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Published on: May 3, 2012
Ca
Seisuke Noguchi1, Yusuke Kondo1, Rina Ito1
1Laboratory of Nutritional Biochemistry, Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, 464-8601, Japan.
Abstract:
Catabolism of the branched-chain amino acids (BCAAs: leucine, isoleucine, and valine) is regulated by the branched-chain α-ketoacid dehydrogenase (BCKDH) complex, which in turn is regulated by phosphorylation catalyzed by BCKDH kinase (BDK). Thiamine pyrophosphate (TPP) is required as a coenzyme for the E1 component of the BCKDH complex and can also bring about activation of the complex by inhibiting BDK. The present study shows that free Ca2+ in the physiological range greatly increases the sensitivity of BDK to inhibition by TPP (IC50 of 2.5 μM in the presence of 1 μM free Ca2+). This novel mechanism may be responsible for the stimulation of BCAA oxidation by conditions that increase mitochondrial free Ca2+ levels, e.g. in skeletal muscle during exercise.
