Showing papers on "Pyruvate kinase published in 1972"
344 citations
TL;DR: Palmitoyl-CoA inhibition of acetylCoA carboxylase is reversible and competitive with citrate and, therefore, may play an important role in the regulation of fatty acid synthesis in vivo.
183 citations
151 citations
TL;DR: Parenchymal cells prepared by mechanical disruption of mouse liver with 20% polyvinyl alcohol exhibit a similar enzyme profile to those prepared enzymically, and a very substantial increase in the activity ratio of glucokinase to hexokinase over that in total liver homogenate.
Abstract: 1. Parenchymal cells have been prepared from mouse liver by enzymic and mechanical means. 2. The dry weights, protein and DNA contents of these cells have been determined. 3. Mouse liver ‘M-’ and ‘L-type’ pyruvate kinases have been prepared free of contamination with each other; their kinetic properties have been examined and a method has been developed for their assay in total liver homogenates. 4. Recoveries of phosphoglycerate kinase, lactate dehydrogenase and phosphofructokinase in enzymically prepared cells indicate that little, if any, cytoplasmic protein is lost during preparation. 5. Parenchymal cells exhibit a very substantial increase in the activity ratio of glucokinase to hexokinase over that in total liver homogenate; in three out of eight experiments, hexokinase activity was undetectable. 6. ‘L-type’ pyruvate kinase alone occurs in the parenchymal cell. Non-parenchymal cells are characterized by the presence of ‘M-type’ activity only. 7. Parenchymal cells contain both glucose 6-phosphatase and fructose 1,6-diphosphatase. The non-parenchymal fraction appears to contain fructose 1,6-diphosphatase, but is devoid of glucose 6-phosphatase. 8. No aldolase A was detectable in the whole liver. Aldolase B occurs in both parenchymal and non-parenchymal tissue. 9. Parenchymal cells prepared by mechanical disruption of mouse liver with 20% polyvinyl alcohol exhibit a similar enzyme profile to those prepared enzymically. 10. The methodology involved in the preparation of isolated liver cells is discussed. The importance of the measurement of several parameters as criteria for establishing the viability of parenchymal cells is stressed. 11. The metabolic implications of the results in the present study are discussed.
124 citations
112 citations
TL;DR: Analytical data and the results of degradation of glucose, lactate, and glutamate produced from [2-14C]pyruvate or lactate are used to estimate the pathways of carbon flow during active gluconeogenesis in the kidney cortex and it is found that net flux through pyruvates carboxylase and phosphoenolpyruVate carboxykinase may be nearly twice the net rate of glucose formation.
100 citations
TL;DR: The nature of the metabolic changes associated with carbohydrate and fat metabolism that occurred in the blood and liver of lactating dairy cows during starvation for 6 days were determined and were similar to those previously found to occur in cows suffering from spontaneous ketosis.
Abstract: 1. The purpose of this study was to determine the nature of the metabolic changes associated with carbohydrate and fat metabolism that occurred in the blood and liver of lactating dairy cows during starvation for 6 days. 2. During starvation, the blood concentrations of the free fatty acids and ketone bodies increased, whereas that of citrate decreased. After an initial increase, the blood concentration of glucose subsequently declined as starvation progressed. Starvation caused a significant decrease in the plasma concentration of serine and a significant increase in that of leucine. 3. After 6 days of starvation the hepatic concentrations of oxaloacetate, citrate, phosphoenolpyruvate, 2-phosphoglycerate, 3-phosphoglycerate, glucose, glycogen, ATP and NAD(+) had all decreased, as had the hepatic activities of phosphopyruvate carboxylase (EC 4.1.1.32) and pyruvate kinase (EC 2.7.1.40). 4. The above metabolic changes are similar to those previously found to occur in cows suffering from spontaneous ketosis (Baird et al., 1968; Baird & Heitzman, 1971). 5. Milk yield decreased progressively during starvation. 6. There were marked differences in the ability of individual animals to resist the onset of severe starvation ketosis.
98 citations
TL;DR: Following controlled hyperplasia and differentiation after partial hepatectomy complete liver function is restored, whereas in the precancerous liver there is a loss of control of growth and differentiation in some cells resulting in hepatoma formation, which offers a rational explanation of the diverse phenotypes observed in the transplantable Morris liver hepatomas.
