Showing papers on "Pyruvate dehydrogenase kinase published in 1977"
TL;DR: The data indicate that the two enzymes are similar to pyruvate synthase and alpha-ketoglutarate synthase, respectively, and the involvement of the described oxidoreductases in cell carbon synthesis is discussed.
Abstract: Cell-free extracts of Methanobacterium thermoautotrophicum were found to contain high activities of the following oxidoreductases (at 60°C): pyruvate dehydrogenase (coenzyme A acetylating), 275 nmol/min per mg of protein; α-ketoglutarate dehydrogenase (coenzyme A acylating), 100 nmol/min per mg; fumarate reductase, 360 nmol/min per mg; malate dehydrogenase, 240 nmol/min per mg; and glyceraldehyde-3-phosphate dehydrogenase, 100 nmol/min per mg. The kinetic properties (apparent Vmax and KM values), pH optimum, temperature dependence of the rate, and specificity for electron acceptors/donors of the different oxidoreductases were examined. Pyruvate dehydrogenase and α-ketoglutarate dehydrogenase were shown to be two separate enzymes specific for factor 420 rather than for nicotinamide adenine dinucleotide (NAD), NADP, or ferredoxin as the electron acceptor. Both activities catalyzed the reduction of methyl viologen with the respective α-ketoacid and a coenzyme A-dependent exchange between the carboxyl group of the α-ketoacid and CO2. The data indicate that the two enzymes are similar to pyruvate synthase and α-ketoglutarate synthase, respectively. Fumarate reductase was found in the soluble cell fraction. This enzyme activity coupled with reduced benzyl viologen as the electron donor, but reduced factor 420, NADH, or NADPH was not effective. The cells did not contain menaquinone, thus excluding this compound as the physiological electron donor for fumarate reduction. NAD was the preferred coenzyme for malate dehydrogenase, whereas NADP was preferred for glyceraldehyde-3-phosphate dehydrogenase. The organism also possessed a factor 420-dependent hydrogenase and a factor 420-linked NADP reductase. The involvement of the described oxidoreductases in cell carbon synthesis is discussed.
241 citations
TL;DR: The reaction of 5'-p-fluorosulfonylbenzoyladenosine with pyruvate kinase exhibits several of the characteristics of affinity labeling of the enzyme, consistent with the postulate that lysyl or tyrosyl residues are the most probably candidates for the critical amino acids.
Abstract: Rabbit muscle pyruvate kinase is irreversibly inactivated upon incubation with the adenine nucleotide analogue, 5'-p-fluorosulfonylbenzoyladenosine. A plot of the time dependence of the logarithm of the enzymatic activity at a given time divided by the initial enzymatic activity(logE/Eo) reveals a biphasic rate of inactivation, which is consistent with a rapid reaction to form partially active enzyme having 54% of the original activity, followed by a slower reaction to yield totally inert enzyme. In addition to the pyruvate kinase activity of the enzyme, modification with 5'-p-fluorosulfonylbenzoyladenosine also disrupts its ability to catalyze the decarboxylation of oxaloacetate and the ATP-dependent enolization of pyruvate. In correspondence with the time dependence of inactivation, the rate of incorporation of 5'-p-[14C]fluorosulfonylbenzoyladenosine is also biphasic. Two moles of reagent per mole of enzyme subunit are bound when the enzyme is completely inactive. The pseudo-first-order rate constant for the rapid rate is linearly dependent on reagent concentration, whereas the constant for the slow rate exhibits saturation kinetics, suggesting that the reagent binds reversibly to the second site prior to modification. The adenosine moiety is essential for the effectiveness of 5'-p-fluorosulfonylbenzoyladenosine, since p-fluorosulfonylbenzoic acid does not inactivate pyruvate kinase at a significant rate. Thus, the reaction of 5'-p-fluorosulfonylbenzoyladenosine with pyruvate kinase exhibits several of the characteristics of affinity labeling of the enzyme. Protection against inactivation by 5'-p-fluorosulfonylbenzoyladenosine is provided by the addition to the incubation mixture of phosphoenolpyruvate. Mg-ADP or Mg2+. In contrast, the addition of pyruvate, Mg-ATP, or ADP and ATP alone has no effect on the rate of inactivation. These observations are consistent with the postulate that the 5'-p-fluorosulfonylbenzoyladenosine specifically labels amino acid residues in the binding region of Mg2+ and the phosphoryl group of phosphoenolpyruvate which is transferred during the catalytic reaction. The rate of inactivation increases with increasing pH, and k1 depends on the unprotonated form of an amino acid residue with pK = 8.5. On the basis of the pH dependence of the reaction of pyruvate kinase with 5'-p-fluorosulfonylbenzoyladenosine and the elimination of cysteine residues as possible sites of reaction, it is postulated that lysyl or tyrosyl residues are the most probably candidates for the critical amino acids.
