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Novel mechanism responsible for regulation of branched‐chain alpha‐ketoacid dehydrogenase kinase
Author(s) -
Shimomura Yoshiharu,
Kondo Yusuke,
Ito Rina,
Tsuji Ai,
Shibata Katsumi,
Kitaura Yasuyuki
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.909.3
Subject(s) - catabolism , dephosphorylation , leucine , amino acid , phosphorylation , valine , kinase , dehydrogenase , biochemistry , isoleucine , mitochondrion , phosphatase , chemistry , biology , enzyme
Branched‐chain amino acids (BCAAs: leucine, isoleucine, and valine) are indispensable amino acids. The BCAA catabolism is regulated by branched‐chain alpha‐ketoacid dehydrogenase (BCKDH), which is located at the second step of the mitochondrial catabolic pathway. The BCKDH is regulated by a phosphorylation‐dephosphorylation cycle, and BCKDH kinase (BDK) is responsible for inactivation of the BCKDH by phosphorylation of the E1‐alpha component. It has been demonstrated that two forms of BDK exist in rat liver mitochondria: a form bound to BCKDH and a free form. Only the bound form is suggested to be active. In the present study, we found a BDK‐inactivating factor in mitochondrial extracts from rat liver. The BDK‐inactivating factor was separated from the BCKDH‐BDK complex by high‐speed centrifugation and both are reconstitutable. We here report the characteristics of the BDK‐inactivating factor, which released the BDK from the BCKDH in a Ca ion‐dependent manner. From these findings, we propose the novel mechanism responsible for the regulation of BCAA catabolism. Support or Funding Information Funding for this research was in part received from the AJINOMOTO AMINO ACID RESEARCH PROGRAM.