UMMS Affiliation

Department of Physiology

Publication Date

2-15-1989

Document Type

Article

Subjects

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); Adenosine Triphosphate; Adipose Tissue; Animals; Enzyme Activation; Insulin; Ketone Oxidoreductases; Leucine; Male; Mitochondria; Multienzyme Complexes; Phosphorylation; Proteins; Pyruvate Dehydrogenase (Lipoamide); Pyruvate Dehydrogenase Complex; Rats

Disciplines

Physiology

Abstract

The activity of the intramitochondrial branched-chain 2-oxo acid dehydrogenase (BCDH), like that of pyruvate dehydrogenase, is regulated, at least in part, by interconversion between the active dephosphorylated enzyme and its inactive phosphorylated form. The stimulatory effect of insulin on BCDH activity was compared with its effect on phosphorylation of the enzyme. Intact tissues were incubated in the presence or the absence of insulin, and then mitochondria were isolated and disrupted before assaying for enzyme activity or estimating the extent of enzyme phosphorylation. Tissues were incubated in either the presence or the absence of leucine, which also stimulated BCDH activity up to 10-fold. Insulin (1 munit/ml) doubled the activity of BCDH in the absence and in the presence of leucine. Together, 1 mM-leucine and insulin appeared to stimulate BCDH activity fully. Phosphorylation of BCDH was estimated indirectly by measuring the incorporation of 32P into phosphorylation sites that remained unesterified after preparing mitochondrial extracts under conditions that preserved the effect of insulin on BCDH activity. Increased incorporation of 32P in these experiments implies decreased phosphorylation in situ when tissues were incubated with insulin and leucine. In the absence of leucine, little incorporation of 32P into BCDH was detected. In the presence of leucine, however, incorporation of 32P into BCDH was markedly increased, and insulin increased 32P incorporation still further. The results support the hypothesis that leucine and insulin both stimulate the activity of BCDH by promoting its dephosphorylation.

Rights and Permissions

Citation: Biochem J. 1989 Feb 15;258(1):229-35.

Related Resources

Link to article in PubMed

Journal/Book/Conference Title

The Biochemical journal

PubMed ID

2649086

Included in

Physiology Commons

Share

COinS
 
 

To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.