amino acid, which participates in the biosynthesis of NAD (nicotinamide adenine dinucleotide) and is the initial precursor of the neurotransmitter serotonin... 

Tryptophan Essential amino acid Insomnia, depression Eosinophilia-myalgia syndrome was reported in 1989, possibly due to contaminants in production of tryptophan. Similar contaminants have been found in 5-hydroxy-l-tryptophan. 

Although corn contains about 10% protein, half of the protein consists of zein, which is especially poor in lysine and tryptophan, essential amino acids which people must get from food (seeTable C-22). 

Tryptophan Essential amino acid that possesses two aromatic rings in its structure. After lysine, tryptophan is considered the most limiting amino acid in maize. Tryptophan can be converted to the B-vitamin niacin in the body. 

C11H12N2O2. M.p. 289°C. L-Tryptophan is an essential amino-acid, its presence in the food of animals is necessary for proper growth. It is present in small quantities in the hydrolysis products of most proteins, although absent in certain vegetable proteins. 

Because of the simplicity of swiae and poultry feeds, most feed manufacturers add vitamins (qv) and trace minerals to ensure an adequate supply of essential nutrients. Amino acids (qv) such as methionine [7005-18-7] lysiae [56-87-17, threonine [36676-50-3] and tryptophan [6912-86-3], produced by chemical synthesis or by fermentation (qv), are used to fortify swiae and poultry diets. The use of these supplements to provide the essential amino acids permits diets with lower total cmde proteia coateat. 

Gelatin can be a source of essential amino acids when used as a diet supplement and therapeutic agent. As such, it has been widely used in muscular disorders, peptic ulcers, and infant feeding, and to spur nail growth. Gelatin is not a complete protein for mammalian nutrition, however, since it is lacking in the essential amino acid tryptophan [73-22-3] and is deficient in sulfur-containing amino acids. 

The nutritional value of a proteia can be improved by the addition of amino acids of low abundance ia that proteia. Thus the fortification of plant proteias such as wheat, com, and soybean with L-lysiae, DL-methionine, or other essential amino acids (L-tryptophan and L-threonine) is expected to alleviate some food problems (11). Such fortification has been widespread ia the feedstuff of domestic animals. 

Although essential amino acids are requited by both host and tumor, deprivation of select essential amino acids for 2—3 weeks is tolerated by the host yet exerts a pronounced antiproliferative effect on the tumor. Thus, treatment of mice with indole-3-alkane-a-hydroxylase [63363-76-8] from Pseudomonas, which transforms L-tryptophan [73-22-3] to 3-indolylglycaldehyde, lowers the concentration of L-tryptophan in plasma, brain, and lungs, and inhibits the growth of a variety of tumors (32—34). 

A vitamin is defined as an organic compound that is required in the diet in small amounts for the maintenance of normal metabofic integrity. Deficiency causes a specific disease, which is cured or prevented only by restoring the vitamin to the diet (Table 45-1). However, vitamin D, which can be made in the skin after exposure to sunhght, and niacin, which can be formed from the essential amino acid tryptophan, do not stricdy conform to this definition. 

Niacin was discovered as a nutrient during studies of pellagra. It is not strictly a vitamin since it can be synthesized in the body from the essential amino acid tryptophan. Two compounds, nicotinic acid and nicotinamide, have the biologic activity of niacin its metabolic function is as the nicotinamide ring of the coenzymes NAD and NADP in oxidation-reduction reactions (Figure 45-11). About 60 mg of tryptophan is equivalent to 1 mg of dietary niacin. The niacin content of foods is expressed as mg niacin equivalents = mg preformed niacin + 1/60 X mg tryptophan. Because most of the niacin in cereals is biologically unavailable, this is discounted. 

The first step in the synthesis of 5-HT is hydroxylation of the essential amino acid, tryptophan, by the enzyme tryptophan hydroxylase (Fig. 9.4). This enzyme has several features in common with tyrosine hydroxylase, which converts tyrosine to /-DOPA in... 

Figure 9.4 The synthesis and metabolism of 5-HT. The primary substrate for the pathway is the essential amino acid, tryptophan and its hydroxylation to 5-hydrox5dryptophan is the rate-limiting step in the synthesis of 5-HT. The cytoplasmic enzyme, monoamine oxidase (MAOa), is ultimately responsible for the catabolism of 5-HT to 5-hydroxyindoleacetic acid...

There are a few substances that can reduce serotonin, norepinephrine and/or dopamine rapidly and substantially, reducing them to levels thought to be lower than those of depressed patients.23 That is what reserpine was supposed to do and, as we have seen, it did not cause depression - despite the early clinical impression that it did. Other substances have been used in later studies, the most common of which are amino-acid mixtures that lack the essential amino acids needed by the body to produce these neurotransmitters. For example, having people drink a beverage that is rich in amino acids, but does not contain tryptophan (the amino acid needed to produce serotonin), lowers their serotonin levels within a couple of hours. 