127 citations
TL;DR: The pyruvate dehydrogenase complex from pea (Pisum sativum L.) mitochondria was purified 23-fold by high speed centrifugation and glycerol gradient fractionation and activity was found to be coincident with the proplastid peak on all of the gradients.
Abstract: The pyruvate dehydrogenase complex from pea ( Pisum sativum L) mitochondria was purified 23-fold by high speed centrifugation and glycerol gradient fractionation The complex had a s 20, w of 475S but this is a minimal value since the complex is unstable The complex is specific for NAD + and pyruvate; NADP + and other keto acids give no reaction Mg 2+ , thiamine pyrophosphate, and cysteine are also required for maximal activity The pH optimum for the complex was between 65 and 75 Continuous sucrose density gradients were used to separate castor bean ( Ricinus communis L) endosperm proplastids from mitochondria Pyruvate dehydrogenase complex activity was found to be coincident with the proplastid peak on all of the gradients Some separation of proplastids and mitochondria could be achieved by differential centrifugation and the ratios of the activities of the pyruvate dehydrogenase complex to succinic dehydrogenase and acetyl-CoA carboxylase to succinic dehydrogenase were consistent with both the pyruvate dehydrogenase complex and acetyl-CoA carboxylase being present in the proplastid The proplastid fraction has to be treated with a detergent, Triton X-100, before maximal activity of the pyruvate dehydrogenase complex activity is expressed, indicating that it is bound in the organelle The complex had a sharp pH optimum of 75 The complex required added Mg 2+ , cysteine, and thiamine pyrophosphate for maximal activity but thiamine pyrophosphate was inhibitory at higher concentrations
121 citations
TL;DR: 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 in the brain.
Abstract: 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 70mum-glucose 6-phosphate 5 The production of glucose 6-phosphate by brain mitochondria in the presence of Mg(2+)+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
121 citations
TL;DR: The much lower ratios required for enhanced inactivation of the complex by pyruvate dehydrogenase kinase than for product inhibition indicate that the level of activity of the regulatory enzyme is not directly determined by the relative affinity of substrates and products of catalytic sites in the pyruVate dehydrogensase complex.
103 citations
TL;DR: Comparison between mitochondria from hearts of diabetic and non-diabetic rats shows that phosphorylation and inactivation of pyruvate dehydrogenase is enhanced in alloxan-diabetes by some factor other than concentration ratios of ATP/ADP, NADH/NAD+ or acetyl-CoA/CoA.
Abstract: 1. The proportion of active (dephosphorylated) pyruvate dehydrogenase in rat heart mitochondria was correlated with total concentration ratios of ATP/ADP, NADH/NAD+ and acetyl-CoA/CoA. These metabolites were measured with ATP-dependent and NADH-dependent luciferases. 2. Increase in the concentration ratio of NADH/NAD+ at constant [ATP]/[ADP] and [acetyl-CoA]/[CoA] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between mitochondria incubated with 0.4mM- or 1mM-succinate and mitochondria incubated with 0.4mM-succinate+/-rotenone. 3. Increase in the concentration ratio acetyl-CoA/CoA at constant [ATP]/[ADP] and [NADH][NAD+] was associated with increased phosphorylation and inactivation of pyruvate dehydrogenase. This was based on comparison between incubations in 50 micrometer-palmitotoyl-L-carnitine and in 250 micrometer-2-oxoglutarate +50 micrometer-L-malate. 4. These findings are consistent with activation of the pyruvate dehydrogenase kinase reaction by high ratios of [NADH]/[NAD+] and of [acetyl-CoA]/[CoA]. 5. Comparison between mitochondria from hearts of diabetic and non-diabetic rats shows that phosphorylation and inactivation of pyruvate dehydrogenase is enhanced in alloxan-diabetes by some factor other than concentration ratios of ATP/ADP, NADH/NAD+ or acetyl-CoA/CoA.
