Leucine is the branched-chain amino acid with a non-polar aliphatic side chain. It is an essential amino acid as it cannot be synthesized by the body. So it must be obtained from the foods or diets. It has UUG, UUA, CUC, CUU and CUG codons. Leucine is a ketogenic amino acid.
It is found in foods containing proteins. Its sources are:
Animal sources: Meat, chicken, poultry, fish, seafood, dairy products like cottage cheese etc
Plant sources: Whole lentils, brown rice, nuts, soy flour, whole wheat, beans, sesame seeds and peanuts etc.
Since leucine is not formed in our body but it is synthesized in the plants and some microorganism. In them, it is formed from pyruvate by using following enzymes namely, acetolactate synthatase, dihydroxyacid dehydratase, acetohydroxy acid isomeroreductase, isopropylmalate isomerase and synthase along with leucine aminotransferase.
In the human body, it has been found to be a major component of buffer proteins, austacin, and ferritin.
- Leucine is exclusively ketogenic amino acid as it gives rise to ketoacyl CoA which is converted into acyl CoA derivatives which include HMG-CoA. This HMG-CoA is important as it takes part in the synthesis of cholesterol. It can also be broken down to acetoacetic acid and acetyl CoA.
- Leucine is essential in regulating blood glucose level as well as in the growth and repair of bones, skin, and muscles.
- It stimulates the synthesis of muscle proteins.
- It also results in the production of growth hormones and it also burns visceral fats which are located in the deeper layers of the body and are least responsive to dieting and exercises.
- Leucine also prevents the break down of muscle proteins which occurs during trauma, the stress of severe kind, during starvation or recovery from surgery.
- It is also useful for early wound healing.
- Patients suffering from phenylketonuria can take leucine which has been found beneficial to them.
– An excess intake of leucine results in the development of pellagra which is characterized by 3 D’s namely, Dermatitis, diarrhea, and death.
– Its high intake has also been found to damage the liver and kidney functions as a result of increased production of ammonia.
– A disease known as branched chain ketoaciduria or maple syrup urine disease has been found due to the failure of metabolism of three amino acids which are leucine, isoleucine, and valine. The failure occurs due to the deficiency of an enzyme branched chain keto acid dehydrogenase that is responsible for decarboxylation of these three amino acids. This disease is characterized by dehydration, vomiting, feeding problems in the baby and metabolic acidosis. There is a characteristic maple syrup odor in the urine, hence named maple syrup urine disease. If it is not treated, it will lead to mental retardation, physical disability, and even the death.
In a nutshell, leucine is an important amino acid. It is also available in the form of supplements in the market. These supplements can be taken with valine and isoleucine for better results.