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# Isoleucine

Protein is one of the most important bio molecules composed of a number of monomer units called as amino acids which play an important roles as an intermediates in metabolism. There are total twenty amino acids found within proteins having a vastarray of chemical versatility. The content and sequence of precise amino acid in a specific protein is determined by the sequence of the bases in the gene which encodes that particular protein.

Proteins control almost all cellular processes and the biological activity of protein is determined by the chemical properties of amino acids. On the basis of need of amino acids in living system, they can be classified in two types.

• Essential amino acids
• Non-essential amino acids
Non-essential amino acids can produce in human body while essential amino acids must be supplied in the food. The deficiency of any one of the essential amino acid results the degradation of proteins and effects metabolism processes. Since amino acids cannot be stores in body like fat and starch, therefore must be supplied in every day food. Plants can synthesize all the amino acids, human body does not have all the enzymes to bio synthesized all the amino acids, therefore must be supplied from diet.

## Isoleucine Structure

Isoleucine amino acid has to provide by food, therefore acts as an essential amino acid. Like leucine and valine, Isoleucine is also a branched amino acid with an aliphatic side chain which is non-polar and hydrophobic in nature. The side chain of Isoleucine along is chiral in nature and forms four steroisomers of isoleucine with two diastereomers. It is coded by AUU, AUA and AUC codons.

Since the side chain of acid is not so reactive, hence cannot bonded covalently on enzyme active centers but important for ligand binding to proteins. The common name of Isoleucine is Î±-Amino-Î²-methylvaleric acid and IUPAC name is 2-Amino-3-methylpentanoic acid. The molecular formula of Isoleucine is C6H13NO2 with molar mass is 131.17 g/mol.

Six forms of Isoleucine are listed in given table with their common name.

 Common names Isoleucine D-Isoleucine L-Isoleucine DL-isoleucine allo-D-isoleucine allo-L-isoleucine allo-DL-isoleucine Synonyms (2R,3R) - Isoleucine (2S,3S) - Isoleucine ($R^{\ast}, R^{\ast}$) - Isoleucine alloisoleucine

The isoelectric point of Isoleucine is 6.05 with pK1=2.4 and pK2=9.7.

Isoleucine was first isolated from fibrin in 1904 and found in most common proteins. The most common sources of Isoleucine are Soy products, meats and fish, dairy Products eggs, legumes and nuts. Some other sources are as follows.

 Food source Amount in per 10gm of substance Egg white, dried 4.581g Soya protein 4.253g Egg whole, dried 2.583g Soy flour, defatted 2.281g Fish, Whitefish 2.280g Chorizo, pork and beaf 2.206g Cheese, parmesan 2.202g Soy meal, defatted 2.180g Seeds, sesame flour 2.157g Milk, buttermilk 2.075g Soybeans, mature seeds, raw 1.971g Cheese, parmesan, grated 1.969g Egg mix 1.938g Cheese, parmesan 1.894g Peanut flour 1.836g Egg yolk 1.734g Cheese, romano 1.732g Soy flour 1.685g Lupins, mature seeds 1.675g Cheese, gruyere 1.615g Cheese, caraway 1.612g Cheese, cheddar 1.563g Spices, parsley, dried 1.546g Cheese, swiss 1.546g Winged beans, mature seeds, raw 1.537g Snacks, pork skins, plain 1.468g Game meat, goat, cooked, roasted 1.382g Beaf, cured, breakfast strips, cooked 1.371g Seeds, sesame flour, high fat 1.352g

Since its an essential amino acid, so cannot synthesized in human body, but in plants and some microorganism, it formed through multistep process where pyruvic acid and alpha-ketoglutarate act as precursor of process and process catalyzed by various enzymes like Acetolactate synthase , acetohydroxy acid isomeroreductase, Dihydroxyacid dehydratase, Valine aminotransferase.

## L-Isoleucine

Except some of the amino acids like taurine, GABA and glycine, amino acids exist in two forms; D or L form which are mirror reverse images of each other. The L form is more common and found in living plants and animal tissues as it is more compatible to human biochemistry than the D form.

The L- form can rotate the plane polarized light to the left i.e. anti-clockwise as well as the amino group is on the L-eft side in its Fisher projection of the compound. The L-form of Isoleucine is as follows.

The L-form can also be shown by R, S system, in which molecule placed in such a way that alpha carbon atom placed in front and H in back side. Than observe the orientation of other groups from Carboxy to amino through alkyl group.

For example, in L-form of Isoleucine at 2nd and 3rd chiral carbon atoms of molecule the CORN circle will form through anti-clockwise movement, hence show S-form and also denotes as (2S,3S) Isoleucine, where 2 and 3 shows the number of carbon atoms in parent chain and S denotes the configuration.