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

1987 ◽  
Vol 242 (3) ◽  
pp. 935-935
Keyword(s):  
Oxidative Decarboxylation ◽  
Acid Dehydrogenase ◽  
Branched Chain ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

scholarly journals Role of activation of myocardial branched-chain 2-oxo acid dehydrogenase complex in the regulation of leucine decarboxylation during cardiac work in vitro

1987 ◽  
Vol 248 (2) ◽  
pp. 423-428
Author(s):  
E Hildebrandt ◽  
M S Olson
Keyword(s):  
Flow Rate ◽  
Coronary Flow ◽  
Active Form ◽  
Oxidative Decarboxylation ◽  
Cardiac Work ◽  
Acid Dehydrogenase ◽  
Branched Chain ◽  
Langendorff Hearts ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

The oxidative decarboxylation of L-[1-14C]leucine was measured in the isolated perfused rat heart under both working and non-working conditions. Stimulation of decarboxylation of the labelled substrate was observed in working hearts as cardiac work was increased, and in Langendorff hearts upon increasing the coronary flow rate. The rate of L-[1-14C]leucine decarboxylation was significantly higher (P less than 0.05) in hearts working against moderate afterload pressure when compared to Langendorff hearts perfused at a matching coronary flow rate. The rate of release of 4-methyl-2-oxo[1-14C]pentanoate to the perfusate was high in Langendorff hearts, and was unaffected by changes in coronary flow. In contrast, perfusate levels of 14C-labelled 4-methyl-2-oxopentanoate decreased significantly upon the establishment of the working condition (P less than 0.05). These findings suggested an enhancement in the efficiency of the decarboxylation of the 2-oxo acid in response to cardiac work. The amount of branched-chain 2-oxo acid dehydrogenase complex present in the active form was measured in freeze-clamped hearts. Cardiac work resulted in a rapid activation of the complex (P less than 0.02) within 5 min of work when compared to control Langendorff hearts perfused at matching coronary flow rates. To a lesser extent, increasing the coronary flow rate in Langendorff-perfused hearts also led to activation of the enzyme complex. These studies suggest the following: a) L-leucine oxidation in myocardial tissue can be accelerated by exercise as it is in other tissues; b) this regulatory response can be evoked by the contractile activity of the heart itself, independent of contributions by circulating factors or nervous stimuli; and c) regulation of the activity state of the branched-chain 2-oxo acid dehydrogenase complex is involved in the mechanism by which metabolic flux through this pathway is controlled during cardiac work.

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 Dual role of a single multienzyme complex in the oxidative decarboxylation of pyruvate and branched-chain 2-oxo acids in Bacillus subtilis

1983 ◽  
Vol 215 (1) ◽  
pp. 133-140 ◽  
Author(s):  
P N Lowe ◽  
J A Hodgson ◽  
R N Perham
Keyword(s):  
Bacillus Subtilis ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Oxidative Decarboxylation ◽  
Multienzyme Complex ◽  
Complex Activity ◽  
Acid Dehydrogenase ◽  
Branched Chain ◽  
Acid Dehydrogenase Complex ◽  
Dehydrogenase Complex

The pyruvate dehydrogenase and branched-chain 2-oxo acid dehydrogenase activities of Bacillus subtilis were found to co-purify as a single multienzyme complex. Mutants of B. subtilis with defects in the pyruvate decarboxylase (E1) and dihydrolipoamide dehydrogenase (E3) components of the pyruvate dehydrogenase complex were correspondingly affected in branched-chain 2-oxo acid dehydrogenase complex activity. Selective inhibition of the E1 or lipoate acetyltransferase (E2) components in vitro led to parallel losses in pyruvate dehydrogenase and branched-chain 2-oxo acid dehydrogenase complex activity. The pyruvate dehydrogenase and branched-chain 2-oxo acid dehydrogenase complexes of B. subtilis at the very least share many structural components, and are probably one and the same. The E3 component appeared to be identical for the pyruvate dehydrogenase, 2-oxoglutarate dehydrogenase and branched-chain 2-oxo acid dehydrogenase complexes in this organism and to be the product of a single structural gene. Long-chain branched fatty acids are thought to be essential for maintaining membrane fluidity in B. subtilis, and it was observed that the ace (pyruvate dehydrogenase complex) mutant 61142 was unable rapidly to take up acetoacetate, unlike the wild-type, indicative of a defect in membrane permeability. A single pyruvate dehydrogenase and branched-chain 2-oxo acid dehydrogenase complex can be seen as an economical means of supplying two different sets of essential metabolites.

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
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