scholarly journals Regulation of pyruvate dehydrogenase kinase activity from pig kidney cortex

1992 ◽  
Vol 288 (2) ◽  
pp. 369-373 ◽  
Author(s):  
T Pawelczyk ◽  
M S Olson
Keyword(s):  
Ionic Strength ◽  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Kinase ◽  
Kidney Cortex ◽  
Small Range ◽  
High Concentration ◽  
Optimum Activity ◽  
Pig Kidney

The activity of pyruvate dehydrogenase (PDH) kinase in the purified PDH complex from pig kidney is sensitive to changes in ionic strength. The enzyme has optimum activity within a small range of ionic strength (0.03-0.05 M). An increase in ionic strength from 0.04 M to 0.2 M lowers the activity of PDH kinase by 32% and decreases the Km for ATP from 25 microM to 10 microM. At constant ionic strength (0.15 M) the enzyme has optimum activity over a broad pH range (7.2-8.0). The PDH kinase is stimulated 2.2-fold by 20 mM-K+, whereas Na+ even at high concentration (80 mM) has no effect on the enzyme activity. The stimulation of PDH kinase by K+ is not dependent on pH and ionic strength. PDH kinase is inhibited by HPO4(2-) in the presence of K+, whereas HPO4(2-) has no effect on the activity of this enzyme in the absence of K+. HPO4(2-) at concentrations of 2 and 10 mM inhibits PDH kinase by 28% and 55% respectively. The magnitude of this inhibition is not dependent on the ATP/ADP ratio. Inhibition by HPO4(2-) in the concentration range 0-10 mM is non-competitive with respect to ATP, and becomes mixed-type at concentrations over 10 mM. The Ki for HPO4(2-) is 10 mM. When HPO4(2-) is replaced by SO4(2-), the same effects on the activity of PDH kinase are observed. PDH kinase is also inhibited by Cl-. In the presence of 80 mM-Cl- the PDH kinase is inhibited by 40%. The inhibition by Cl- is not dependent on K+. In conclusion, we postulate that changes in phosphate concentrations may play a significant role in the regulation of PDH kinase activity in vivo.

scholarly journals The effects of various anions and cations on the regulation of pyruvate dehydrogenase complex activity from pig kidney cortex

1988 ◽  
Vol 253 (3) ◽  
pp. 819-825 ◽  
Author(s):  
T Pawelczyk ◽  
R A Easom ◽  
M S Olson
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Maximal Activity ◽  
Hill Coefficient ◽  
Kidney Cortex ◽  
Complex Activity ◽  
Pig Kidney ◽  
Constant Strength ◽  
Dehydrogenase Complex

The activity of pyruvate dehydrogenase complex (PDC) purified from pig kidney cortex was found to be affected by various uni- and bi-valent ions. At a constant strength of 0.13 M at pH 7.8, K+, Na+, Cl-, HCO3- and HPO4(2-) had significant effects on the activity of PDC: Na+, K+ and HPO4(2-) stimulated, but HCO3- and Cl- inhibited. The stimulatory effect of Na+ was mediated by a change in the Vmax. of PDC only, whereas K+ produced an increase in Vmax. and a change in the Hill coefficient (h). The extent of stimulation produced by HPO4(2-)4 on the activity of PDC was dependent on the concentrations of K+ and Na+. Both cations at concentrations higher than 40 mM partially prevented the effect of HPO4(2-)4. Cl- and HCO3- anions decreased the Vmax. of the enzyme and increased the S0.5 for pyruvate. The effects of Na+, K+, Cl-, HPO4(2-) and HCO3- on the activity of PDC were additive. In the presence of 80 mM-K+, 20 mM-Na+, 10 mM-HPO4(2-), 20 mM-Cl- and 20 mM-HCO3- the activity of PDC was increased by 30%, the S0.5 for pyruvate was increased from 75 to 158 microM and h was decreased from 1.3 to 1.1. Under these conditions and at 1.0 mM-pyruvate, the activity of PDC was 80% of the maximal activity achieved in the presence of these ions and 4.5 mM-pyruvate. The present study suggests that PDC may operate under non-saturating concentrations for substrate in vivo.

scholarly journals Comparison of the kinetic properties of the pyruvate dehydrogenase complex from pig kidney cortex and medulla.

