Computer simulation of metabolism in pyruvate-perfused rat heart. III. Pyruvate dehydrogenase

1979 ◽  
Vol 237 (3) ◽  
pp. R167-R173 ◽  
Author(s):  
M. C. Kohn ◽  
M. J. Achs ◽  
D. Garfinkel
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Pyruvate Dehydrogenase Complex ◽  
Active Form ◽  
Realistic Model ◽  
Specific Protein ◽  
Active Species ◽  
Perfused Rat Heart ◽  
Synergistic Activation ◽  
The Difference

A physiologically and biochemically realistic model of the regulation of pyruvate dehydrogenase complex (PDH) was constructed for the perfused rat heart. It includes conversion between inactive (phospho) and active (dephospho) forms by a specific protein kinase (PDHK) and phosphoprotein phosphatase (PDHP). The activity of the tightly bound PDHK is influenced by synergistic activation/inhibition by acetyl CoA/CoASH and NADH/NAD. PDHK in this simulation was more sensitive to the fraction of ADP that was Mg2+-chelated than to the ATP-to-ADP ratio. Ca2+ stimulates binding of Mg2+-dependent PDHP to the complex; the bound enzyme was considered to be the active species. The fraction of PDH in the active form, rather than substrate and inhibitor levels, determines PDH activity under these conditions. This fraction depends on the present value and recent history of the difference between PDHK and PDHP activities. Both of these are active continuously and continuously control PDH.

scholarly journals Pyruvate dehydrogenase kinase/activator in rat heart mitochondria, Assay, effect of starvation, and effect of protein-synthesis inhibitors of starvation

1982 ◽  
Vol 206 (1) ◽  
pp. 103-111 ◽  
Author(s):  
A L Kerbey ◽  
P J Randle
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
High Speed ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Complex ◽  
Active Form ◽  
Pyruvate Dehydrogenase Kinase ◽  
Heart Mitochondria ◽  
Supernatant Fraction ◽  
Kidney Mitochondria

Purified pig heart pyruvate dehydrogenase complex is denuded of its intrinsic pyruvate dehydrogenase kinase activity by sedimentation from dilute solution (60 munits/ml). Kinase activity is restored by a supernatant fraction prepared by high-speed centrifugation of rat heart mitochondrial extracts; the factor responsible is referred to as kinase/activator. Kinase/activator was also assayed by its ability to accelerate NgATP-induced inactivation in dilute solutions of unprocessed complex (50 munits/ml). With this assay it has been shown that the activity of kinase/activator in heart mitochondria is increased 3-6 fold by starvation of rats for 48 h. This increase was prevented completely by cycloheximide treatment and prevented partially by puromycin treatment of rats during starvation. The concentration of kinase/activator in heart mitochondria fell during 20 h of re-feeding of 48 h-starved rats; this fall was correlated with an increase in the proportion of complex in the active form. Kinase/activator was also extracted from ox kidney mitochondria, and on gel filtration (Sephadex G-100, superfine grade) was eluted close to the void volume. Kinase/activator (ox kidney or rat heart) was thermolabile, non-diffusable on dialysis, and inactivated by trypsin. The results of this study appear to show increased cytoplasmic synthesis in starvation of pyruvate dehydrogenase kinase and/or of an activator of the kinase.

Regulation of pyruvate dehydrogenase complex in ischemic rat heart

1984 ◽  
Vol 246 (6) ◽  
pp. H858-H864 ◽  
Author(s):  
T. B. Patel ◽  
M. S. Olson
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Pyruvate Dehydrogenase Complex ◽  
Total Activity ◽  
Control Flow ◽  
Enzyme Complex ◽  
Multienzyme Complex ◽  
Flow Rates ◽  
Perfused Rat Heart ◽  
Dehydrogenase Complex

The effect of flow-induced ischemia on the rate of pyruvate decarboxylation and the activation state of the pyruvate dehydrogenase multienzyme complex was investigated in the isolated, perfused rat heart. Pyruvate dehydrogenase activity in the heart decreased significantly during flow-induced ischemia and was a function of changes in the activation state (i.e., active/total activity) of the enzyme complex. In the absence of pyruvate, the activation state of pyruvate dehydrogenase decreased from nearly 100% active at the normal flow rate (10 ml/min) to 20% active as the flow was reduced to 0.5 ml/min. At high pyruvate levels (5 mM), the activation state increased from nearly 70% active at control flow rates to 100% active during ischemia. At an intermediate pyruvate concentration (0.5 mM), the enzyme complex was maintained at a relatively low activation state (30–35% active) throughout the range of flow rates tested. Ischemia caused elevated perfusate lactate concentrations only when the flow rates were less than 5.0 ml/min. The activation state of the pyruvate dehydrogenase complex in hearts perfused with glucose was also decreased during ischemia.

