Effects of Diabetes on the Activity and Content of the Branched-Chain α-Ketoacid Dehydrogenase Complex in Liver

R. Gibson, Z. Yu, J. Jaskiewicz, S. E. Fineberg, Robert Harris

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Abstract

Severe ketotic diabetes induced in rats by streptozotocin resulted in a reduction in activity of the hepatic branched-chain α-ketoacid dehydrogenase complex, regardless of whether activity was expressed on the basis of liver wet weight, total liver, liver protein, or liver DNA. A decrease in enzyme specific activity (units of enzyme activity per mg of enzyme protein) was found responsible for the reduction in measurable enzyme activity of the complex. Insulin treatment reversed the decrease in enzyme specific activity. Treatment of tissue extracts with phosphoprotein phosphatase had no effect, indicating that activity of the complex was decreased by some mechanism other than reversible phosphorylation. Specific protein components of the complex were also not found reduced by the diabetic state. Induction of severe ketotic diabetes in rats previously fed a low-protein diet resulted in activation of the enzyme as a cortsequence of dephosphorylation. Nevertheless, the specific activity of the dephosphorylated enzyme of diabetic, low-protein-fed rats was decreased relative to that of control, low-protein-fed animals. Reconstitution studies with tissue extracts fortified with the purified E1 component indicate that severe diabetes induces a defect in this component of the hepatic branched-chain α-ketoacid dehydrogenase complex.

Original languageEnglish
Pages (from-to)22-28
Number of pages7
JournalArchives of Biochemistry and Biophysics
Volume306
Issue number1
DOIs
StatePublished - Oct 1993

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3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)
Medical problems
Liver
Enzymes
Tissue Extracts
Enzyme activity
Proteins
Rats
Phosphorylation
Phosphoprotein Phosphatases
Nutrition
Streptozocin
Protein-Restricted Diet
Enzyme Activation
Animals
Chemical activation
Insulin
Defects
DNA
Weights and Measures

ASJC Scopus subject areas

  • Molecular Biology
  • Biophysics
  • Biochemistry

Cite this

Effects of Diabetes on the Activity and Content of the Branched-Chain α-Ketoacid Dehydrogenase Complex in Liver. / Gibson, R.; Yu, Z.; Jaskiewicz, J.; Fineberg, S. E.; Harris, Robert.

In: Archives of Biochemistry and Biophysics, Vol. 306, No. 1, 10.1993, p. 22-28.

Research output: Contribution to journalArticle

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