Introduction to Amino Acids
AMINO ACIDS are found in all foods except oil. Despite claims to the contrary, all vegetables, legumes, and grains contain all the essential amino acids. They may not contain high amounts of some, but, if combined with another vegetable source, all the essential amino acid requirements are met.
There are about eighty amino acids found in nature, but only twenty to twenty-nine are required for human growth. This figure depends upon the source consulted but most agree the figure is twenty or twenty-one. Once again, depending on the source, eight to ten amino acids are considered essential for life. The reason for the classifications of amino acids into "essential" and "non-essential" was to distinguish between those the body could manufacture and the ones that had to come from diet.
Essential amino acids are those that must come from the diet. These include: isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Non-essential amino acids are those that the body can manufacture from an available source of nitrogen and a carbon skeleton. These include: alanine, asparagine, aspartic acid, carnitine, citrulline, cysteine, cystine, GABA, glutamic acid, glutamine, gluthathione, glycine, hydroxyproline, ornithine, proline, serine, taurine, and tyrosine.
Semi-essential amino acids are ones that can sometimes be made internally if conditions are right. Arginine and histidine can be converted from other amino acids if needed. Methionine can be converted to cystine, but cystine cannot be converted to methionine. Phenylalanine can be converted to tyrosine, but not the other way around. Therefore, when cystine and tyrosine are present in the diet, the requirements for methionine and phenylalaine are reduced. Thus, cystine and tyrosine are sometimes classified as "semi-essential." The liver is able to produce 80% of the amino acids it needs for protein construction, while the remaining 20% must be consumed.
Proteins are classified according to:
1) composition and chemical properties, ie., simple, conjugated, compound, or derived
2) nutritional quality, ie., complete, partially complete, or incomplete
3) structure, ie., fibrous or globular
4) solubility in water, acid, or alcohol.
Based on their content of amino acids, foods are often classified as complete, partially complete, or incomplete protein sources. In order for a protein to be complete, it must contain all of the essential amino acids. This is the reason that many nutritionists rank non-meat foods as being incomplete. The foods do contain all amino acids, but some may be in lower proportions than are required, and, therefore, should be combined with another food containing higher amounts of these amino acids.
Amino acid construction consists of carbon, hydrogen, oxygen, and nitrogen with some containing sulfur. Every amino acid, with the exception of glycine, comes in two forms -- a left-handed (L) version and a right-handed (D) version, which are identical mirror images of each other. However, protein chains cannot be formed from a mixture of D and L amino acids. An L series is found naturally in plant and animal sources. Over-the-counter supplements in an L series are more preferable since they are more compatible to the human makeup.
The body uses, almost without exception, from the L forms, but some D forms have been used therapeutically. The one exception is with phenylalanine, which can appear as both an L and a DL configuration. The DL supplements are generally chemically manufactured and are not as easily assimilated as the L configuration.
In order for the protein-building process to occur in the body, there must be enough quality protein in the diet; and that protein must be easily digestible in order for the breakdown (catabolism) and rebuilding (anabolism) of vital nutrients to occur. The body continually breaks down protein molecules and rebuilds the resulting amino acids into other usable chains required by particular areas of the body. Amino acids compete with each other for entry to the brain. Therefore, to avoid this competition, amino acid supplements should be taken on an empty stomach.
In addition to their main functions of building needed proteins, amino acids also assist vitamins and minerals to do their jobs properly. Even if vitamins and minerals were absorbed and assimilated rapidly, they would not be as effective as they are in the presence of amino acids. In order to be properly assimilated, amino acids particularly require the help of Vitamins B12, Bw, C, and T, chromium, and sleep.
Vegans must be aware that most of the amino acid supplements available have an animal-base. There are supplements -- derived from vegetable sources -- in a crystalline free form that are more stable and preferable because of their rapid absorption. However, labels must be read carefully.
Also, beware of alkali-treated soy products. This treatment tends to reduce three amino acids -- lysine, serine, and cystine -- as well as produce a toxic amino acid derivative called lysinoalanine. In addition, more people are showing allergy symptoms toward soy products, which may or may not be as a result of products using genetically engineered soybeans.
Amino acids are actively transported, but also require a carrier; and each carrier is specific to certain amino acids. For example:
Carrier 1 is for serine, threonine, and alanine.
Carrier 2 is for phenylalanine, tyrosine, methionine, valine, leucine, and isoleucine.
Carrier 3 is for proline and hydroxyproline.
Carrier 4 is for taurine and B-alanine.
Carrier 5 is for lysine, arginine, cysteine.
Carrier 6 is for aspartic acid and glutamic acid.
Chemical Division for Amino Acids:
1. Aromatic Amino Acids: Phenylalanine, Tyrosine, Tryptophan
2. Sulfur Amino Acids: Cysteine, Gluthathione, Taurine, Methionine, Homocysteine
3. Urea Cycle Amino Acids: Arginine, Citrulline, Ornithine
4. Glutamate Amino Acids: Glutamic Acid, GABA and Glutamine; Proline and Hydroxyproline; Aspartic Acid-Asparagine
5. Threonine Amino Acids: Threonine; Glycine; Serine; Alanine
6. Branched Chain Amino Acids (BCAA): Leucine, Isoleucine, and Valine
7. Important Metabolite Amino Acids: Lysine; Carnitine; Histidine
Diseases directly related to amino acid metabolism difficulties (Thorsons):
Alanine: (Lactic acidosis)
Arginine: (Hyperargininaemia)
Argininosuccinic acid: (Arginosuccinicaduria)
b-Alanine: (Beta-alaninaemia)
Citrulline: (Citrullinaemia)
Cystine: (Cystinosis and Cystinuria)
Glutamic acid: (Pyroglutamic acidaemia)
Glycine: (Nonketotic hyperglycinaemia and Ketotic hyperglycinaemia)
Histidine: (Histidinaemia)
Homocystine: (Homocystineuria)
Isoleucine: (Propionic acidaemia and MSUD - Maple Syrup Urine Disease)
Leucine: (Isovaleric acidaemia and MSUD)
Lysine: (Hyperlysinaemia)
Methionine: (Hypermethioninaemia)
Ornithine: (Hyperornithinaemia and Ornithine aminotransferase deficiency)
Phenylalanine: (Phenylketonuria - PKU and Atypical PKU)
Pipecolic acid: (Hyperpipecolicaemia and Zellwagers' syndrome)
Proline: (Hyperprolineaemia I and II)
Serine: (Hyperoxaluri II)
Threonine: (Hyperthreoninaemia)
Tryptophan: (Tryptophanuria)
Tyrosine: (Hereditary tyrosinaemia)
Valine : (Hypervalinaemia)
