Branched-chain amino acid
A branched-chain amino acid (BCAA) is an amino acid having aliphatic side-chains with a branch (a carbon atom bound to more than two other carbon atoms). Among the proteinogenic amino acids, there are three BCAAs: leucine, isoleucine and valine.[1]
The 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] BCAA’s have been used clinically to aid in the recovery of burn victims.[3] They are also used in the treatment in some cases of hepatic encephalopathy.[4]
A recent study suggested that the reduction in blood BCAAs may be associated with the improvement in blood sugar regulation. The mechanism remains unknown.[5]
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 acid (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.[6]
Enzymes involved are branched chain aminotransferase and 3-methyl-2-oxobutanoate dehydrogenase.
See also
References
- ^ Sowers, Strakie. "A Primer On Branched Chain Amino Acids". Huntington College of Health Sciences. http://www.hchs.edu/literature/BCAA.pdf. Retrieved 22 March 2011.
- ^ "Exercise Promotes BCAA Catabolism: Effects of BCAA Supplementation on Skeletal Muscle during Exercise". J. Nutr. 134 (6): 1583S-1587S. 2004. http://jn.nutrition.org/content/134/6/1583S.full. Retrieved 22 March 2011.
- ^ "Therapeutic use of branched-chain amino acids in burn, trauma, and sepsis". J. Nutr.. 1 Suppl 136 (30): 8S-13S. 2006. http://jn.nutrition.org/content/136/1/308S.short. Retrieved 22 March 2011.
- ^ "Nutrition in hepatic encephalopathy". Nutr Clin Pract. 25 (3): 257–64. 2010. doi:10.1177/0884533610368712. http://ncp.sagepub.com/content/25/3/257.abstract.
- ^ "Differential Metabolic Impact of Gastric Bypass Surgery Versus Dietary Intervention in Obese Diabetic Subjects Despite Identical Weight Loss". Sci Transl Med 3 (80re2). 2011. http://stm.sciencemag.org/content/3/80/80re2. Retrieved 27 April 2011.
- ^ "Mechanisms of human insulin resistance and thiazolidinedione-mediated insulin sensitization". Proc. Nat. Acad. Sci. USA 106 (44): 18745–18750. 2009. doi:10.1073/pnas.0903032106. http://www.pnas.org/content/106/44/18745.full. Retrieved 22 March 2011.
Further reading
- Karlsson HK, Nilsson PA, Nilsson J, Chibalin AV, Zierath JR, Blomstrand E (2004). "Branched-chain amino acids increase p70S6k phosphorylation in human skeletal muscle after resistance exercise". Am. J. Physiol. Endocrinol. Metab. 287 (1): E1–7. doi:10.1152/ajpendo.00430.2003. PMID 14998784.
- Blomstrand E, Eliasson J, Karlsson HK, Köhnke R (2006). "Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise". J. Nutr. 136 (1 Suppl): 269S–73S. PMID 16365096.
- Norton LE, Layman DK (2006). "Leucine regulates translation initiation of protein synthesis in skeletal muscle after exercise". J. Nutr. 136 (2): 533S–537S. PMID 16424142.
External links
|
|
|
Cellulose and sucrose
metabolism
Starch and glycogen
metabolism
Aspartate amino acid
group synthesis
Porphyrins and
corrinoids
metabolism
Glutamate amino
acid group
synthesis
|
All pathway labels on this image are links, simply click to access the article. |
|
A high resolution labeled version of this image is available here. |
|
|
|
|
|
|
| By properties |
|
|
|
|
|
|
|
|
|
Polar, uncharged
|
|
|
|
Positive charge (pKa)
|
|
|
|
Negative charge (pKa)
|
|
|
|
General
|
|
|
|
| Other classifications |
|
|
biochemical families: prot · nucl · carb (glpr, alco, glys) · lipd (fata/i, phld, strd, gllp, eico) · amac/i · ncbs/i · ttpy/i
|
|