Pyruvate Dehydrogenase Activity in Osmotically Shocked Rat Brain Mitochondria: Stimulation by Oxaloacetate

1. The effects of phenylpyruvate, a metabolite produced in phenylketonuria, on the pyruvate dehydrogenase-complex activity were investigated in rat brain mitochondria. 2. Pyruvate dehydrogenase activity was measured by two methods, one measuring the release of 14CO2 from [1-14C]pyruvate and the other measuring the acetyl-CoA formed by means of the coupling enzyme, pigeon liver arylamine acetyltransferase (EC 2.3.1.5). In neither case was there significant inhibition of the pyruvate dehydrogenase complex by phenylpyruvate at concentrations below 2mm. 3. However, phenylpyruvate acted as a classical competitive inhibitor of the coupling enzyme arylamine acetyltransferase, with a Ki of 100μm. 4. It was concluded that the inhibition of pyruvate dehydrogenase by phenylpyruvate is unlikely to be a primary enzyme defect in phenylketonuria.

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A comparison of the regulation of pyruvate dehydrogenase in mitochondria from rat brain and liver

Biochemical Journal ◽

10.1042/bj1500397 ◽

1975 ◽

Vol 150 (3) ◽

pp. 397-403 ◽

Cited By ~ 37

Author(s):

R Jope ◽

J P Blass

Keyword(s):

Rat Brain ◽

Dehydrogenase Activity ◽

Pyruvate Dehydrogenase ◽

Active Form ◽

Energy Charge ◽

Liver Mitochondria ◽

Brain Mitochondria ◽

Ruthenium Red ◽

Rat Brain And Liver ◽

Pyruvate Dehydrogenase Phosphatase

The total activity of pyruvate dehydrogenase in mitochondria isolated from rat brain and liver was 53.5 and 14.2nmol/min per mg of protein respectively. Pyruvate dehydrogenase in liver mitochondria incubated for 4 min at 37 degrees C with no additions was 30% in the active form and this activity increased with longer incubations until it was completely in the active form after 20 min. Brain mitochondrial pyruvate dehydrogenase activity was initially high and did not increase with addition of Mg2+ plus Ca2+ or partially purified pyruvate dehydrogenase phosphatase or with longer incubations. The proportion of pyruvate dehydrogenase in the active form in both brain and liver mitochondria changed inversely with changes in mitochondrial energy charge, whereas total pyruvate dehydrogenase did not change. The chelators citrate, isocitrate, EDTA, ethanedioxybis(ethylamine)tetra-acetic acid and Ruthenium Red each lowered pyruvate dehydrogenase activity in brain mitochondria, but only citrate and isocitrate did so in liver mitochondria. These chelators did not affect the energy charge of the mitochondria. Mg2+ plus Ca2+ reversed the pyruvate dehydrogenase inactivation in liver, but not brain, mitochondria. The regulation of the activation-inactivation of pyruvate dehydrogenase in mitochondria from rat brain and liver with respect to energy charge is similar and may be at least partially regulated by this parameter, and the effects of chelators differ in the two types of mitochondria.

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Development of mitochondrial energy metabolism in rat brain

Biochemical Journal ◽

10.1042/bj1640339 ◽

1977 ◽

Vol 164 (2) ◽

pp. 339-348 ◽

Cited By ~ 95

Author(s):

John M. Land ◽

Robert F. G. Booth ◽

Ruud Berger ◽

John B. Clark

Keyword(s):