Deficiency of essential amino acid precursors in the diet can cause a dysregulation of neurotransmitter activity (e.g, L-tryptophan deficiency causes a decrease in 5-HT and melatonin synthesis and activity). Deficiency in essential fatty acids (e.g, omega-3 fatty acids) can cause a dysregulation of neurottansmitter... 

The non-meat protein product must have biological quality of protein (including amino acids added) of not less than P.E.R. 2.0 (80% of casein) or an essential amino acid content (excluding tryptophan) of no less than 28% of total protein. 

By the 1930s many workers had shown that nutritionally inadequate proteins, such as zein from maize, could be effective as a source of nitrogen if supplemented by additional amino acids (for zein, tryptophan). Even if it contained all the essential amino acids, the amount of protein in the diet influenced the results. Osbome and Mendel found that if the diet contained 18% by weight casein, which is low in cystine, young rats grew, but if the amount of protein was diminished, added cystine was required to offset the relative deficiency of this amino acid. Later, after methionine had been discovered, it was shown to replace the need for cystine. 

Free tryptophan is transported into the brain and nerve terminal by an active transport system which it shares with tyrosine and a number of other essential amino acids. On entering the nerve terminal, tryptophan is hydroxylated by tryptophan hydroxylase, which is the rate-limiting step in the synthesis of 5-HT. Tryptophan hydroxylase is not bound in the nerve terminal and optimal activity of the enzyme is only achieved in the presence of molecular oxygen and a pteridine cofactor. Unlike tyrosine hydroxylase, tryptophan hydroxylase is not usually saturated by its substrate. This implies that if the brain concentration rises then the rate of 5-HT synthesis will also increase. Conversely, the rate of 5-HT synthesis will decrease following the administration of experimental drugs such as para-chlorophenylalanine, a synthetic amino acid which irreversibly inhibits the enzyme. Para-chloramphetamine also inhibits the activity of this enzyme, but this experimental drug also increases 5-HT release and delays its reuptake thereby leading to the appearance of the so-called "serotonin syndrome", which in animals is associated with abnormal movements, body posture and temperature. 

The test is commonly employed as an initial screen for genotoxic activity and, in particular, for point mutation-inducing activity. It detects point mutations, which involve substimtion, addition or deletion of one or a few DNA base pairs. The reverse mutation test in either Salmonella typhimurium or Escherichia coli detects mutation in an amino acid requiring strain (histidine or tryptophan, respectively) to produce a strain independent of an outside supply of amino acid. The principle of the test is that it detects mutations, which revert mutations present in the test strains and restore the functional capability of the bacteria to synthesize an essential amino acid. The revertant bacteria are detected by their ability to grow in the absence of the amino acid required by the parent test strain. 

Following the initial CSF findings, other serotonergic methods have added to our knowledge of its role in aggression. Tryptophan, the essential amino acid precursor to serotonin, has been studied via depletion and... 

Because of their unique biological functions, a significant and growing part of new drug discovery and development is focused on this class of biomolecules. Their biological functions are determined by the exact arrangement, or sequence of different amino acids in their makeup. There are 20 naturally occurring amino acids, 8 of which are essential amino acids, namely, l-isoleucine, L-leucine, L-lysine, L-methionine, L-phenylalanine, L-valine, l-threonine, and L-tryptophan. 

Protein hydrolysis in 6N HCl and subsequent analysis to determine amino acids (except tryptophan, which is acid labile) chemically present is a first step in protein quality evaluation. The chemical score and the EAA index represent attempts to use this information to chemically estimate nutritional quality of protein their obvious limitation is their disregard for amino acid availability. The chemical score is obtained by evaluating the percent of the limiting amino acid in comparison to that amino acid in whole egg protein ). The EAA index is the geometric mean of the ratios of each of the essential amino acids to those amino acids occurring in whole egg (4). 

Among the essential amino acids, the aromatic amino acids (phenylalanine, tyrosine, and tryptophan) form by a pathway in which chorismate occupies a key branch point. Phosphoribosyl pyrophosphate is a precursor of tryptophan and histidine. The pathway to histidine is interconnected with the purine synthetic pathway Tyrosine can also be formed by hydroxylation of phenylalanine (and thus is considered conditionally essential). The pathways for the other essential amino acids are complex. 

Important indole derivatives (see Scheme 2) include (i) indigo, a vat dye known and widely used since antiquity, and originally obtained from indican, a (3-glucoside of indoxyl which occurs in some plants. Indigo is now prepared synthetically. Tyrian purple, a natural dye used since classical times, is 6,6 -dibromoindigo (ii) the numerous indole alkaloids, with complex derivatives such as yohimbine and strychnine (iii) tryptophan, an essential amino acid found in most proteins. Its metabolites include skatole and tryptamine and (iv) 3-indoleacetic acid, which is important as a plant growth hormone. 

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