Effects of aging on the activities of pyruvate dehydrogenase complex and its kinase in rat heart

Life Sciences ◽  
1997 ◽  
Vol 60 (25) ◽  
pp. 2309-2314 ◽  
Author(s):  
Naoya Nakai ◽  
Yuzo Sato ◽  
Yoshiharu Oshida ◽  
Atsushi Yoshimura ◽  
Noriaki Fujitsuka ◽  
...  
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Pyruvate Dehydrogenase Complex ◽  
Effects Of Aging ◽  
Dehydrogenase Complex

scholarly journals Conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active complex by the phosphate reaction in heart mitochondria is inhibited by alloxan-diabetes or starvation in the rat

1978 ◽  
Vol 173 (2) ◽  
pp. 669-680 ◽  
Author(s):  
N J Hutson ◽  
A L Kerbey ◽  
P J Randle ◽  
P H Sugden
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Pyruvate Dehydrogenase Complex ◽  
Diabetic Rats ◽  
Atp Depletion ◽  
Heart Mitochondria ◽  
Active Complex ◽  
Phosphate Complex ◽  
Rat Hearts ◽  
Dehydrogenase Complex

1. The conversion of inactive (phosphorylated) pyruvate dehydrogenase complex into active (dephosphorylated) complex by pyruvate dehydrogenase phosphate phosphatase is inhibited in heart mitochondria prepared from alloxan-diabetic or 48h-starved rats, in mitochondria prepared from acetate-perfused rat hearts and in mitochondria prepared from normal rat hearts incubated with respiratory substrates for 6 min (as compared with 1 min). 2. This conclusion is based on experiments with isolated intact mitochondria in which the pyruvate dehydrogenase kinase reaction was inhibited by pyruvate or ATP depletion (by using oligomycin and carbonyl cyanide m-chlorophenylhydrazone), and in experiments in which the rate of conversion of inactive complex into active complex by the phosphatase was measured in extracts of mitochondria. The inhibition of the phosphatase reaction was seen with constant concentrations of Ca2+ and Mg2+ (activators of the phosphatase). The phosphatase reaction in these mitochondrial extracts was not inhibited when an excess of exogenous pig heart pyruvate dehydrogenase phosphate was used as substrate. It is concluded that this inhibition is due to some factor(s) associated with the substrate (pyruvate dehydrogenase phosphate complex) and not to inhibition of the phosphatase as such. 3. This conclusion was verified by isolating pyruvate dehydrogenase phosphate complex, free of phosphatase, from hearts of control and diabetic rats an from heart mitochondria incubed for 1min (control) or 6min with respiratory substrates. The rates of re-activation of the inactive complexes were then measured with preparations of ox heart or rat heart phosphatase. The rates were lower (relative to controls) with inactive complex from hearts of diabetic rats or from heart mitochondria incubated for 6min with respiratory substrates. 4. The incorporation of 32Pi into inactive complex took 6min to complete in rat heart mitocondria. The extent of incorporation was consistent with three or four sites of phosphorylation in rat heart pyruvate dehydrogenase complex. 5. It is suggested that phosphorylation of sites additional to an inactivating site may inhibit the conversion of inactive complex into active complex by the phosphatase in heart mitochondria from alloxan-diabetic or 48h-starved rats or in mitochondria incubated for 6min with respiratory substrates.

scholarly journals The activity of the pyruvate dehydrogenase complex in heart and liver from mice during the development of obesity and insulin resistance

1987 ◽  
Vol 243 (2) ◽  
pp. 549-553 ◽  
Author(s):  
I D Caterson ◽  
L D Astbury ◽  
P F Williams ◽  
M A Vanner ◽  
G J Cooney ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Pyruvate Dehydrogenase ◽  
Serum Insulin ◽  
Pyruvate Dehydrogenase Complex ◽  
Active Form ◽  
Whole Body ◽  
Acid Oxidation ◽  
Mitochondrial Fatty Acid Oxidation ◽  
Gold Thioglucose ◽  
Mitochondrial Fatty Acid

The amount of pyruvate dehydrogenase in the active form (PDHa) was increased 1.7-fold compared with controls in heart muscle of mice 1 week after induction of obesity with a single injection of gold-thioglucose. At 4 weeks post injection, the amount of PDHa was decreased to 32% of control, a value which was observed in later stages of the obesity syndrome. In contrast, liver PDHa was increased and remained at an increased activity during the development of obesity. Despite normal post-prandial serum insulin contents, liver membrane insulin-receptor numbers were decreased 1 week after gold-thioglucose injection, and there was no change in receptor affinity. The decrease in heart PDHa in the obese animals was reversed by a single dose of 2-tetradecylglycidic acid, but this inhibitor of mitochondrial fatty acid oxidation did not affect liver PDHa in these animals. These early and diverse changes in PDHa argue for a multifactorial aetiology in the development of the whole-body insulin resistance seen in older gold-thioglucose-treated obese animals.