98 citations
TL;DR: Results indicate that pyruvate carboxylase is in fact a lipogenic enzyme, and that the activities of enzymes less directly related to lipogenesis rise only 3–5-fold while other unrelated enzymes do not increase significantly.
96 citations
95 citations
TL;DR: The dihydrolipoyl transacetylase component of the Escherichia coli pyruvate dehydrogenase complex appears to comprise an interacting network that functions as an acyl group and electron pair relay system through thiol-disulfide and acyl-transfer reactions among all of the lipoyl moieties.
Abstract: The dihydrolipoyl transacetylase component of the Escherichia coli pyruvate dehydrogenase complex [pyruvate:lipoate oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1] bears two sites on each of its 24 polypeptide chains that undergo reductive acetylation by [2-14C]pyruvate and thiamin pyrophosphate, acetylation by [1-14C]acetyl-CoA in the presence of DPNH, and reaction with N-ethyl[2,3-14C]maleimide in the presence of pyruvate and thiamin pyrophosphate. The data strongly imply that these sites are covalently bound lipoyl moieties. The results of similar experiments with the E. coli α-ketoglutarate dehydrogenase complex [2-oxoglutarate:lipoate oxidoreductase (decarboxylating and acceptor-succinylating), EC 1.2.4.2] indicate that its dihydrolipoyl transsuccinylase component bears only one lipoyl moiety on each of its 24 chains. Charging of the 48 acetyl acceptor sites on the transacetylase or the 24 succinyl acceptor sites on the transsuccinylase by pyruvate or α-ketoglutarate, respectively, and thiamin pyrophosphate was observed in the presence of only a few functionally active pyruvate dehydrogenase or α-ketoglutarate dehydrogenase chains. Extensive crosslinking of the transacetylase chains was observed when the pyruvate dehydrogenase complex was treated with pyruvate and thiamin pyrophosphate or with DPNH in the presence of N,N′-o- or N,N′-p-phenylenedimaleimide, respectively. When the α-ketoglutarate dehydrogenase complex was treated with DPNH in the presence of N,N′-p-phenylenedimaleimide, only transsuccinylase monomers and crosslinked transsuccinylase dimers were detected. It appears that the 48 lipoyl moieties in the transacetylase and the 24 lipoyl moieties in the transsuccinylase comprise an interacting network that functions as an acyl group and electron pair relay system through thiol-disulfide and acyl-transfer reactions among all of the lipoyl moieties.
86 citations
TL;DR: In this paper, the presence of a pyruvate(-)-OH(-) exchange transporter which supplies the mitochondrion with oxidizable substrate was found in animal mitochondria, and malate and NADH were inhibited by alpha-cyano-4-hydroxy-cinnamic acid.
Abstract: Pyruvate oxidation and swelling in pyruvate solutions by corn (Zea mays) mitochondria were inhibited by alpha-cyano-4-hydroxy-cinnamic acid, an inhibitor of pyruvate transport in animal mitochondria; however, there was no inhibition of pyruvate dehydrogenase activity, and malate and NADH oxidation were not affected. These results suggest the presence of a pyruvate(-)-OH(-) exchange transporter which supplies the mitochondrion with oxidizable substrate. Lactate appears to be transported also, but not dicarboxylate anions or inorganic phosphate. The rate of pyruvate transport was much slower than that of malate, however, and valinomycin was required to elicit appreciable swelling in potassium pyruvate.Malate oxidation contributed significantly to respiration supported by pyruvate plus malate, and malate did not act solely as a "sparker" for pyruvate oxidation. NAD(+)-malic enzyme activity was found in sonicated preparations, and comparison of O(2) consumption with CO(2) released from 1-(14)C-pyruvate indicated that transported malate was being converted to pyruvate, particularly as the malate to pyruvate ratio increased. The results suggest that pyruvate transport becomes limiting under conditions of high energy demand, but that rapid malate transport makes up the difference, supplying pyruvate via malic enzyme and replenishing losses of tricarboxylic acid cycle intermediates.
