#Amino acids

December 28, 2011 by  
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Commonly referred to as ‘the building blocks of protein’, amino acids are needed to make almost all components of the body including enzymes, blood corpuscles, hormones, antibodies, hair, skin, bone and tissues.

Amino acids are generally linked together by peptide bonds, to form peptides. When ten or more are linked, these are known as polypeptides. Very large polypeptides are known as proteins. Amino acids are often classified according to whether they are ‘essential’ or ‘non-essential’. This is a potentially misleading description since it is sometimes assumed to mean that most amino acids do not play an essential role in the body. In fact the term ‘essential’ does not refer to the role of the amino acids but to the body’s ability to synthesize them. ‘Essential’ amino acids are those which the body is incapable of synthesizing and which must, therefore, be obtained from the diet. Although equally important, amino acids such as taurine, carnitine and tyrosine can, at least in healthy individuals, be synthesized from other amino acids and are therefore described as ‘non-essential’.

Some authorities have made statements that amino acid supplementation is valueless because most people in the western world already eat too much protein. However this fails to take account of individual biochemistry and possible errors of metabolism. Some people may be less capable than others of synthesizing ‘non-essential’ amino acids and would therefore benefit from supplementation, especially if they do not regularly consume animal products in their diet.

Amino acids can be divided into a number of categories according to their structure and functions:

  • Amino acids with important metabolites: lysine, carnitine, histidine
  • Aromatic amino acids: phenylalanine, tyrosine and tryptophan
  • Branched chain amino acids: leucine, isoleucine, valine
  • Glutamate amino acids: glutamic acid, GABA, glutamine, proline, hydroxyproline, aspartic acid, asparagine
  • Sulphur amino acids: cysteine, glutathione, taurine, methionine, homocysteine
  • Threonine amino acids: threonine, glycine, serine, alanine
  • Urea cycle amino acids: arginine, citrulline, ornithine

Glucogenic amino acids are those which, after losing their amino group, give rise to metabolic intermediate substances which form glucose. These are: alanine, arginine, aspartic acid, cysteine, glutamic acid, glycine, histidine, hydroxyproline, methionine, proline, serine, threonine and valine.

Amino acids can occur in two isomer forms known as the ‘D’ and ‘L’ forms. This is why you will often see them described as L-tryptophan or L-tyrosine for instance. The ‘D’ form of amino acids is not usually found in nature and, with the exception of D-phenylalanine, is not normally utilizable by the human body.

The so-called essential amino acids

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine

Information compiled by Linda Lazarides
Naturopathic Nutritionist, Author, Educator

Alanine

July 24, 2003 by  
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An amino acid formed from the conversion of pyruvate (a common compound formed during carbohydrate metabolism) or the breakdown of DNA or the dipeptides carnosine and anserine, (this latter process requires a zinc-dependent enzyme) found in large amounts in chicken and turkey.

Alanine helps to prevent exercise-induced ketosis and may reduce the ketosis of diabetes. It can be converted quickly in the liver to usable glucose, thus acting as a major energy source, and by triggering the release of glucagon from the liver, it can stimulate an increase in blood sugar.

Alanine also acts as an inhibitory neurotransmitter and is important in the body’s production of lymphocytes (white blood cells). According to environmental medicine expert Dr William Rea, it is frequently deficient in chemically sensitive individuals, resulting in a slow ability to conjugate toxins.

Information compiled by Linda Lazarides
Naturopathic Nutritionist, Author, Educator

Arginine

July 11, 2004 by  
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Amino acid

Arginine is one of the urea cycle amino acids. It plays an important role in the conversion of ammonia from protein breakdown, into urea which can be excreted via the kidneys, and it stimulates the activity of the enzyme which starts off the process. Arginine is also a component of antidiuretic hormone, a hormone which reduces the excretion of water by the kidneys.

Many people take arginine (together with another amino acid, ornithine) as a body-building supplement. There is some evidence that supplementation with these amino acids may stimulate the release of growth hormone, which is responsible for increasing muscle bulk, and also insulin. The suggested dose is 2 grams of arginine and 2 of ornithine on an empty stomach before retiring, and 2 grams on an empty stomach prior to vigorous exercise. 100 mcg of a chromium supplement may also be helpful. Arginine supplementation should be avoided in cases of schizophrenia and herpes virus.

