Effect of dietary protein on the liver content and subunit composition of the branched-chain alpha-ketoacid dehydrogenase complex

Arch Biochem Biophys. 1994 Feb 1;308(2):446-53. doi: 10.1006/abbi.1994.1063.


Levels of expression of two subunits of the liver branched-chain alpha-ketoacid dehydrogenase complex in response to extremes of dietary protein intake (50% versus 0% protein diet) were determined by quantitative immunoblotting. Dietary protein deficiency decreased the amount of E1 alpha protein to a greater extent than E2 protein. The ratio of E1 alpha to E2 was below 1 in the liver of animals starved for protein and above 1 in the liver of animals fed the high-protein diet. Supplementation of the 0% protein diet with 5% leucine (but not 5% valine) had the same effect as the 50% protein diet. The extremes of dietary protein also resulted in a divergent pattern of expression of the mRNAs for the subunits of the complex. The E1 beta message showed the expected corollary of being greater in the liver of the high-protein-fed rats than the no-protein-fed rats. In contrast, the E2 message was not affected by the two extremes of dietary protein and the E1 alpha message was greater in the liver of the no-protein-fed rats than the high-protein-fed rats. Thus, coordinate regulation of gene expression of the subunits of the complex does not occur in response to dietary protein. Post-transcriptional regulatory mechanisms most likely determine the amount of the complex and the ratio of its subunits. The decrease in E1 alpha/E2 protein ratio that occurs in dietary protein deficiency may increase sensitivity of the complex to phosphorylation-mediated inhibition by branched-chain alpha-ketoacid dehydrogenase kinase.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
  • Animals
  • Blotting, Northern
  • Blotting, Western
  • Dietary Proteins* / pharmacology
  • Ketone Oxidoreductases / biosynthesis
  • Ketone Oxidoreductases / isolation & purification
  • Ketone Oxidoreductases / metabolism*
  • Liver / enzymology*
  • Macromolecular Substances
  • Male
  • Mitochondria, Liver / enzymology
  • Multienzyme Complexes / biosynthesis
  • Multienzyme Complexes / isolation & purification
  • Multienzyme Complexes / metabolism*
  • Protein-Energy Malnutrition / enzymology
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Wistar
  • Time Factors


  • Dietary Proteins
  • Macromolecular Substances
  • Multienzyme Complexes
  • RNA, Messenger
  • Ketone Oxidoreductases
  • 3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)