83 citations
TL;DR: Results show that P8 is glyceraldehyde-3-phosphate dehydrogenase, a value comparable to that of the crystalline enzyme from several sources.
Abstract: The DNA-binding protein P8 from transformed hamster fibroblasts (line NIL-1-hamster sarcoma virus) has been purified to homogeneity by DNA-cellulose and phosphocellulose chromatography. The molecular weight of dissociated P8 is 36000, the same as that reported for the subunits of glyceraldehyde-3-phosphate dehydrogenase, and the mobility of these proteins in polyacrylamide gels is identical. The amino acid composition of P8 is very similar to that of glyceraldehyde-3-phosphate dehydrogenase. When assayed for glyceraldehyde-3-phosphate dehydrogenase activity the P8 preparation had a specific activity of 54.6 units/mg, a value comparable to that of the crystalline enzyme from several sources. Furthermore, serum prepared against P8 crossreacts with glyceraldehyde-3-phosphate dehydrogenase from hamster muscle. These results show that P8 is glyceraldehyde-3-phosphate dehydrogenase. The interaction of P8 from transformed fibroblasts and glyceraldehyde-3-phosphate dehydrogenase from hamster and rabbit muscle with DNA has been studied using a Millipore filtration technique. These proteins have affinity for single-stranded DNA but not for double-stranded DNA.
01 Jan 1977
TL;DR: The results suggest that pyruvate transport becomes limiting under conditions of high energy demand, but that rapid malate transport makes up the difference, supplying pyruVate via malic enzyme and replenishing losses of tricarboxylic acid cycle intermediates.
Abstract: Pyruvate oxidation and swelling in pyruvate solutions by corn (Zea mays) mitochondria were inhibited by a-cyano-4-hydroxy-cinnamic acid, an inhibitor of pyruvate transport in animal mitochondria; however, there was no inhibition of pyruvate dehydrogenase activity, and malate and NADH oxidation were not affected. These results suggest the presence of a pyruvate--OH- exchange transporter which supplies the mitochondrion with oxidizable substrate. Lactate appears to be transported also, but not dicarboxylate anions or inorganic phosphate. The rate of pyruvate transport was much slower than that of malate, however, and valinomycin was required to elicit appreciable swelling in potassium pyruvate. Malate oxidation contributed significantly to respiration supported by pyruvate plus malate, and malate did not act solely as a "sparker" for pyruvate oxidation. NAD+-malic enzyme activity was found in sonicated preparations, and comparison of 02 consumption with CO2 released from 1-14C-pyruvate indicated that transported malate was being converted to pyruvate, particularly as the malate to pyruvate ratio increased. The results suggest that pyruvate transport becomes limiting under conditions of high energy demand, but that rapid malate transport makes up the difference, supplying pyruvate via malic enzyme and replenishing losses of tricarboxylic acid cycle intermediates.
TL;DR: The concentration of phosphoenolpyruvate was higher than normal in the livers of anesthetized rats in conditions like fasting and diabetes in which the rate of gluconeogenesis is known to be higher and the activity of pyruVate kinase lower than normally.
Abstract: The cyclic-AMP-dependent inactivation of pyruvate kinase L has been studied in a crude Sephadex filtrate of isolated hepatocytes. This inactivation requires the presence of Mg-ATP (apparent Km= 0.1 mM) and a half-maximal rate of inactivation was obtained in the presence of 0.15 μM cyclic AMP. It was inhibited by physiological concentrations of phosphoenolpyruvate and by micromolar concentrations of fructose bisphosphate and these inhibitory effects were counteracted by Mg-ATP and by several l-form amino acids such as cysteine, alanine, serine, phenylalanine, which are also ligands of pyruvate kinase. As a rule, it appears that effectors that increase the activity of the enzyme are also those which prevent its cyclic-AMP-dependent inactivation and vice-versa.
Considering the potentially important role of phosphoenolpyruvate concentration in the control of gluconeogenesis, experiments were performed to check if the inhibitory action of this metabolite on the inactivation of pyruvate kinase was of importance in vivo. We found that the concentration of phosphoenolpyruvate was higher than normal in the livers of anesthetized rats in conditions like fasting and diabetes in which the rate of gluconeogenesis is known to be higher and the activity of pyruvate kinase lower than normally. The reverse was true upon sucrose feeding. Inactivation of pyruvate kinase was induced in vivo by the administration of glucagon. This inactivation was less important in the livers with high concentrations of phosphoenolpyruvate and vice-versa. It is proposed that phosphoenolpyruvate exerts an important buffering effect in the variations of the rate of gluconeogenesis.
