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# Leucine

Proteins are complex substances found in many foods and composed of thousands of small monomer units known as amino acids. They are essential in everybody's diet and act as Building blocks of life.

Amino acids bonded ion various sequences and form different types of proteins found in different foods in our diet. There are only twenty alpha amino acids which involves in the formation of various proteins can be further divided into essential and non-essential amino acids.

1. Essential amino acids must appear in diet as they cannot be synthesized by the body, while non-essential amino acids can be synthesized in human body by biochemical process.
2. Protein rich food breaks down by digestive system to the constituent amino acids, which enter the body "pool" of amino acids.
3. These amino acids are assembling in various sequences to form proteins as per requirement of body.
4. During the deficiency of one or more of the needed amino acids, they cannot be utilized to form a protein, hence a complete diet must contain all of the essential amino acids with additional amino acids for synthesis of the nonessential amino acids.
5. Carbohydrates and fats act as main energy source as proteins release less energy around four kcal per gram.
6. These bio molecules are mainly required for regulation, functions and structure of the cells, tissues, and organs of body.
7. Each protein has unique functions and act as key to muscle building and development.
8. Proteins act as major structural component of all body tissue and also a functional component of hormones and enzymes.
Generally proteins are constantly being broken down in our bodies and amino acids are reused for the formation of other proteins and completely used amino acids are replaced by new one through the process of protein turnover.

## What is Leucine?

Leucine is a branched, aliphatic $\alpha$-amino acid with the chemical formula $\mathbf{HO_{2}CCH(NH_{2})CH_{2}CH(CH_{3})_{2}}$ and molecular mass is 131.17 g $mol^{-1}$. Because of the presence of aliphatic isobutyl side chain, Leucine is hydrophobic in nature. There are six codons for Leucine CUU, CUC, UUA, UUG, CUG and CUA.

Leucine acts as a major component for astacin, ferritin, and other 'buffer' proteins. Leucine is quite similar to valine, has only one additional methylene group in its side chain. Because of hydrophobic nature leucine is generally buried in folded proteins.

Leucine is an essential amino acid, hence cannot be manufactured in the body and must be taken in diet or as supplements. The major sources of leucine amino acid are as follow.

Pyruvic acid acts as a precursor for the synthesis of leucine which catalyzed by a series of enzymes, Acetohydroxy acid isomer reductase, $\alpha$-Isopropylmalate isomerise, Acetolactate synthase, $\alpha$-Isopropylmalate synthase leucine aminotransferase and Dihydroxyacid dehydratase in plants and other micro organism.

Leucine can also be synthesized by using $\alpha$-ketoisovalerate which is an intermediate in the valine synthesis. In synthesis process, Acetyl-CoA acts as acetyl donor for reactant Electrons are transferred to NAD+ followed by decarboxylation process and in the final step, glutamate transfers one amine group to $\alpha$-ketoisocaproate and form leucine.

## Leucine Structure

Leucine is one of the essential amino acid out of ten acids contains one side branched aliphatic side chain with amino and carboxyl group. The pKa1 ($\alpha$-carboxyl group) for leucine is 2.40, pKa2 ($\alpha$-ammonium ion) is 9.60 with isoelectric point 5.98 for leucine.

## Leucine Benefits

1. L-Leucine regulates the blood sugar levels and also increases growth hormone production. It combines with other branched amino acids like iso-leucine and valine to protect and provide fuel to the muscles to increase endurance level and boost energy.
2. L-Leucine involves in the preservation of lean muscle mass and helps to preserve muscle tissue during the aging process. This amino acid can also involve speeding up the recovery process for muscle damage and skin injuries.
3. L-Leucine regulates the protein synthesis and essential in the building of muscle tissue.
4. A sufficient level of Leucine amino acid helps to prevent tissue catabolism and in the rebuilding of muscle tissue after intense training. It also helps to increase endurance and energy to promote muscle tissue health and protection, hence good for bodybuilding.
5. Leucine regulates the growth and repair of muscle tissue like bones, skin and muscles and wound healing. L-leucine is also be beneficial for in phenylketonuria disease in which the body cannot metabolize the amino acid phenylalanine amino acid.
6. The deficiency of L-leucine causes hypoglycemia with irritability, depression, dizziness, fatigue, confusion, headaches, etc.
7. The group of branched-chain amino acids (BCAA) includes leucine, isoleucine, and valine which are excellent sources of energy production in skeletal muscle and serving as building blocks for muscle protein synthesis.
8. Leucine acts as a primary mediator of the metabolic changes during consumption of high protein diet. It also involves in the activation of the metabolic regulatory kinase known as mammalian target of rapamycin, mTOR which increase the rate of protein synthesis and regulates the feeding behaviors.
9. Leucine is the most effective branched-chain amino acids (BCAA) compare to other amino acids as during muscle loss, it breaks down and glucose more quickly compare to isoleucine and valine.
10. Leucine also helps in treatment of traumatic injury and is often recommended for those recovering from surgery.
11. No doubt leucine is an essential amino acid; the excess intake of leucine causes the development of pellagra which is a deficiency of the vitamin niacin.
The main symptoms of pellagra are mental disorders, dermatitis, and diarrhea. The high concentration of leucine can disrupt liver and kidney function in the body.

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