All amino acids are building blocks of proteins, and as such they are an essential part of all body structures. Amino acids may however also have other roles in the body, and some amino acids are of special importance to some body organs or functions. 8 of the amino acids cannot be produced by the body itself, but must be added through the food. These are called essential. The rest can be produced by biochemical reactions within the body.

Chemicaly most amino acids have this composition NH2-CHR-COOH, where R is a group thet varies from amino acid to amino acid. All amino acida have the NH2-group and the -COOH-group. In the simplest amino acid, glycine or glycocol, the R-group (side-chain) is just a hydrogen atom, so glycine has the formula NH2-CH2-COOH. The next simplest amino acid, cerine, has the group -CH3 as a side chain, and thus has the formula NH2-CH(CH3)-COOH. The NH2-group is actually basic, it can attract a proton and become -NH3+.  The -COOH-group is acidic and can give a proton away and become -COO-. An amino acid can therefore react with itself, and mostly do so, to get into the form COO--CHR-NH3+. The ability to react this way, that is as an ampholyte, is important for the biological role of amino acids.

When amino acids chain together to make protein molecules, the carboxylic group of one amino acid reacts with the amino group of the other by shedding a hydrogen atom and an -OH group that combines to water. The result is water molecules and a long chain with this structure:

NH2-CHR-CONH-CHR-CONH-CHR----------CONH-CHR-COOH

Such a chain will fold iteslf together in a specific shape and be hold together by weaker bonds, so-called hydrogen bonds. Two or more folded chains can also react and bind to each other, mainly by bindings between sulphur atoms, di-sulphide bindings (-s-s-) between two cystein-units, cystein is a sulphur-containing amino acid.

Proteins have three main roles in the body.

- They are building elements of cells and substances between cells.

- They act as enzymes, that is: They help speed up important reactions that the life processes consist of.

- They act as motoric units with the ability to contract, and thus enabeling muscle cells to work and enabeling movements within all cells.

Amino acids also have the role as raw mqterial for the syntesis of meny hormons. For example is the amono acid thyrosine used to make the hormones of the thyroid gland.

The hormone insuline is a protein, or polypeptide and is thus composed of a chain of amino acids. The growth hormone is also a protein.

The animal kingdom is a rich source of proteins with an amino acid mix that is well suitable for humans. Fish, seafood and lean meat are good diet ingredients to get proteins.

Cheese and diery products are also good sources of full value protein. Mushrooms are rich sources of proteins when they have been damoted to a smaller size. Fresh mushrooms contain very much water.

Nuts, sunflower seeds and almonds are also good sources of proteins. However, protein sources from the plant kingdom tend to be deficient in some amino acids, especially methionine. By combining diery products with cereals one also gets a full value mix of amino acids.

About glutamic acid and glutamat - an essential amino acid

The chemistry of glutamic acid

Glutamic acid has the formula HOOC-CH2-CH2-CH(NH2)-COOH. Since it has a doble carboxylic acid group it is an mailnly acidic substance. The form of the substance where one or two hydrogen atoms are splitt off is called glutamate. Glotamate is found bound to metallic ions making salts, for example mono-sodium-glutamate.

The role of glutamic acid in the body

Glutamic acid is an essential amino acid and it is an important component in most proteins.

Glutamate is an internediary in many important biochemical rection chains in the body, especially the citric acid cycle that furnishes the body with the substance ATP, containing energy redy for immediate use

Glutamate is also an important transmittor substance in the brain and elsewhere in the central nervous system, that is a substance that carry nerve signal from one nerve cell to another. Glutamate is an exitartory neurotransmittor,  that is it stimulates the resceiving cell to send more signals further.

Some of the structures that cach up glutamate in the brain celle, the NMDA receptors, will permanently bind glutamate and thus permanently make the cell more eager to send signals along to new cells. Because of this glutamate is thought to be important in the memory process.

The toxic effect of to high glutamate concentration

By brain injury or some brain diseases too much glutamate is found around the nerve cells, because the glial celle do not manage to clean out excessive glutamate. This cause too many channels connected with NMDA resceptors to leak calcium into the cell, and this calcium can cause cell death, a process called called exitotoxicity.

Excitotoxicity from excessive glutamate occurs as part of the ischemic cascade, that is injury of nervous tissue due to lack of oxygen. Such injury occurs by conditions like amyotrophic lateral sclerosis, lathyrism, autism, some forms of mental retardation and Alzheimer's disease.

Glutmate as an added substance to the food

About tryptophan - an essential amino acid

The role of thryptophan in the body

For many organisms including humans, tryptophan is an essential amino acid. This means that it cannot be synthesized by the organism and therefore must be part of its diet. The principle function of amino acids including tryptophan are as building blocks in protein biosynthesis. In addition, tryptophan functions as a biochemical precursor for the following:

Serotonin (a neurotransmitter), via tryptophan hydroxylase. Serotinin, in turn, can be converted to melatonin (a neurohormone), via 5-hydroxyindole-O-methyltransferase
Niacin (with kynurenine as an intermediate)

Many molecules are found in two geometrical variants, of which one rotates polarized light leftwise (levo), and the other rotates polarized light rightwise (dekstro). The variant of tryptophan used in the human body is Levo-tryptophan or l-tryptophane.

