Amino Acids | History | Structure | List of Amino acids | Industry application.....
AMINO ACIDS-
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| Amino Acid |
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Amino acids are organic compounds that combine to form proteins. Amino acids and proteins are the building blocks of life.
The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids. They can be classified according to the core structural functional groups' locations as alpha- (α-), beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other categories relate to polarity, pH level, and side chain group type (aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid residues form the second-largest component (water is the largest) of human muscles and other tissues.
In biochemistry, amino acids having both the amine and the carboxylic acid groups attached to the first (alpha-) carbon atom have particular importance. They are known as 2-, alpha-, or α-amino acids; often the term "amino acid" is used to refer specifically to these.
They include the 22 proteinogenic ("protein-building") amino acids, which combine into peptide chains ("polypeptides") to form the building blocks of a vast array of proteins. These are all L-stereoisomers ("left-handed" isomers), although a few D-amino acids ("right-handed") occur in bacterial envelopes, as a neuromodulator (D-serine), and in some antibiotics. Twenty of the proteinogenic amino acids are encoded directly by triplet codons in the genetic code and are known as "standard" amino acids. The other two ("nonstandard" or "non-canonical") are selenocysteine (present in many prokaryotes as well as most eukaryotes, but not coded directly by DNA), and pyrrolysine (found only in some archaea and one bacterium).
Because of their biological significance, amino acids are important in nutrition and are commonly used in nutritional supplements, fertilizers, feed, and food technology. Industrial uses include the production of drugs, biodegradable plastics, and chiral catalysts.
HISTORY :-
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| Louis-Nicolas Vauquelin and Pierre Jean Robiquet |
The first few amino acids were discovered in the early 19th century. In 1806, French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, the first amino acid to be discovered. Cystine was discovered in 1810, although its monomer, cysteine, remained undiscovered until 1884. Glycine and leucine were discovered in 1820. The last of the 20 common amino acids to be discovered was threonine in 1935 by William Cumming Rose, who also determined the essential amino acids and established the minimum daily requirements of all amino acids for optimal growth. First use of the term "amino acid" in the English language dates from 1898, while the German term, Aminosäure, was used earlier. Proteins were found to yield amino acids after enzymatic digestion or acid hydrolysis.
General Structure :-
Isomerism - The alpha amino acids are the most common form found in nature, but only when occurring in the L-isomer. The alpha carbon is a chiral carbon atom, with the exception of glycine which has two indistinguishable hydrogen atoms on the alpha carbon. Therefore, all alpha amino acids but glycine can exist in either of two enantiomers, called L or D amino acids (relative configuration), which are mirror images of each other. While L-amino acids represent all of the amino acids found in proteins during translation in the ribosome, D-amino acids are found in some proteins produced by enzyme post-translational modifications after translation and translocation to the endoplasmic reticulum, as in exotic sea-dwelling organisms such as cone snails.
Side chains - Amino acids are designated as α- when the nitrogen atom is attached to the carbon atom adjacent to the carboxyl group: in this case the compound contains the substructure N–C–CO2. Amino acids with the sub-structure N–C–C–CO2 are classified as β- amino acids. γ-Amino acids contain the substructure N–C–C–C–CO2, and so on. Amino acids are usually classified by the properties of their side chain into four groups. The side chain can make an amino acid a weak acid or a weak base, and a hydrophile if the side chain is polar or a hydrophobe if it is nonpolar. The phrase "branched-chain amino acids" or BCAA refers to the amino acids having aliphatic side chains that are linear; these are leucine, isoleucine, and valine. Proline is the only proteinogenic amino acid whose side-group links to the α-amino group.
Zwitterion - In aqueous solution amino acids exist in two forms, the molecular form and the zwitterion form in equilibrium with each other. The two forms coexist over the pH range pK1 − 2 to pK2 + 2, which for glycine is pH 0–12. The ratio of the concentrations of the two isomers is independent of pH. It is generally assumed that the concentration of the zwitterion is much greater than the concentration of the neutral molecule on the basis of comparisons with the known pK values of amines and carboxylic acids.
Isoelectric point - The variation in titration curves when the amino acids can be grouped by category.[clarification needed] With the exception of tyrosine, using titration to distinguish among hydrophobic amino acids is problematic. At pH values between the two pKa values, the zwitterion predominates, but coexists in dynamic equilibrium with small amounts of net negative and net positive ions. Amino acids have zero mobility in electrophoresis at their isoelectric point, although this behaviour is more usually exploited for peptides and proteins than single amino acids.
SYNTHESIS :-
Chemical synthesis - The commercial production of amino acids usually relies on mutant bacteria that overproduce individual amino acids using glucose as a carbon source. Some amino acids are produced by enzymatic conversions of synthetic intermediates. 2-Aminothiazoline-4-carboxylic acid is an intermediate in one industrial synthesis of L-cysteine for example. Aspartic acid is produced by the addition of ammonia to fumarate using a lyase.
Biosynthesis - In plants, nitrogen is first assimilated into organic compounds in the form of glutamate, formed from alpha-ketoglutarate and ammonia in the mitochondrion. For other amino acids, plants use transaminases to move the amino group from glutamate to another alpha-keto acids. For example, aspartate aminotransferase converts glutamate and oxaloacetate to alpha-ketoglutarate and aspartate. Nonstandard amino acids are usually formed through modifications to standard amino acids. For example, homocysteine is formed through the transsulfuration pathway or by the demethylation of methionine via the intermediate metabolite S-adenosylmethionineS-adenosylmethionine, while hydroxyproline is made by a post translational modification of proline.
USES IN INDUSTRY :-
1) Animal feed
2) Food Industry
3) Synthesis of drug and cosmetics
4) Pharmaceutical industry
5) Treatment of sleeping sickness
6) Expanded genetic code
7) Nullomers
8) Chemical building blocks
9) Biodegradable plastics
10) Industries
Lists of Amino Acids :-
1) Alanine
2) Cysteine
6) Glycine
7) Histidine
8) Isoleucine
9) Lysine
10) Leucine
11) Methionine
12) Asparagine
13) Proline
14) Glutamine
15) Arginine
16) Serine
17) Threonine
18) Valine
19) Tryptophan
20) Tyrosine
21) Selenocysteine
22) Pyrrolysine
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