94 citations
TL;DR: The results obtained suggest that gluconeogenesis is confined to the parenchymal cells of rat liver, suggesting that Kupffer cells only (probably) contain the M-type pyruvate kinase.
93 citations
TL;DR: Each of the enzymes of gluconeogenesis responded to 48 h fasting with a rise in activity, the extent of which was not apparently related to the previous diet, and the role of the fructose component of sucrose in producing a pattern of adaptation of liver enzymes conducive to lipogenesis and glucose intolerance is discussed.
83 citations
TL;DR: The inhibition of red cell enzymes by copper was completely reversed by the addition of EDTA.
Abstract: Previous studies have shown a marked effect of very high levels of copper on red cell glucose-6-phosphate dehydrogenase and glutathione. When the effect of more nearly physiological levels of copper were studied, red cell hexokinase, phosphofructokinase, phosphoglyceric kinase, pyruvate kinase, and 6-phosphogluconate dehydrogenase were found to be inhibited. Inhibition was observed both when copper was added directly to hemolysates or when hemolysates were prepared from red cells from whole blood which had been incubated with copper and washed. The inhibition of red cell enzymes by copper was completely reversed by the addition of EDTA.
Journal Article•
TL;DR: Tumors originating from each of the tissues studied contained mainly the fetal types of the three enzymes and lacked the adult forms, indicating a tendency for the molecular composition of the several kinds of neoplasms to resemble that of immature rat tissues.
Abstract: Electrophoretic analyses of the isoenzymes of lactate dehydrogenase, aldolase, and pyruvate kinase and chemical analyses of aldolase identified single forms of each that predominated in fetal rat tissues: lactate dehydrogenase 5 (M), aldolase A, and pyruvate kinase K. Other forms of one or more of these enzymes characterized the normal adult liver, kidney, skeletal muscle, and mammary gland tissues. A new finding was the appearance of the cathodic aldolase C in lactating mammary gland. Tumors originating from each of the tissues studied contained mainly the fetal types of the three enzymes and lacked the adult forms. The findings indicate a tendency for the molecular composition of the several kinds of neoplasms to resemble that of immature rat tissues.
TL;DR: The glucagon effect was associated with a marked increase in hepatic cyclic adenosine 3′,5′-monophosphate (cyclic AMP) concentrations and Insulin did not significantly alter hepatic cycling AMP concentrations.
TL;DR: In this article, the effects of varying pH, mono-and divalent cations, temperature, and alternative activators on the rates of proton exchange were reported, indicating that enzyme-bound pyruvate-ATP complex that is generated in the forward reaction can return to substrate form at a significant rate relative to product release.
TL;DR: Evidence is presented that four sulfhydryl residues play a critical role in the activity of pyruvate kinase, and an intramolecular disulfide interchange involving four additional but essential sulfhydyl residues to liberate thionitrobenzoate with the formation of cystine residues is presented.
TL;DR: Possible roles of 2,3-DPG and pyridoxal-5′- P in the regulation of glucose metabolism in red cells are indicated, and the inhibition was competitive; in others, it was noncompetitive.
TL;DR: It is suggested that the above enzymes may not be effectively modulated by the adenylate energy charge, and conditions under which the energy charge model can be best evaluated, limitations of the model, are suggested.
TL;DR: Two forms of hepatic pyruvate kinase, designated type L and type M, were distinguished on the basis of kinetic, chromatographic, electrophoretic and immunological criteria and their properties compared with each other and with the purified enzyme from skeletal muscle.
Abstract: 1. Two forms of hepatic pyruvate kinase, designated type L and type M, were distinguished on the basis of kinetic, chromatographic, electrophoretic and immunological criteria. They were partially purified and their properties compared with each other and with the purified enzyme from skeletal muscle. 2. In contrast with type L, the type M enzyme showed no marked evidence of co-operative interactions with phosphoenolpyruvate and was not stimulated by fructose diphosphate. 3. The activity profiles of type L and type M enzymes were determined in developing rat liver by utilizing differences in the kinetic properties of the two forms. The high activity of type M enzyme in the early foetal rat decreased in late gestation and immediately after birth to reach a low value, which remained essentially constant for the remainder of the developmental period. The activity of type L enzyme, in contrast, was low in the early foetal and neonatal liver but increased markedly at the onset of weaning. 4. Possible roles of the two forms of hepatic pyruvate kinase in the control of glycolysis and gluconeogenesis are discussed.