Arginine-rich foods include nuts, peanuts, seeds, chocolate and grains (cereals). Weight for weight, peanuts, tofu, pumpkin seeds, almonds, sunflower seeds and brazil nuts are as rich in arginine as animal proteins.

Information compiled by Linda Lazarides
Naturopathic Nutritionist, Author, Educator

asparticacid

January 2, 2004 by  
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Aspartic acid

Amino acid

Known as a glutamate amino acid, aspartic acid is made from another amino acid, glutamic acid, by enzymes using vitamin B6. It plays an important part in the urea cycle (the conversion of toxic ammonia from protein breakdown into urea which can be excreted by the kidneys), and in DNA metabolism. Aspartic acid is a major excitatory neurotransmitter). Animal studies have found that both potassium and magnesium aspartate may be able to stimulate the proliferation and differentiation of the thymus gland, bone marrow and spleen tissue, as well as help the red blood cell-producing organs to regenerate after exposure to radiation.

With glutamine, aspartic acid forms asparagine, and with citrulline it forms arginosuccinate. It is involved in oxidative phosphorylation and energy production.

Availability: Not easily available in its pure form. Best taken as mineral aspartates, (e.g. magnesium aspartate).

bcaas

September 28, 2001 by  
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Branched-chain amino acids (also see Amino acids)

These are the three amino acids leucine, isoleucine and valine, comprising about 40 per cent of the total minimum daily requirement for essential amino acids. They are particularly involved in energy and muscle metabolism, and can be used directly as an energy source by muscles. They are also anabolic, promoting protein synthesis.

Branched-chain amino acids (BCAAs) are particularly depleted by stress, and studies have suggested that starvation, injury, surgery or infection raise requirements for BCAAs more than other amino acids. They may be elevated in diabetics since low insulin levels reduce the uptake of BCAA by muscle. BCAAs compete with each other and with tyrosine, phenylalanine, tryptophan and methionine for transport to the brain. BCAAs can act as neurotransmitters and are constituents of neuropeptides which have neurotransmitter functions.

BCAAs stimulate protein synthesis, inhibit protein breakdown, and can substitute for glucose, providing an alternative energy source for the body. Because of their ability to maintain blood sugar levels, some doctors believe that BCAAs may be a more ideal energy source than glucose in intravenous feeding solutions, particularly as they decrease the rate of breakdown and utilization of other amino acids. Nitrogen retention (an indicator of the ability to use protein) in critically ill patients seems to be proportional to the amount of BCAAs, and BCAA supplements seem to be able to correct most hypercatabolic (tissue wasting) states.

Cases of unexplained anorexia may respond to BCAA supplements.

carnitine

October 8, 2006 by  
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Carnitine

Amino acid

The most important function of carnitine is thought to be its role in regulating fat metabolism – carrying fat across a membrane to the energy-burning mitochondria of each cell. The more carnitine is available, the faster fat is transported, and the more fat is used for energy. This is a particularly vital function in the heart muscle.

Carnitine also helps the body to break down branched-chain amino acids into fuel for the muscles when necessary, and it controls ketone levels in the blood. Ketones are the result of the incomplete oxidation of fats in energy production. They are high in diabetics (whose hearts often metabolize carnitine abnormally) and they also rise in high-protein or high-fat diets and tend to acidify the blood.

In a double-blind study which administered 2 grams of carnitine or a placebo to ten volunteers 1 hour before they began working on an exercise cycle, it was found that at the maximum exercise intensity, treatment with L-carnitine significantly increased the maximum oxygen uptake and power output. Oxygen uptake, carbon dioxide production, pulmonary ventilation and plasma lactate were reduced. The researchers concluded that carnitine supplementation results in a more efficient performance at maximum exercise intensity. (Vecchiet L et al: Influence of L-carnitine administration on maximal physical exercise. Eur J Appl Physiol 61(5-6):486-90, 1990.)

cysteine

October 3, 2004 by  
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Cysteine

Amino acid

Cysteine belongs to the sulphur group of amino acids. It is obtained from dietary sources and can also be synthesized from methionine. Cysteine contributes to the structure of proteins, in the form of cystine. (Cystine is created when two molecules of cysteine bond together the two amino acids can for most purpose be considered as the same). It also plays a role in energy metabolism and can be converted to glucose if necessary. Cysteine supply may be a limiting factor for white blood cell (lymphocyte) function. Research has shown that cysteine supply is impaired in a number of conditions associated with immunodeficiency, including Aids.

