scholarly journals Phosphorylation of branched-chain 2-oxo acid dehydrogenase complex in isolated adipocytes. Effects of 2-oxo acids

1986 ◽  
Vol 236 (1) ◽  
pp. 209-213 ◽  
Author(s):  
S M A Jones ◽  
S J Yeaman
Keyword(s):  
Direct Evidence ◽  
Peptide Mapping ◽  
Polyacrylamide Gel Electrophoresis ◽  
Alpha Subunit ◽  
Intact Cells ◽  
Acid Dehydrogenase ◽  
Isolated Adipocytes ◽  
Branched Chain ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

Isolated adipocytes from rat epididymal fat-pads were incubated with [32P]Pi, and intracellular phosphoproteins were then analysed by SDS/polyacrylamide-gel electrophoresis and autoradiography. A phosphorylated polypeptide of apparent Mr 46,000 was identified as the alpha-subunit of branched-chain 2-oxo acid dehydrogenase complex by immunoprecipitation using antiserum raised against the homogeneous E1 component of branched-chain 2-oxo acid dehydrogenase complex. Immunoprecipitation of this phosphoprotein is blocked in a competitive manner by purified branched-chain 2-oxo acid dehydrogenase complex. Peptide mapping of the isolated phosphoprotein indicates that two sites on the polypeptide are phosphorylated in the intact cells. Addition of branched-chain 2-oxo acids to the incubation medium causes diminution in the extent of labelling of both phosphorylation sites on the alpha-subunit, an effect presumably mediated via their known inhibitory action on branched-chain 2-oxo acid dehydrogenase kinase. These observations provide direct evidence for phosphorylation of branched-chain 2-oxo acid dehydrogenase complex in intact cells.

scholarly journals Oxidative decarboxylation of 4-methylthio-2-oxobutyrate by branched-chain 2-oxo acid dehydrogenase complex

1986 ◽  
Vol 237 (2) ◽  
pp. 621-623 ◽  
Author(s):  
S M A Jones ◽  
S J Yeaman
Keyword(s):  
Pyruvate Dehydrogenase Complex ◽  
Oxidative Decarboxylation ◽  
Maximal Inhibition ◽  
Acid Dehydrogenase ◽  
Isolated Adipocytes ◽  
Oxoglutarate Dehydrogenase ◽  
Branched Chain ◽  
Kinase Phosphorylation ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

Highly purified branched-chain 2-oxo acid dehydrogenase complex (BCOADC) oxidizes 4-methylthio-2-oxobutyrate and 2-oxobutyrate, with Km values of 67 microM and 18 microM respectively. The Vmax. for oxidation of these substrates is 27% and 53% respectively of that for 3-methyl-2-oxobutyrate. Highly purified pyruvate dehydrogenase complex (PDC) oxidizes 2-oxobutyrate (Km 100 microM; Vmax. 49% of that for pyruvate) but not 4-methylthio-2-oxobutyrate, whereas 2-oxoglutarate dehydrogenase complex will not utilize either 2-oxo acid as substrate. BCOADC kinase is inhibited by both 4-methylthio-2-oxobutyrate and 2-oxobutyrate, with half-maximal inhibition by 45 microM and 50 microM respectively. Phosphorylation of BCOADC in isolated adipocytes is inhibited by both 4-methylthio-2-oxobutyrate and 2-oxobutyrate, consistent with their inhibitory action of BCOADC kinase. Phosphorylation of PDC is decreased by 2-oxobutyrate, but not by 4-methylthio-2-oxobutyrate.

scholarly journals Hepatic Branched-Chain .ALPHA.-Keto Acid Dehydrogenase Complex in Female Rats: Activation by Exercise and Starvation.

1999 ◽  
Vol 45 (3) ◽  
pp. 303-309 ◽  
Author(s):  
Rumi KOBAYASHI ◽  
Yoshiharu SHIMOMURA ◽  
Taro MURAKAMI ◽  
Naoya NAKAI ◽  
Megumi OTSUKA ◽  
...  
Keyword(s):  
Female Rats ◽  
Keto Acid ◽  
Acid Dehydrogenase ◽  
Branched Chain ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

scholarly journals Effects of clofibric acid on the activity and activity state of the hepatic branched-chain 2-oxo acid dehydrogenase complex

1992 ◽  
Vol 285 (1) ◽  
pp. 167-172 ◽  
Author(s):  
Y Zhao ◽  
J Jaskiewicz ◽  
R A Harris
Keyword(s):  
Active Form ◽  
Clofibric Acid ◽  
Chow Diet ◽  
Acid Dehydrogenase ◽  
Low Protein ◽  
Activity State ◽  
Branched Chain ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

Feeding clofibric acid to rats caused little or no change in total activity of the liver branched-chain 2-oxo acid dehydrogenase complex (BCODC). No change in mass of liver BCODC was detected by immunoblot analysis in response to dietary clofibric acid. No changes in abundance of mRNAs for the BCODC E1 alpha, E1 beta and E2 subunits were detected by Northern-blot analysis. Likewise, dietary clofibric acid had no effect on the activity state of liver BCODC (percentage of enzyme in the dephosphorylated, active, form) of rats fed on a chow diet. However, dietary clofibric acid greatly increased the activity state of liver BCODC of rats fed on a diet deficient in protein. No stable change in liver BCODC kinase activity was found in response to clofibric acid in either chow-fed or low-protein-fed rats. Clofibric acid had a biphasic effect on flux through BCODC in hepatocytes prepared from low-protein-fed rats. Stimulation of BCODC flux at low concentrations was due to clofibric acid inhibition of BCODC kinase, which in turn allowed activation of BCODC by BCODC phosphatase. Inhibition of BCODC flux at high concentrations was due to direct inhibition of BCODC by clofibric acid. The results suggest that the effects of clofibric acid in vivo on branched-chain amino acid metabolism can be explained by the inhibitory effects of this drug on BCODC kinase.

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