Valine (Essential amino acid).
Valine is an essential amino acid classified as nonpolar. It is named after the plant valerian. Valine is used in the biosynthesis of proteins. It is essential in humans, meaning the body cannot synthesize it and must be obtained from the diet. Like leucine and isoleucine, valine is a branched-chain amino acid.
Branched chain amino acids (BCAA) are essential amino acids whose carbon structure is marked by a branch point. These three amino acids (Leucine, Isoleucine, and valine) are critical to human life and are particularly involved in stress, energy and muscle metabolism.
Despite their structural similarities, the branched amino acids have different metabolic routes, with valine going solely to carbohydrates, leucine solely to fats and isoleucine to both. The different metabolism accounts for different requirements for these essential amino acids in humans.
Valine is an aliphatic and extremely hydrophobic essential amino acid. It is found in many proteins, mostly in the interior of globular proteins helping to determine three-dimensional structure. A glycogenic amino acid, valine maintains mental vigor, muscle coordination, and emotional calm. Valine supplements are used for muscle growth, tissue repair, and energy.
Promotes muscle growth and tissue repair.
L-valine is a branched-chain essential amino acid that has stimulant activity. It promotes muscle growth and tissue repair. It is a precursor in the penicillin biosynthetic pathway.
Valine appears to promote glycogen synthesis in muscle cells, but to a lesser degree (about 61% as potent) as leucine supplementation.
BCAA are decreased in patients with liver disease, such as hepatitis, hepatic coma, cirrhosis, extrahepatic biliary atresia or portacaval shunt. Aromatic amino acids (AAA) tyrosine, tryptophan and phenylalanine, as well as methionine are increased in these conditions. Valine in particular, has been established as a useful supplemental therapy to the ailing liver.
Diary is a good source of valine.
Human dietary sources are foods that contain protein, such as meats, dairy products, soy products, beans and legumes.
Deficiency is marked by neurological defects.
Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors.
Maple syrup urine disease (MSUD) is caused by the inability to metabolize branched chain amino acids leucine, isoleucine, and valine. The disease is so named because urine from affected people smells like maple syrup.
A deficiency of valine may also affect the myelin covering of the nerves, and cause degenerative neurological conditions.
All the branched chain amino acids (BCAA) including valine probably compete with aromatic amino acids (AAA) for absorption into the brain. Supplemental BCAA with vitamin B6 and zinc help normalize the BCAA:AAA ratio.
Many types of inborn errors of BCAA metabolism exist, and are marked by various abnormalities. The most common form is the maple syrup urine disease, marked by a characteristic urinary odor. Other abnormalities are associated with a wide range of symptoms, such as mental retardation, ataxia, hypoglycemia, spinal muscle atrophy, rash, vomiting and excessive muscle movement.
In sickle-cell disease, valine substitutes for the hydrophilic amino acid glutamic acid in hemoglobin. Because valine is hydrophobic, the hemoglobin does not fold correctly. Hypervalinemia is another example of an inborn error of metabolism involving Valine.
Most forms of BCAA metabolism errors are corrected by dietary restriction of BCAA and at least one form is correctable by supplementation with 10 mg of biotin daily.
The requirements for BCAAs are; valine 12 mg/kg, leucine 14 mg/kg and isoleucine 16 mg/kg of body weight respectively.