Branched-chain amino acid

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A branched-chain amino acid (BCAA) is an amino acid having aliphatic side-chains with a branch (a central carbon atom bound to three or more carbon atoms). Among the proteinogenic amino acids, there are three BCAAs: leucine, isoleucine and valine.[1] Non-proteinogenic BCAAs include norvaline and 2-aminoisobutyric acid.

A chemical structure diagram of leucine
Leucine
A chemical structure diagram of isoleucine
Isoleucine
A chemical structure diagram of valine
Valine

The three proteinogenic BCAAs are among the nine essential amino acids for humans, accounting for 35% of the essential amino acids in muscle proteins and 40% of the preformed amino acids required by mammals.[2]

Research

Dietary BCAA supplementation has been used clinically to aid in the recovery of burn victims. A 2006 paper suggests that the concept of nutrition supplemented with all BCAAs for burns, trauma, and sepsis should be abandoned for a more promising leucine-only-supplemented nutrition that requires further evaluation. [3]

Dietary BCAAs have been used in an attempt to treat some cases of hepatic encephalopathy,[4] but BCAA provides no benefit for this condition.[5]

Cota et al.[6] demonstrated in 2006 that BCAAs, particularly leucine, also affect the mTOR pathway in rats, signaling two regions of their brains.

Degradation

Degradation of branched-chain amino acids involves the branched-chain alpha-keto acid dehydrogenase complex (BCKDH). A deficiency of this complex leads to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products in the blood and urine, giving the condition the name maple syrup urine disease.

The BCKDH complex converts branched-chain amino acids into Acyl-CoA derivatives, which after subsequent reactions are converted either into acetyl-CoA or succinyl-CoA that enter the citric acid cycle.[7]

Enzymes involved are branched chain aminotransferase and 3-methyl-2-oxobutanoate dehydrogenase.

BCAA pathway

See also

References

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  2. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Abstract on sciencemag.org
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.

Further reading

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External links

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