TL;DR: The results suggest that the cauliflower pyruvate dehydrogenase complex is regulated by a phosphorylation-dephosphorylation mechanism as described by Cleveland.
TL;DR: The most likely hypothesis is that both these enzymes are coded by the same single gene, the slight electrophoretic differences between them being due to post-synthetic tissue-specific changes.
TL;DR: In intact cells, intramitochondrial lactate dehydrogenase competes successfully with the electron transport system for the NADH generated by pyruvate metabolism, and conclusions suggested by the accumulation of certain metabolites are discussed in relation to control of citric acid cycle activity.
TL;DR: The results indicate that the intramitochondrial lactate dehydrogenase X, which is unique to spermatozoa, allows the NADH resulting from pyruvate oxidation to reduce other pyruVate molecules to lactate, and pyruviate rapidly repletes the acetylcarnitine pool under a variety of conditions.
TL;DR: The inhibition of PDH both before and after activation suggests a direct arsenic effect on pyruvate utilization which does not involve a lipoic acid moiety, and evidence is presented which indicates an arsenic effects on the regulating kinase and/or phosphatase.
Abstract: Our studies illuminate a particular site of altered pyruvate utilization by liver mitochondria isolated from arsenic-fed rats. Initially, pyruvate dehydrogenase (PDH) levels were measured before and after in vitro activation. The liver homogenates were prepared from male rats given access to deionized drinking water solutions containing 0, 20, 40, and 85 ppm arsenic as sodium arsenate (As+5) for 3 and 6 weeks. After 3 weeks, the effects of arsenic at the highest dose level were pronounced on the basal activity (before activation), with inhibition up to 48% of the control values. The total PDH (after activation) was inhibited by 14, 15, and 28% of the control values at 20, 40, and 85 ppm As+5, respectively. A similar pattern of inhibition of PDH was observed at 6 weeks, although the inhibition was lower at the highest dose. This effect is probably a reflection of mitochondrial regeneration at this time and dose. The inhibition of PDH both before and after activation suggests a direct arsenic effect on pyruvate utilization which does not involve a lipoic acid moiety. Evidence is also presented which indicates an arsenic effect on the regulating kinase and/or phosphatase. The metabolic effects of impaired mitochondrial utilization by pyruvate are also discussed.
TL;DR: The conformations adopted by pyruvate kinase in the presence of allosteric inhibitors make it a better substrate for the protein kinase, compared with mixed histone or a synthetic heptapeptide.
TL;DR: Evidence is provided for the existence in the pyruvate translocator of a single substrate-binding site on the basis of the structural requirements of the binding site and a possible chemical mechanism for the interaction between the substrate and the functional groups of the translocators is proposed.
TL;DR: It is concluded that pyruvate kinase is phosphorylated in the intact liver cell in 32P-labelled slices from rat liver.
TL;DR: The purpose of this work was to study the nature of those two molecular forms of the erythrocyte enzyme in relation to the L-type enzyme from liver.
TL;DR: The pyruvate dehydrogenase complex was purified from Brassica oleracea var.
TL;DR: The activities of 2-oxoglutarate dehydrogenase were measured in hearts and mammary glands of rats, mice, rabbits, guinea pigs, cows, sheep, goats and in the flight muscles of several Hymenoptera to provide a simple method for estimating the maximum flux through the tricarboxylic acid cycle in vivo.