TL;DR: A purification scheme for human erythrocyte pyruvate kinase was described and the final product was homogeneous as judged by polyacrylamide disc gel electrophoresis and immunodiffusion.
TL;DR: The results indicate that thyroid hormone exerts an important regulatory influence on the activities of hexokinase, phosphofructokinase and pyruvate kinase in the developing cerebral cortex and cerebellum of the rat.
Abstract: — The regulation by thyroid hormone of the activities of hexokinase (ATP: D-hexose 6-phosphotransferase; EC 2.7.1.1), phosphofructokinase (ATP: D-fructose-6- phosphate 1-phosphotransferase; EC 2.7.1.11) and pyruvate kinase (ATP: pyruvate phosphotransferase; EC 2.7.1.40) has been investigated in the soluble fractions of the cerebral cortex and cerebellum of the rat. Ontogenetic studies on these key glycolytic enzymes demonstrated marked increases in the normal cerebral cortex between 1 day and 1 yr of age; less pronounced increases in enzyme activities were noted in the normal cerebellum. Neonatal thyroidectomy, induced by treatment of 1-day-old rats with 100 μCi of 131I, ied to an impairment of body and brain growth and inhibited the developmental increases in hexokinase, phosphofructokinase and pyruvate kinase in both the cerebral cortex and cerebellum. Whereas 50 μCi of 131I had little or no effect on these brain enzymes, 200 μCi of the radioisotope markedly inhibited (35–65 per cent) the developmental increases of the various enzyme activities investigated. When administration of the radioisotope was delayed for 20 days after birth, little or no inhibition of the development of brain glycolytic enzymes was observed. Whereas treatment of normal neonatal animals with L-tri-iodothyronine had no significant effect on the activities of cerebro-cortical and cerebellar glycolytic enzymes, the hormone increased their activities in young cretinous rats. However, when the initiation of tri-iodothyronine treatment was delayed until neonatally thyroidectomized rats had reached adulthood, this hormone failed to produce any appreciable change in enzyme activity. Our results indicate that thyroid hormone exerts an important regulatory influence on the activities of hexokinase, phosphofructokinase and pyruvate kinase in the developing cerebral cortex and cerebellum.
TL;DR: Pyruvate kinase (ATP:pyruvates phosphotransferase, EC 2.7.40) in muscle tissue of the sea mussel Mytilus edulis possesses properties which are similar to allosteric L-type pyruvATE kinase of the rat liver with respect to stimulation by phosphoenolpyruVate and Fru-1,6-P2.
TL;DR: The influence of Glc-1,6-P2 on hepatic and red blood cell pyruvate kinase (ATP: pyruVate phosphotransferase, EC 2.7.40) is quite similar to that of Fru-1-6- P2; the hexose diphosphates can replace each other in stimulating pyruve kinase; after maximal stimulation by one of the compounds, the other is not capable of further stimulation.
TL;DR: The experimental results indicate that the reaction mechanism is of the Ordered Tri Bi type with the substrates binding in the order phosphoenolpyruvate, ADP and Mg(2+).
Abstract: The paper reports a study of the kinetics of the reaction between phosphoenolpyruvate, ADP and Mg2+ catalysed by yeast pyruvate kinase when activated by fructose 1,6-diphosphate and K+. The experimental results indicate that the reaction mechanism is of the Ordered Tri Bi type with the substrates binding in the order phosphoenolpyruvate, ADP and Mg2+. Direct phosphoryl transfer takes place in the quaternary complex, with pyruvate released before MgATP. A dead-end enzyme–pyruvate complex is also indicated. Values have been determined for the Michaelis, dissociation and inhibition constants of the reaction. Several of the rate constants involved have also been evaluated.
