Project: Research project

Project Details


The overall objective is to establish the mechanisms responsible for the
regulation of the oxidation of branched-chain amino acids by mammalian
cells. Studies will be conducted with purified branched-chain
Alpha-ketoacid dehydrogenase (BCKDH) complex, purified BCKDH kinase,
purified BCKDH phosphatase, isolated hepatocytes, isolated myocytes,
perfused rat heart, isolated liver and heart mitochondria, and intact
animals. The working hypothesis is that covalent modification by
phosphorylation-dephosphorylation is an important mechanism for regulation
of BCKDH. Studies will be conducted to further characterize the BCKDH
complex purified in this laboratory from rabbit liver, to isolate and
characterize the phosphatase responsible for dephosphorylation and
activation of BCKDH to further investigate with intact animals the effects
of various nutritional and hormonal states as well as specific drugs on the
activity and phosphorylation state of BCKDH in various tissues, and finally
to determine with isolated hepatocytes, myocytes, and mitochondria whether
the phosphorylation state of the BCKDH is subject to acute hormonal
control. The detailed specific aims include to establish (a) molecular
weight and subunit organization of BCKDH; (b) the number and amino acid
sequences of the phosphorylation sites in the 47,000 Mr Alpha-subunit; (c)
the effectiveness of various Alpha-chloro- and Alpha-ketoacids as
inhibitors of BCKDH kinase; (d) the role of Ca++ as an inhibitor of BCKDH
kinase; (e) the effects of fasting, obesity, diabetes, and protein
deprivation on the phosphorylation state of BCKDH in liver, heart, muscle,
kidney, and adipose tissue; and (f) whether the phosphorylation state of
BCKDH is subject to hormonal control. These studies should help explain
altered branched-chaim amino acid metabolism known to occur in numerous
diseases and metabolic conditions, including diabetes, obesity, maple syrup
urine disease, phenylketonuria, kwashiorkor, and cancer.
Effective start/end date7/1/786/30/88


  • National Institutes of Health


  • Medicine(all)


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