scholarly journals Time courses of the responses of pyruvate dehydrogenase activities to short-term starvation in diaphragm and selected skeletal muscles of the rat

1989 ◽  
Vol 264 (3) ◽  
pp. 771-776 ◽  
Author(s):  
M J Holness ◽  
Y L Liu ◽  
M C Sugden
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Skeletal Muscles ◽  
Pyruvate Dehydrogenase Complex ◽  
Active Form ◽  
Oxidative Capacity ◽  
Short Term ◽  
Fed State ◽  
Time Courses ◽  
Adductor Longus ◽  
Selection Of

In the fed state, the percentages of the pyruvate dehydrogenase complex (PDH) in the active form (PDHa) in diaphragm and a selection of skeletal muscles (adductor longus, soleus, extensor digitorum longus, tibialis anterior, gastrocnemius) ranged from 8% (soleus) to 38% (gastrocnemius). Major decreases in PDHa activities in all of these muscles were observed after 15 h of starvation, by which time activities were less than 40% of the fed values. In general, the response to starvation was observed more rapidly in muscles of high oxidative capacity. The patterns of changes in skeletal-muscle PDH activities during the fed-to-starved transition are discussed in relation to changes in lipid-fuel supply and oxidation.

scholarly journals Regulation of pyruvate dehydrogenase in rat heart. Mechanism of regulation of proportions of dephosphorylated and phosphorylated enzyme by oxidation of fatty acids and ketone bodies and of effects of diabetes: role of coenzyme A, acetyl-coenzyme A and reduced and oxidized nicotinamide-adenine dinucleotide

1976 ◽  
Vol 154 (2) ◽  
pp. 327-348 ◽  
Author(s):  
A L. Kerbey ◽  
P J. Randle ◽  
R H. Cooper ◽  
S Whitehouse ◽  
H T. Pask ◽  
...  
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Heart ◽  
Alloxan Diabetes ◽  
Total Activity ◽  
Diabetic Rats ◽  
Pyruvate Dehydrogenase Kinase ◽  
Perfused Rat Heart ◽  
Kinase Reaction ◽  
The Matrix ◽  
Rat Heart Mitochondria

The proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart was decreased by alloxan-diabetes or by perfusion with media containing acetate, n-octanoate or palmitate. The total activity of the dehydrogenase was unchanged. 2. Pyruvate (5 or 25mM) or dichloroacetate (1mM) increased the proportion of active (dephosphorylated) pyruvate dehydrogenase in perfused rat heart, presumably by inhibiting the pyruvate dehydrogenase kinase reaction. Alloxan-diabetes markedly decreased the proportion of active dehydrogenase in hearts perfused with pyruvate or dichloroacetate. 3. The total activity of pyruvate dehydrogenase in mitochondria prepared from rat heart was unchanged by diabetes. Incubation of mitochondria with 2-oxo-glutarate plus malate increased ATP and NADH concentrations and decreased the proportion of active pyruvate dehydrogenase. The decrease in active dehydrogenase was somewhat greater in mitochondria prepared from hearts of diabetic rats than in those from hearts of non-diabetic rats. Pyruvate (0.1-10 mM) or dichloroacetate (4-50 muM) increased the proportion of active dehydrogenase in isolated mitochondria presumably by inhibition of the pyruvate dehydrogenase kinase reaction. They were much less effective in mitochondria from the hearts of diabetic rats than in those of non-diabetic rats. 4. The matrix water space was increased in preparations of mitochondria from hearts of diabetic rats. Dichloroacetate was concentrated in the matrix water of mitochondria of non-diabetic rats (approx. 16-fold at 10 muM); mitochondria from hearts of diabetic rats concentrated dichloroacetate less effectively. 5. The pyruvate dehydrogenase phosphate phosphatase activity of rat hearts and of rat heart mitochondria (approx. 1-2 munit/unit of pyruvate dehydrogenase) was not affected by diabetes. 6. The rate of oxidation of [1-14C]pyruvate by rat heart mitochondria (6.85 nmol/min per mg of protein with 50 muM-pyruvate) was approx. 46% of the Vmax. value of extracted pyruvate dehydrogenase (active form). Palmitoyl-L-carnitine, which increased the ratio of [acetyl-CoA]/[CoA] 16-fold, inhibited oxidation of pyruvate by about 90% without changing the proportion of active pyruvate dehydrogenase.

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