1993 ◽  
Vol 40 (3) ◽  
pp. 411-419 ◽  
Author(s):  
T Pawełczyk ◽  
M S Olson
Keyword(s):  
Ionic Strength ◽  
Pyruvate Dehydrogenase ◽  
Pyruvate Dehydrogenase Complex ◽  
Product Inhibition ◽  
Hill Coefficient ◽  
Kidney Cortex ◽  
Kinetic Properties ◽  
Kidney Medulla ◽  
Pig Kidney ◽  
Dehydrogenase Complex

The activity of the pyruvate dehydrogenase complex (PDC) purified from pig kidney medulla was affected by K+, Na+, Cl-, HCO3-, HPO4(2-) and changes in ionic strength. Increased ionic strength influenced the activity of PDC from medulla by decreasing the Vmax and S0.5 for pyruvate and increasing the Hill coefficient. The magnitude of these changes was smaller than the corresponding changes for PDC purified from the cortex. In the presence of K+ (80 mM), Na+ (20 mM), Cl- (20 mM), HCO3- (20 mM), HPO4(2-) (10 mM) and at ionic strength of 0.15 M the S0.5 for pyruvate of PDC from medulla was 117 microM and the enzyme complex was saturated by 1.1 mM pyruvate. Under these conditions the S0.5 for pyruvate of PDC derived from cortex was 159 microM and the enzyme was saturated at 4.5 mM pyruvate. Based on the results presented in this report it is suggested that PDC in kidney medulla may be regulated not only by a phosphorylation/dephosphorylation system and end-product inhibition but also via changes in ionic strength.

Increased hepatic pyruvate dehydrogenase kinase activity in fed hyperthyroid rats: studies in vivo and with cultured hepatocytes

1996 ◽  
Vol 119 (2) ◽  
pp. 219-224 ◽  
Author(s):  
Mary C. Sugden ◽  
Lee G.D. Fryer ◽  
David A. Priestman ◽  
Karen A. Orfali ◽  
Mark J. Holness
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Kinase ◽  
Cultured Hepatocytes

scholarly journals Inhibition of lactate glucogneogenesis in rat kidney by dichloroacetate

1978 ◽  
Vol 170 (3) ◽  
pp. 551-560 ◽  
Author(s):  
J H Lacey ◽  
P J Randle
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Rat Kidney ◽  
Active Form ◽  
Glucose Production ◽  
Inhibitory Effect ◽  
Diabetic Rats ◽  
Pyruvate Dehydrogenase Kinase ◽  
No Oxidation ◽  
Kidney Cortex

1. Sodium dichloroacetate (1mM) inhibited glucose production from L-lactate in kidney-cortex slices from fed, starved or alloxan-diabetic rates. In general gluconeogenesis from other substrates was no inhibited. 2. Sodium dichloracetate inhibited glucose production from L-lactate but no from pyruvate in perfused isolated kidneys from normal or alloxan-diabetic rats. 3. Sodium dichloroacetate is an inhibitor of the pyruvate dehydrogenase kinase reaction and it effected conversion of pyruvate dehydrogenase into its its active (dephosphorylated) form in kidney in vivo. In general, pyruvate dehydrogenase was mainly in the active form in kidneys perfused or incubated with L-lactate and the inhibitory effect of dichloroacetate on glucose production was not dependent on activation of pyruvate dehydrogenase. 4. Balance data from kidney slices showed that dichloroacetate inhibits lactate uptake, glucose and pyruvate production from lactate, but no oxidation of lactate. 5. The mechanism of this effect of dichloroactetate on glucose production from lactate has not been fully defined, but evidence suggests that it may involve a fall in tissue pyruvate concentration and inhibition of pyruvate carboxylation.

scholarly journals Regulation of heart muscle pyruvate dehydrogenase kinase

1974 ◽  
Vol 143 (3) ◽  
pp. 625-641 ◽  
Author(s):  
Ronald H. Cooper ◽  
Philip J. Randle ◽  
Richard M. Denton
Keyword(s):  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Close Correlation ◽  
Pyruvate Dehydrogenase Kinase ◽  
Sodium Pyrophosphate ◽  
Kinase Assay ◽  
High Concentration ◽  
Kinase Reaction ◽  
Dehydrogenase Reaction ◽  
Thiamin Pyrophosphate