In organisms which synthesize tryptophan, high levels of this amino acid activate a repressor protein which in turn binds to the trp operon. Binding of this repressor to its operon prevents transcription of downstream DNA which codes for enzymes involved in the biosynthesis of tryptophan. Hence high levels of tryptophan prevent additional tryptophan synthesis through a negative feedback loop. Conversely if the cell's tryptophan level drops, transcription of the operon's genes resumes. This is one example of how gene expression responds rapidly to changes in the cell's internal and external environment.
 

Uses as a dietary supplements

Tryptophan, found as a component of dietary protein, is particularly plentiful in chocolate, oats, bananas, dried dates, milk, yogurt, cottage cheese, red meat, eggs, fish, poultry, sesame, chickpeas, sunflower seeds, pumpkin seeds,spirulina and peanuts. It is found in turkey at a level typical of poultry in genera.

Uses as a dietary supplement

For some time, tryptophan was available in health food stores as a dietary supplement. Since 2002, L-Tryptophan has been sold again in its original form. Many people found tryptophan to be a safe and reasonably effective sleep aid, probably due to its ability to increase brain levels of serotonin (a calming neurotransmitter when present in moderate levels) and/or melatonin (a sleep-inducing hormone secreted by the pineal gland in response to darkness or low light levels).

Clinical research tended to confirm tryptophan's effectiveness as a natural sleep aid and for a growing variety of other conditions typically associated with low serotonin levels or activity in the brain. (Particularly work by Dr. Richard Wurtman at MIT). In particular, tryptophan showed considerable promise as an antidepressant alone, and as an "augmenter" of antidepressant drugs. Other promising indications included relief of chronic pain and reduction of impulsive, violent, manic, addictive, anxiety-related, obsessive, and compulsive behaviours and disorders.

In 1989, a large outbreak of a new, disabling, and in some cases deadly autoimmune illness called eosinophilia-myalgia syndrome (EMS) was traced to one source of L-tryptophan. The bacterial culture used to synthesize tryptophan by a major Japanese manufacturer, Showa Denko KK, had been genetically modified several times to increase tryptophan production during the 1980s.

Along with the higher tryptophan concentrations in the modified culture media, the purification process had also been streamlined to reduce costs, and a purification step that used charcoal absorption to remove some impurities had been omitted.[5] The manufacturer maintained that this process modification allowed another bacterial metabolite through the purification, resulting in the presence of an end-product contaminant responsible for the toxic effects. As of 1996, Showa Denko had destroyed all modified organisms without FDA receipt of culture samples.The FDA was unable to publicly establish with certainty what contaminant was the cause of the outbreak.

Most tryptophan was banned from sale in the US in 1991, and other countries followed suit. Tryptophan from one manufacturer, of six, continued to be sold for manufacture of baby formulas. A Rutgers Law Journal article observed, “Political pressures have played a role in the FDA’s decision to ban L-tryptophan as well as its desire to increase its regulatory power over dietary supplements.”[8]

At the time of the ban the FDA did not know, or did not indicate, that EMS was caused by a contaminated batch, and yet even when the contamination was discovered and the purification process fixed, the FDA maintained that L-tryptophan was unsafe. In February 2001 the FDA loosened the restrictions on marketing (though not on importation), but still expressed the following concern:

"Based on the scientific evidence that is available at the present time, we cannot determine with certainty that the occurrence of EMS in susceptible persons consuming L-tryptophan supplements derives from the content of L-tryptophan, an impurity contained in the L-tryptophan, or a combination of the two in association with other, as yet unknown, external factors."

Uses as medication

5-Hydroxytryptophan (5-HTP), a metabolite of tryptophan, has been suggested as a treatment for epilepsy and depression though clinical trials are inconclusive and lacking.

5-HTP readily crosses the blood brain barrier and in addition is rapidly decarboxylated to serotonin (5-hydroxytryptamine or 5-HT). and therefore may useful for the treatment of depression. However serotonin has a relatively short half life since it is rapidly metabolized by monoamine oxidase therefore is likely to have limited efficacy. It is marketed in Europe for depression and other indications under brand names like Cincofarm and Tript-OH.

In the United States, 5-HTP does not require a prescription as it is covered under the Dietary Supplement Act. However, since the quality of dietary supplements are not regulated by the FDA, the quality of dietary and nutritional supplements tends to vary and there is no guarantee that the label accurately depicts what the bottle contains.[citation needed]

In recent years, compounding pharmacies and some mail-order supplement retailers have begun selling tryptophan to the general public. Tryptophan has also remained on the market as a prescription drug (Tryptan) which some psychiatrists continue to prescribe, particularly as an augmenting agent for people who are unresponsive to antidepressant drugs.[citation needed] Also, most health-food stores sell 5-HTP to get around the resulting artificially high cost of the amino acid itself. But several high quality sources of L-Tryptophan do exist, and are sold in many of the largest health food stores nationwide. Indeed, tryptophan has continued to be used in clinical and experimental studies employing human patients and subjects. Several of these studies suggest tryptophan can effectively treat the fall/winter depression variant of seasonal affective disorder (SAD).