In the liver, cysteine is used to form the amino acid glutathione which helps to detoxify potentially harmful substances and free radicals. It is also a precursor of the detoxifying amino acid taurine.

A cysteine deficiency can result in allergic-like chemical sensitivities and in abnormal glucose metabolism, since cysteine is involved in glucose metabolism and holds the insulin molecule together.

Do not supplement cysteine or glutathione in insulin-dependent diabetes because cysteine acts as a coenzyme for insulin degeneration.

Vegetarian sources: Weight for weight, soya protein concentrates, almonds, sesame seeds and walnuts are as rich in cysteine as animal proteins.

Availability of supplements: N-acetyl cysteine is becoming the preferred form of cysteine supplementation, and is available in health food shops or through practitioners. As a detoxification aid, the suggested dose is about 1 gram per day.

glutamic-acid

March 10, 2004 by  
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Glutamic acid

Amino acid

Glutamic acid or glutamate can be manufactured by the body. It is a precursor of proline, ornithine, arginine and polyamines. It functions as a stimulatory neurotransmitter and can also be converted by the body into the inhibitory neurotransmitter GABA and the amino acid glutamine, which participates in the production of DNA. Glutamic acid is found in particularly high levels in the brain, for instance in the nerves of the hippocampus, its memory centre.

Researchers working with epileptic patients have found that most epileptics have decreased taurine, GABA and glycine, with increased aspartic acid and glutamic acid. An explanation for this imbalance may be that glutamic acid is not being properly converted to GABA in these patients. The vitamin B6-dependent enzyme glutamate decarboxylase makes GABA from glutamic acid. Vitamin B6 deficiency is known to be associated with seizures and convulsions.

‘Chinese restaurant syndrome’, the symptoms of which include headache, nausea, weakness, flushing and sweating after eating Chinese food, may be due to a high content of monosodium glutamate – a sodium salt of glutamic acid – in the food. Those who suffer from this syndrome may also have reduced levels of glutamate decarboxylate. It has been proposed that this syndrome can be prevented with vitamin B6 supplementation.

glutamine

May 1, 2004 by  
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Glutamine

Amino acid

Glutamine is not found in food. It is primarily a brain fuel which can take the place of glucose. It is particularly abundant in the substantia nigra and thalamus of the brain, as well as in the blood, where its concentration is three to four times greater than all other amino acids. It is 10 to 15 times more concentrated in the cerebrospinal fluid than in the blood. In fasting or starvation states, when glycogen stores have been exhausted, large amounts of glutamine (and alanine) are released from muscle tissue and serve to shuttle amino acid nitrogen and carbon to other tissues. The carbon may be converted to glucose by the liver and made available for energy production.

In the 1960s an experiment was carried out supplementing 15 grams a day of L-glutamine to alcoholics. Compared with placebo, this was found to produce a significant improvement in control over alcohol consumption, but follow-up studies are lacking.

Glutamine also performs a major role in DNA synthesis. An influx of large amounts of glutamine may stimulate muscle protein synthesis. 60 per cent of the ammonia produced in the kidney tubules to buffer excessive urinary acidity comes from the breakdown of glutamine.

glutathione

December 4, 2004 by  
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Glutathione

Amino acid

Glutathione, produced from the amino acid cysteine, is the body’s primary defence against oxidative (free radical) damage within cells. Exposure to toxic chemicals stimulates the secretion of glutathione from the liver into the plasma. Once in the plasma, glutathione complexes (conjugates) with the toxins. The resultant conjugate is then converted to mercapturic acid, which can be excreted by the kidneys. Glutathione also deactivates hydrogen peroxide and other peroxides. Many individuals with chemical sensitivity are deficient in glutathione.

Glutathione is also needed for the production of prostaglandins and it is a coenzyme for the breakdown of insulin in the liver and kidney.

Glutathione can be taken as a dietary supplement, in which case its most effective chemical form is known as reduced glutathione. (Also see Detoxification.)

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