1. The activity of pig heart pyruvate dehydrogenase kinase was assayed by the incorporation of [32P]phosphate from [γ-32P]ATP into the dehydrogenase complex. There was a very close correlation between this incorporation and the loss of pyruvate dehydrogenase activity with all preparations studied. 2. Nucleoside triphosphates other than ATP (at 100μm) and cyclic 3′:5′-nucleotides (at 10μm) had no significant effect on kinase activity. 3. The Km for thiamin pyrophosphate in the pyruvate dehydrogenase reaction was 0.76μm. Sodium pyrophosphate, adenylyl imidodiphosphate, ADP and GTP were competitive inhibitors against thiamin pyrophosphate in the dehydrogenase reaction. 4. The Km for ATP of the intrinsic kinase assayed in three preparations of pig heart pyruvate dehydrogenase was in the range 13.9–25.4μm. Inhibition by ADP and adenylyl imidodiphosphate was predominantly competitive, but there was nevertheless a definite non-competitive element. Thiamin pyrophosphate and sodium pyrophosphate were uncompetitive inhibitors against ATP. It is suggested that ADP and adenylyl imidodiphosphate inhibit the kinase mainly by binding to the ATP site and that the adenosine moiety may be involved in this binding. It is suggested that thiamin pyrophosphate, sodium pyrophosphate, adenylyl imidodiphosphate and ADP may inhibit the kinase by binding through pyrophosphate or imidodiphosphate moieties at some site other than the ATP site. It is not known whether this is the coenzyme-binding site in the pyruvate dehydrogenase reaction. 5. The Km for pyruvate in the pyruvate dehydrogenase reaction was 35.5μm. 2-Oxobutyrate and 3-hydroxypyruvate but not glyoxylate were also substrates; all three compounds inhibited pyruvate oxidation. 6. In preparations of pig heart pyruvate dehydrogenase free of thiamin pyrophosphate, pyruvate inhibited the kinase reaction at all concentrations in the range 25–500μm. The inhibition was uncompetitive. In the presence of thiamin pyrophosphate (endogenous or added at 2 or 10μm) the kinase activity was enhanced by low concentrations of pyruvate (25–100μm) and inhibited by a high concentration (500μm). Activation of the kinase reaction was not seen when sodium pyrophosphate was substituted for thiamin pyrophosphate. 7. Under the conditions of the kinase assay, pig heart pyruvate dehydrogenase forms 14CO2 from [1-14C]pyruvate in the presence of thiamin pyrophosphate. Previous work suggests that the products may include acetoin. Acetoin activated the kinase reaction in the presence of thiamin pyrophosphate but not with sodium pyrophosphate. It is suggested that acetoin formation may contribute to activation of the kinase reaction by low pyruvate concentrations in the presence of thiamin pyrophosphate. 8. Pyruvate effected the conversion of pyruvate dehydrogenase phosphate into pyruvate dehydrogenase in rat heart mitochondria incubated with 5mm-2-oxoglutarate and 0.5mm-l-malate as respiratory substrates. It is suggested that this effect of pyruvate is due to inhibition of the pyruvate dehydrogenase kinase reaction in the mitochondrion. 9. Pyruvate dehydrogenase kinase activity was inhibited by high concentrations of Mg2+ (15mm) and by Ca2+ (10nm–10μm) at low Mg2+ (0.15mm) but not at high Mg2+ (15mm).

scholarly journals Fate of glutamate carbon and nitrogen in isolated guinea-pig kidney-cortex tubules. Evidence for involvement of glutamate dehydrogenase in glutamine sythesis from glutamate

1980 ◽  
Vol 188 (3) ◽  
pp. 873-880 ◽  
Author(s):  
G Baverel ◽  
C Genoux ◽  
M Forissier ◽  
M Pellet
Keyword(s):  
Guinea Pig ◽  
Glutamate Dehydrogenase ◽  
Carbon Skeleton ◽  
Kidney Cortex ◽  
Glutamate Metabolism ◽  
Carbon And Nitrogen ◽  
Pig Kidney ◽  
Glutamate Concentration ◽  
Rate Limiting Step

1. The pathways and the fate of glutamate carbon and nitrogen were investigated in isolated guinea-pig kidney-cortex tubules. 2. At low glutamate concentration (1 mM), the glutamate carbon skeleton was either completely oxidized or converted into glutamine. At high glutamate concentration (5 mM), glucose, lactate and alanine were additional products of glutamate metabolism. 3. At neither concentration of glutamate was there accumulation of ammonia. 4. Nitrogen-balance calculations and the release of 14CO2 from L-[1-14C]glutamate (which gives an estimation of the flux of glutamate carbon skeleton through alpha-oxoglutarate dehydrogenase) clearly indicated that, despite the absence of ammonia accumulation, glutamate metabolism was initiated by the action of glutamate dehydrogenase and not by transamination reactions as suggested by Klahr, Schoolwerth & Bourgoignie [(1972) Am. J. Physiol. 222, 813-820] and Preuss [(1972) Am. J. Physiol. 222, 1395-1397]. Additional evidence for this was obtained by the use of (i) amino-oxyacetate, an inhibitor of transaminases, which did not decrease glutamate removal, or (ii) L-methionine DL-sulphoximine, an inhibitor of glutamine synthetase, which caused an accumulation of ammonia from glutamate. 5. Addition of NH4Cl plus glutamate caused an increase in both glutamate removal and glutamine synthesis, demonstrating that the supply of ammonia via glutamate dehydrogenase is the rate-limiting step in glutamine formation from glutamate. NH4Cl also inhibited the flux of glutamate through glutamate dehydrogenase and the formation of glucose, alanine and lactate. 6. The activities of enzymes possibly involved in the glutamate conversion into pyruvate were measured in guinea-pig renal cortex. 7. Renal arteriovenous-difference measurements revealed that in vivo the guinea-pig kidney adds glutamine and alanine to the circulating blood.