Abstract: 1. The activities of 2-oxoglutarate dehydrogenase (EC 1.2.4.2) were measured in hearts and mammary glands of rats, mice, rabbits, guinea pigs, cows, sheep, goats and in the flight muscles of several Hymenoptera. 2. The activity of 2-oxoglutarate dehydrogenase was similar to the maximum flux through the tricarboxylic acid cycle in vivo. Therefore measuring the activity of this enzyme may provide a simple method for estimating the maximum flux through the cycle for comparative investigations. 3. The activities of pyruvate dehydrogenase (EC 1.2.4.1) in mammalian hearts were similar to those of 2-oxoglutarate dehydrogenase, suggesting that in these tissues the tricarboxylic acid cycle can be supplied (under some conditions) by acetyl-CoA derived from pyruvate alone. 4. In the lactating mammary glands of the rat and mouse, the activities of pyruvate dehydrogenase exceeded those of 2-oxoglutarate dehydrogenase, reflecting a flux of pyruvate to acetyl-CoA for fatty acid synthesis in addition to that of oxidation via the tricarboxylic acid cycle. In ruminant mammary glands the activities of pyruvate dehydrogenase were similar to those of 2-oxoglutarate dehydrogenase, reflecting the absence of a significant flux of pyruvate to fatty acids in these tissues.
TL;DR: Findings indicate that the phosphatase and the kinase do not require an intact tertiary structure in pyruvate dehydrogenase, but apparently recognize components of the local primary sequence around the phosphorylation sites.
TL;DR: The data are consistent with the proposal that changes in the intramitochondrial concentrations of Ca2+ can contribute to the regulation of the activity of pyruvate carboxylase in the liver and under some conditions, change in the mitochondrial Ca*+ concentrations may regulate cellular metabolism through their effects on mitochondrial ATP and pyruVate transport.
TL;DR: It appears that phosphorylation produces a conformational change in pyruvate dehydrogenase that displaces a catalytic group (or groups) at the active center of the enzyme.
TL;DR: It is concluded that the ATP-dependent inactivation-phosphorylation of broccoli and cauliflower mitochondrial PDC is catalyzed by a PDC kinase and is capable of interconversion between an active and an inactive form.
Abstract: The ATP-dependent inactivation of the pyruvate dehydrogenase complex (PDC) was examined using ruptured mitochondria and partially purified pyruvate dehydrogenase complex isolated from broccoli and cauliflower (Brassica oleracea) bud mitochondria. The ATP-dependent inactivation was temperature- and pH-dependent. [32P]ATP experiments show a specific transphosphorylation of the γ-PO4 of ATP to the complex. The phosphate attached to the PDC was labile under mild alkaline but not under mild acidic conditions. The inactivated-phosphorylated PDC was not reactivated by 20 mm MgCl2, dialysis, Sephadex G-25 treatment, apyrase action, or potato acid phosphatase action. However, partially purified bovine heart PDC phosphatase catalyzed the reactivation and dephosphorylation of the isolated plant PDC. The ATP-dependent inactivation-phosphorylation of the PDC was inhibited by pyruvate. It is concluded that the ATP-dependent inactivation-phosphorylation of broccoli and cauliflower mitochondrial PDC is catalyzed by a PDC kinase. It is further concluded that the PDC from broccoli and cauliflower mitochondria is capable of interconversion between an active (dephosphorylated) and an inactive (phosphorylated) form.
TL;DR: It is concluded that ATP/ADP ratio has a pronounced effect on the interconversion of active and inactive pyruvate dehydrogenase, in according with previous work.
TL;DR: It is concluded that, contrary to a previous report, avian liver contains pyruvate kinases type M2 and L as the mammalian liver does.
Abstract: A procedure for the simultaneous purification of both isoenzymes of pyruvate kinase (type M2 and L) from chicken liver has been worked out. Each isoenzyme produces a single band in dodecylsulfate gel electrophoresis. Each has a molecular weight of 190 000 and contains four apparently identical subunits of Mr = 50 000. The isoenzymes differ in their isoelectric points (type L: 6.3; type M2: 8.3) and their kinetic behaviour. Pyruvate kinase type L had an S-shaped phosphoenolpyruvate saturation curve (K 0.5=0.79 mM) which was transformed into an hyperbola in the presence of fructose 1,6-bisphosphate, while type M2 had a phosphoenolpyruvate saturation curve of the Michaelis-Menten type (K0.5=0.2mM). Antibodies against pyruvate kinase type L from chicken liver inactivated type L from rat and partially inactivated type M2 from chicken and rat; but the antibodies against type L did not react with type M1 from chicken breast muscle. It is therefore concluded that, contrary to a previous report (Strandholm, J.J. et al. (1975) Biochemistry 14, 2242-2246), avian liver contains pyruvate kinases type M2 and L as the mammalian liver does.