Introduction To Amino Acids
The twenty amino acids (that make up proteins)each have assigned to them both three-letter (can be upper or lower case) and one-letter codes (upper case). This makes it quicker and easier for notation purposes and are worth learning. The following list gives these notations along with hypertext references to download amino acid gif images and also interactive molecules.The format of the list is: amino acid name - 3 letter code - 1 letter code (reference to gif image, reference to interactive molecule)
Alanine - ala - An amino acid, one of the 20 building blocks of protein. Alanine is not an "essential" amino acid. It is not essential to the diet, but can be made by the body from other substances. Alanine was discovered in protein in 1875. Symbol: Ala.
Arginine - arg - R - Arginine is not an "essential" amino acid. It is not essential to the diet, but can be made by the body from other substances. However, it is usually considered essential to the diet for children so they can grow normally. Lack of arginine in the diet impairs growth and in adult males it decreases the sperm count.
Arginine is available in foods such as turkey, chicken and other meats and as L-arginine in supplements.
Babies born without an enzyme called phosphate synthetase have arginine deficiency syndrome. Adding arginine to their diet permits normal growth and development.
Arginine is the direct metabolic precursor (forerunner) of urea the dominant nitrogenous waste product. Arginine was discovered in protein in 1895. It is abbreviated Arg.
Asparagine - asn - N - Asparagine is nonessential to the diet since the body can synthesize it. Asparagine is important to the metabolism of ammonia. It was the first amino acid to be isolated from a natural source, asparagus juice (1806). Symbol: Asn.
Aspartic acid - asp - D - A amino acid that is not essential to the human diet, aspartic acid was discovered in protein in 1868. It has a role as a neurotransmitter. Symbol: Asp.
Cysteine - cys - C - Cysteine can be synthesized by the body and is not essential to the diet. Its key chemical feature is a thiol group that contains sulfur. This thiol group can combine with the thiol group of another cysteine to form a disulfide bridge, which helps structural proteins and enzymes maintain their configuration. Two cysteine molecules linked by a disulfide bridge make up the amino acid cystine. The symbol for cysteine is Cys.
Glutamine - gln - Q - Glutamine is present in plant and animal proteins. It can be synthesized by the body and is therefore not essential to the diet. Glutamine serves as an important carrier of ammonia and contributes it to the formation of urea and purines (which are essential to make DNA and RNA). Glutamine is broken down in the kidney. It was isolated in 1833 from beet juice but not synthesized until 1933. Symbol: Gln.
Glutamic acid - glu - E - A nonessential amino acid, glutamic acid is present in many animal and plant proteins. It is involved in ammonia metabolism and serves as a neurotransmitter. Glutamic acid was isolated from wheat gluten in 1866 and first synthesized in 1890. Symbol: Glu.
Glycine - gly - G - A nonessential amino acid, glycine is part of many proteins, participates in purine synthesis, and is a neurotransmitter. Symbol: Gly.
Histidine - his - H - An essential amino acid, histidine is present in many proteins. Histidine is elevated in the blood and urine in a genetic condition called histidinemia. Decarboxylation of histidine results in the formation of histamine. Symbol: His.
Isoleucine - ile - I - A dietary essential amino acid, isoleucine is needed for optimal growth in childhood. It is one of the three branched-chain amino acids. Symbol: Ile.
Leucine - leu - L - A dietary essential amino acid, leucine is needed for optimal growth in childhood. It is one of the three branched-chain amino acids. Symbol: Leu.
Lysine - lys - K - A dietary essential amino acid, lysine is present in many proteins and is necessary for optimal growth in childhood. Symbol: Lys.
Methionine - met - M - A dietary essential amino acid, methionine provides methyl groups and sulfur for normal metabolism. Symbol: Met.
Phenylalanine - phe - F - (The human body cannot make it so it is essential to the diet.) Phenylalanine that is ingested is largely transformed (hydroxylated) to form the amino acid tyrosine, which is used in protein synthesis. Too little phenylalanine curbs physical and intellectual growth. Too much phenylalanine, as in phenylketonuria (PKU), is highly toxic to the brain. Phenylanine was first isolated in 1879 and first synthesized in 1882. Symbol: Phe.
Proline - pro - P - A dietary nonessential amino acid, proline is a major constituent of collagen. Symbol: Pro.
Serine - ser - S - A dietary nonessential amino acid, serine is present in many proteins participates in the synthesis of purines and pyrimidines, and is in the active sites of many enzymes. Symbol: Ser.
Threonine - thr - T - A dietary essential amino acid, threonine is necessary for optimal growth in childhood but its exact roles in metabolism are unknown. Symbol: Thr.
Ttryptophan - trp - W - A dietary essential amino acid, tryptophan is necessary for optimal growth of children. Bacteria in the intestine break tryptophan down to compounds that largely are responsible for the unpleasant odor of feces. Symbol: Trp.
Tyrosine - tyr - Y - A nonessential amino acid, tyrosine is produced from another amino acid, phenylalanine. Deficiency of the enzyme phenylalanine hydroxylase that catalyzes this reaction causes the genetic disease called phenylketonuria (PKU). Tyrosine is a precursor of thyroid hormones, catecholamines, and melanin. Symbol: Tyr.
Valine - val - V - A dietary essential amino acid, valine is required for optimal growth of children. It is one of the three branched-chain amino acids. Deficiency of the dehydrogenase enzyme for these branched-chain amino acids causes maple syrup urine disease. Symbol: Val.
Sometimes it is not possible two differentiate two closely related amino acids, therefore we have the special cases:
- asparagine/aspartic acid - asx - B
- glutamine/glutamic acid - glx - Z
- Aliphatic - alanine , glycine , isoleucine , leucine,
- proline valine
- Aromatic - phenylalanine , tryptophan , tyrosine
- Acidic - aspartic acid , glutamic acid
- Basic - arginine , histidine , lysine
- Hydroxylic - serine , threonine
- Sulphur-containing - cysteine , methionine
- Amidic (containing amide group) - asparagine, glutamine
see also: Minerals, Trace Elements and Amino Acids