QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) An erratum has been published Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Hutson, S. M. Articles by LaNoue, K. F. Search for Related Content PubMed PubMed Citation Articles by Hutson, S. M. Articles by LaNoue, K. F.

---

4th Amino Acid Assessment Workshop

Branched-Chain Amino Acid Metabolism: Implications for Establishing Safe Intakes^1,2

Department of Biochemistry and Molecular Biology, Wake Forest University School of Medicine, Winston-Salem, NC 27157 and ^* Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA 17033

³To whom correspondence should be addressed. E-mail: shutson{at}wfubmc.edu.

There are several features of the metabolism of the indispensable BCAAs that set them apart from other indispensable amino acids. BCAA catabolism involves 2 initial enzymatic steps that are common to all 3 BCAAs; therefore, the dietary intake of an individual BCAA impacts on the catabolism of all 3. The first step is reversible transamination followed by irreversible oxidative decarboxylation of the branched-chain -keto acid transamination products, the branched chain -keto acids (BCKAs). The BCAA catabolic enzymes are distributed widely in body tissues and, with the exception of the nervous system, all reactions occur in the mitochondria of the cell. Transamination provides a mechanism for dispersing BCAA nitrogen according to the tissue’s requirements for glutamate and other dispensable amino acids. The intracellular compartmentalization of the branched-chain aminotransferase isozymes (mitochondrial branched-chain aminotransferase, cytosolic branched-chain aminotransferase) impacts on intra- and interorgan exchange of BCAA metabolites, nitrogen cycling, and net nitrogen transfer. BCAAs play an important role in brain neurotransmitter synthesis. Moreover, a dysregulation of the BCAA catabolic pathways that leads to excess BCAAs and their derivatives (e.g., BCKAs) results in neural dysfunction. The relatively low activity of catabolic enzymes in primates relative to the rat may make the human more susceptible to excess BCAA intake. It is hypothesized that the symptoms of excess intake would mimic the neurological symptoms of hereditary diseases of BCAA metabolism.

KEY WORDS: • branched-chain aminotransferases • nitrogen cycles • glutamate • alanine • mitochondria

This article has been cited by other articles:

				M. Hiroyama, T. Aoyagi, Y. Fujiwara, S. Oshikawa, A. Sanbe, F. Endo, and A. Tanoue Hyperammonaemia in V1a vasopressin receptor knockout mice caused by the promoted proteolysis and reduced intrahepatic blood volume J. Physiol., June 15, 2007; 581(3): 1183 - 1192. [Abstract] [Full Text] [PDF]

				L. Cynober and R. A. Harris Symposium on Branched-Chain Amino Acids: Conference Summary J. Nutr., January 1, 2006; 136(1): 333S - 336S. [Full Text] [PDF]