Rat Brain ◽

Pyruvate Dehydrogenase ◽

Citrate Synthase ◽

Aerobic Glycolysis ◽

Biological Significance ◽

Brain Mitochondria ◽

Developmental Pattern ◽

Mitochondrial Energy Metabolism ◽

Rat Brain Mitochondria ◽

Total Brain

1. The development of pyruvate dehydrogenase and citrate synthase activity in rat brain mitochondria was studied. Whereas the citrate synthase activity starts to increase at about 8 days after birth, that of pyruvate dehydrogenase starts to increase at about 15 days. Measurements of the active proportion of pyruvate dehydrogenase during development were also made. 2. The ability of rat brain mitochondria to oxidize pyruvate follows a similar developmental pattern to that of the pyruvate dehydrogenase. However, the ability to oxidize 3-hydroxybutyrate shows a different developmental pattern (maximal at 20 days and declining by half in the adult), which is compatible with the developmental pattern of the ketone-body-utilizing enzymes. 3. The developmental pattern of both the soluble and the mitochondrially bound hexokinase of rat brain was studied. The total brain hexokinase activity increases markedly at about 15 days, which is mainly due to an increase in activity of the mitochondrially bound form, and reaches the adult situation (approx. 70% being mitochondrial) at about 30 days after birth. 4. The release of the mitochondrially bound hexokinase under different conditions by glucose 6-phosphate was studied. There was insignificant release of the bound hexokinase in media containing high KCl concentrations by glucose 6-phosphate, but in sucrose media half-maximal release of hexokinase was achieved by 70μm-glucose 6-phosphate 5. The production of glucose 6-phosphate by brain mitochondria in the presence of Mg2++glucose was demonstrated, together with the inhibition of this by atractyloside. 6. The results are discussed with respect to the possible biological significance of the similar developmental patterns of pyruvate dehydrogenase and the mitochondrially bound kinases, particularly hexokinase, in the brain. It is suggested that this association may be a mechanism for maintaining an efficient and active aerobic glycolysis which is necessary for full neural expression.

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The action of the local anaesthetic, benzyl alcohol and the monoamine oxidase inhibitor, clorgyline on the β-hydroxybutyrate dehydrogenase activity of adult and weanling rat brain mitochondria

Journal of Pharmacy and Pharmacology ◽

10.1111/j.2042-7158.1978.tb13370.x ◽

1978 ◽

Vol 30 (1) ◽

pp. 711-714 ◽

Cited By ~ 7

Author(s):

Miles D. Houslay ◽

Robert W. Palmer ◽

R. Julian S. Duncan

Keyword(s):

Monoamine Oxidase ◽

Rat Brain ◽

Benzyl Alcohol ◽

Dehydrogenase Activity ◽

Local Anaesthetic ◽

Monoamine Oxidase Inhibitor ◽

Brain Mitochondria ◽

Oxidase Inhibitor ◽

Rat Brain Mitochondria

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Comparative development of the pyruvate dehydrogenase complex and citrate synthase in rat brain mitochondria

Biochemical Journal ◽

10.1042/bj2380729 ◽

1986 ◽

Vol 238 (3) ◽

pp. 729-736 ◽

Cited By ~ 21

Author(s):

G D A Malloch ◽

L A Munday ◽

M S Olson ◽

J B Clark

Keyword(s):

Enzyme Activity ◽

Rat Brain ◽

Pyruvate Dehydrogenase ◽

Citrate Synthase ◽

Post Partum ◽

Pyruvate Dehydrogenase Complex ◽

Brain Mitochondria ◽

Rat Brain Mitochondria ◽

Developing Rat ◽

Dehydrogenase Complex

The enzyme activity of the pyruvate dehydrogenase complex (PDHC) was measured in mitochondria prepared from developing rat brain, before and after steady-state dephosphorylation of the E1 alpha subunit. A marked increase in dephosphorylated (fully activated) PDHC activity occurred between days 10 and 15 post partum, which represented approx. 60% of the difference in fully activated PDHC activity measured in foetal and adult rat brain mitochondria. There was no detectable change in the active proportion of the enzyme during mitochondrial preparation nor any qualitative alteration in the detectable catalytic and regulatory components of the complex, which might account for developmental changes in PDHC activity. The PDHC protein content of developing rat brain mitochondria and homogenates was measured by an enzyme-linked immunoadsorbent assay. The development of PDHC protein in both fractions agreed closely with the development of the PDHC activity. The results suggest that the developmental increase in PDHC activity is due to increased synthesis of PDHC protein, which is partly a consequence of an increase in mitochondrial numbers. However, the marked increase in PDHC activity measured between days 10 and 15 post partum is mainly due to an increase in the amount of PDHC per mitochondrion. The development of citrate synthase enzyme activity and protein was measured in rat brain homogenates and mitochondria. As only a small increase in citrate synthase activity and protein was detected in mitochondria between days 10 and 15 post partum, the marked increase in PDHC protein and enzyme activity may represent specific PDHC synthesis. As several indicators of acquired neurological competence become apparent during this period, it is proposed that preferential synthesis of PDHC may be crucial to this process. The results are discussed with respect to the possible roles played by PDHC in changes of respiratory-substrate utilization and the acquisition of neurological competence occurring during the development of the brain of a non-precocial species such as the rat.

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