TL;DR: In this paper, the authors measured the concentrations of glycolytic intermediates, amino acids and possible regulator substances in locust thoracic muscles perfused under different conditions, and found that butyrate and glucose were present in the perfusion medium, and the aldolase reaction appeared to be inhibited.
Abstract: Concentrations of glycolytic intermediates, amino acids and possible regulator substances were measured in extracts from locust thoracic muscles perfused under different conditions. The conversion of [(14)C]glucose into intermediates and CO(2) by muscle preparations was also followed. When muscles perfused with glucose were made anaerobic changes in metabolite concentrations occurred that could be accounted for by an activation of phosphofructokinase and pyruvate kinase. When butyrate and glucose were present in the perfusion medium the rate of glycolytic flux was lower than with glucose alone, and the aldolase reaction appeared to be inhibited. When butyrate alone was supplied to the muscle the concentrations of most glycolytic intermediates were similar to those found when glucose was supplied. Iodoacetate caused changes in concentrations of intermediates that appeared to result from inhibition of glyceraldehyde 3-phosphate dehydrogenase. Fluoroacetate-poisoned muscles showed a high citrate concentration, but no obvious site of inhibition by citrate was apparent in the glycolytic pathway. Mechanisms for control of glycolysis in locust flight muscle are discussed and related to the known properties of isolated enzymes. It is proposed that trehalase, hexokinase, phosphofructokinase, aldolase, and pyruvate kinase may be control enzymes in this tissue.
TL;DR: Changes in the activity of enzymes involved in glycosis, gluconeogenesis and lipogenesis during the last 7 days of gestation were determined in the placenta and liver of pregnant rats and expressed in relation to the cytoplasmic protein content of these tissues.
TL;DR: The possible role of mitochondria in modifying pyruvate kinase and other ion-sensitive cytoplasmic enzyme activities is discussed.
Abstract: 1. The modification of pyruvate kinase activity in vitro was examined by altering the environmental [Mg2+]/[Ca2+] ratio with EDTA on the one hand and isolated rat liver mitochondria on the other. 2. Controlled additions of Ca2+ and EDTA caused pyruvate kinase activity to be alternately and rapidly switched on and off. 3. By being able to accumulate Ca2+ in preference to Mg2+ rat liver mitochondria were able to alter the [Mg2+]/[Ca2+] ratio in the vicinity of pyruvate kinase and thereby modify the activity of this enzyme. 4. The possible role of mitochondria in modifying pyruvate kinase and other ion-sensitive cytoplasmic enzyme activities is discussed.
TL;DR: Cells from an adult liver when taken into culture resemble fetal liver rather than adult liver, and attempts to induce in these cells the isozymes of ATP-hexose phosphotransferase and pyruvate kinase characteristic of the adult liver have been unsuccessful.
Abstract: Isozyme patterns of the enzymes of ATP-hexose phosphotransferase, aldolase, and pyruvate kinase have been examined in a culture of cells derived from an adult rat liver. Normal adult liver characteristically contains glucokinase, aldolase B, and pyruvate kinase I isozymes. In contrast to this, the isozymes present in the cell line were found to be hexokinase, aldolase A, and pyruvate kinase III. Thus cells from an adult liver when taken into culture resemble fetal liver rather than adult liver. Attempts to induce in these cells the isozymes of ATP-hexose phosphotransferase and pyruvate kinase characteristic of the adult liver have been unsuccessful. The culture conditions were found to affect the nature of the kinetic properties of the pyruvate kinase isozyme in these cells. Cells maintained in the absence of glucose gave a sigmoidal-shaped substrate velocity curve for phosphoenolpyruvate, with aK
m of 0.33mm. However, when the enzyme was extracted from cells grown in the presence of glucose, a hyperbolic-shaped substrate velocity curve was found, with aK
m of 0.05mm. The two forms of this isozyme have been designated A and B, respectively. Form A can be converted to form B by preincubation with fructose diphosphate, whereas the B to A transition is mediated by ethylenediaminetetraacetate, ATP, or citrate. These two forms of the enzyme have distinctive properties in relation to inhibition by ATP, alanine, and phenylalanine, and to activation by fructose diphosphate. Their properties appear to resemble those of adipose tissue pyruvate kinase. The physiological significance of these properties is discussed.