scholarly journals Studies of the long-term regulation of hepatic pyruvate dehydrogenase kinase

1998 ◽  
Vol 329 (1) ◽  
pp. 89-94 ◽  
Author(s):  
C. Mary SUGDEN ◽  
G. D. Lee FRYER ◽  
A. Karen ORFALI ◽  
A. David PRIESTMAN ◽  
Elaine DONALD ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Pyruvate Dehydrogenase ◽  
Unsaturated Fatty Acids ◽  
Fold Increase ◽  
Membrane Lipid ◽  
Dietary Lipid ◽  
Pyruvate Dehydrogenase Kinase ◽  
Plasma Insulin Concentration

The administration of a low-carbohydrate/high-saturated-fat (LC/HF) diet for 28 days or starvation for 48 h both increased pyruvate dehydrogenase kinase (PDHK) activity in extracts of rat hepatic mitochondria, by approx. 2.1-fold and 3.5-fold respectively. ELISAs of extracts of hepatic mitochondria, conducted over a range of pyruvate dehydrogenase (PDH) activities, revealed that mitochondrial immunoreactive PDHKII (the major PDHK isoform in rat liver) was significantly increased by approx. 1.4-fold after 28 days of LC/HF feeding and by approx. 2-fold after 48 h of starvation. The effect of LC/HF feeding to increase hepatic PDHK activity was retained through hepatocyte preparation, but was decreased on 21 h culture with insulin (100μ-i.u./ml). A sustained (24 h) 2-4-fold elevation in plasma insulin concentration in vivo (achieved by insulin infusion via an osmotic pump) suppressed the effect of LC/HF feeding so that hepatic PDHK activities did not differ significantly from those of (insulin-infused) control rats. The increase in hepatic PDHK activity evoked by 28 days of LC/HF feeding was prevented and reversed (within 24 h) by the replacement of 7% of the dietary lipid with long-chain ω-3 fatty acids. Analysis of hepatic membrane lipid revealed a 1.9-fold increase in the ratio of total polyunsaturated ω-3 fatty acids to total mono-unsaturated fatty acids. The results indicate that the increased hepatic PDHK activities observed in livers of LC/HF-fed or 48 h-starved rats are associated with long-term actions to increase hepatic PDHKII concentrations. The long-term regulation of hepatic PDHK by LC/HF feeding might be achieved through an impaired action of insulin to suppress PDHK activity. In addition, the fatty acid composition of the diet, rather than the fat content, is a key influence.

Increased pyruvate dehydrogenase kinase activity in response to sepsis

1991 ◽  
Vol 260 (5) ◽  
pp. E669-E674 ◽  
Author(s):  
T. C. Vary
Keyword(s):  
Skeletal Muscle ◽  
Pyruvate Dehydrogenase ◽  
Kinase Activity ◽  
Pyruvate Dehydrogenase Complex ◽  
Pyruvate Dehydrogenase Kinase ◽  
Sterile Inflammation ◽  
Stable Factor ◽  
Skeletal Muscle Mitochondria ◽  
Dependent Inactivation ◽  
Significant Difference

The effect of sterile inflammation and sepsis on the proportion of active pyruvate dehydrogenase complex (PDH) in mitochondria isolated from skeletal muscle has been investigated. The proportion of active PDH in mitochondria isolated from septic animals was significantly reduced compared with control under all incubation conditions examined, even in the presence of inhibitors of the PDH kinase. There was no significant difference between control and sterile inflammation in any of the incubations examined. The rate constant for ATP-dependent inactivation of the PDH complex in mitochondrial extracts from control animals was -0.42 min-1 (r = 0.993; P less than 0.001) and was not altered in mitochondrial extracts from sterile inflammatory animals (-0.43 min-1; r = 0.999; P less than 0.001). However, rate constants for inactivation in septic animals was significantly increased over twofold to -1.08 min-1 (r = 0.987; P less than 0.001) (P less than 0.001 vs. control or sterile inflammation). In the presence of inhibitors of the PDH kinase reaction (2.5 mM pyruvate or 1 mM dichloroacetate), inactivation of PDH after addition of ATP was significantly greater in mitochondrial extracts from septic than either control or sterile inflammatory animals. These results suggest that sepsis, but not sterile inflammation, induces a stable factor in skeletal muscle mitochondria that increased PDH kinase activity.

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