Showing papers on "Pyruvate kinase published in 1971"
TL;DR: Measurements of the level of metabolic intermediates in acetate-grown cells, before and after the addition of glucose, suggest that isocitrate lyase is controlled in vivo by metabolites other than phosphoenolpyruvate, and that both isocite lyase and isOCitrate dehydrogenase play roles in regulating isocItrate utilization.
356 citations
TL;DR: The glucose-induced increase in glycolytic enzyme activity in Saccharomyces cerevisiae is completely prevented by cycloheximide, an inhibitor of protein synthesis in this yeast.
248 citations
Journal Article•
TL;DR: Several distinct isozymic systems which were observed to have alterations during differentiation from the normal to the neoplastic state have been reviewed, most of these isozymes are key pathway or regulatory enzymes of intermediary metabolism.
Abstract: Summary Several distinct isozymic systems which were observed to have alterations during differentiation from the normal to the neoplastic state have been reviewed Most of these isozymes are key pathway or regulatory enzymes of intermediary metabolism The isozymic systems which were reviewed include DNA polymerase, hexokinase-glucokinase, fructose 1,6-diphosphatase, aldolase, pyruvate kinase, lactate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase, glycerol phosphate dehydrogenase, glutaminase, aspartate aminotransferase, adenylate kinase, carbamylphosphate synthetase, and lactose synthetase The basic isozymic system was outlined, and alterations which occurred in the neoplastic state were discussed in terms of the postulated role for that particular isozymic system in cellular metabolism
136 citations
TL;DR: The stimulatory effect of Fru -1,6-P 2 as well as the inhibitory effect of ATP on the activity of pyruvate kinase were pH dependent and Phosphorylated hexoses and P1 stimulated the activity.
129 citations
TL;DR: Intracellular pH and concentrations of magnesium ion and inorganic pyrophosphate seem to be candidates for controlling factors in some of the photosynthetic processes.
Abstract: Strong regulation of photosynthetic metabolism is maintained by controlled key enzymes within the carbon reduction cycle, on biosynthetic paths leading from it, and within the chloroplast membrane. Of these, the most important are ribulose diphosphate carboxylase, controlling the initial entry of carbon dioxide, and fructose diphosphatase, operating as a portal between carbohydrate metabolism and other biosynthesis, and perhaps playing some role in the selective diffusion of sugar phosphates through the outer chloroplast membrane. Intracellular pH and concentrations of magnesium ion and inorganic pyrophosphate seem to be candidates for controlling factors in some of these processes. These and other control effects have been demonstrated by determinations of metabolite concentrations in green cells and chloroplasts in vivo by tracer techniques. Along biosynthetic paths, pyruvate kinase, which controls the conversion of phosphoenolpyruvic acid to pyruvate, and sucrose phosphate synthetase, which controls sucrose synthesis, play important roles. 61 references, 6 figures.
124 citations
TL;DR: The detection of pyruvate kinase (PyK) activity after electrophoresis on cellulose polyacetate strips is presented, which is sensitive and selective and has the advantage of producing a permanent photographic record.
118 citations
TL;DR: The binding to F-actin of several crystalline rabbit muscle enzymes of glycogenolysis and glycolysis, was investigated in vitro and analysis of the binding characteristics suggests two binding sites in the case of aldolase and pyruvate kinase.
Abstract: The binding to F-actin of several crystalline rabbit muscle enzymes of glycogenolysis and glycolysis, was investigated in vitro. Under the conditions chosen, no binding occurs in the case of glycogen phosphorylase, phosphoglucomutase, glycerate phosphomutase and enolase. Aldolase, pyruvate kinase and triosephosphate dehydrogenase are strongly bound to F-actin, whereas lactate dehydrogenase and phosphoglycerate kinase are bound to a lesser degree. The quantitative differences in the affinity to F-actin are expressed by differences in the determined binding constants. Analytical evaluation of the binding characteristics suggests two binding sites in the case of aldolase and pyruvate kinase. Analytical ultracentrifugation studies and density gradient centrifugation in sucrose revealed a complex formation between aldolase and G-actin monomer. An average s20, w value of 9.2 S was obtained for the complex. At higher aldolase concentration, a gelation of the G-actin was observed which resembles the action of α-actinin.
117 citations
TL;DR: Thallium (I) has been found to serve as the required monovalent cation in the activation of rabbit muscle pyruvate kinase and an inhibition of the reaction occurs which is shown to be most likely due to the formation of the T1 + -ADP complex.
115 citations
TL;DR: This chapter discusses the molecular and kinetic properties, and the physiological significance of pyruvate kinase, which adds strong support to a physiological importance of both the intracellular pH and acetyl-CoA in the control of glycolysis and gluconeogenesis in liver.
Abstract: Publisher Summary This chapter discusses the molecular and kinetic properties, and the physiological significance of pyruvate kinase. From a thermodynamic consideration, these enzymes are especially suited for a control of glycolysis, because they catalyze unidirectional steps driving the metabolic flux into one direction. The combined action of the key enzymes of glycolysis and gluconeogenesis at the control points would allow futile cycles, resulting in the hydrolysis of energy-rich phosphate—an energy-wasting process. Additional regulatory properties of the key enzymes of glycolysis should therefore be expected in tissues that are able to carry out both glycolysis and gluconeogenesis, allowing an opposing control of both metabolic processes. Changes of pH in physiological range would, in addition, allow an opposing control of gluconeogenesis and glycolysis at the level of pyruvate kinase and pyruvate carboxylase reactions. Changes of the pH would not only control pyruvate kinase at suboptimal concentrations of PEP and antagonize the negative control of pyruvate kinase by ATP and alanine, but also control in an opposing way, at suboptimal levels of acetyl-CoA pyruvate carboxylase, the enzyme acting in direction of PEP-synthesis. This relationship adds strong support to a physiological significance of both the intracellular pH and acetyl-CoA in the control of glycolysis and gluconeogenesis in liver.
95 citations
TL;DR: It appears that the properties of thallium-205 are uniquely suitable in this regard for probing macromolecular environment in the presence of paramagnetic ions.
84 citations
TL;DR: It is concluded that this amino acid is an allosteric inhibitor of skeletal muscle pyruvate kinase, independent of pH and it is not reversed by the amino acids.
TL;DR: It is concluded that a lysyl e-amino group in each of the four enzyme subunits may be directly involved in the binding of ADP as well as in the catalytic activity of pyruvate kinase.
TL;DR: The kinetic constants of the fractions from all phenotypes do not differ significantly with respect to ADP and phosphoenolpyruvate and a striking difference was found in enzymic activation by the allosteric effector fructose 1,6-diphosphate.
TL;DR: The results point to the possibility that the activity of this enzyme may regulate the rate of glucose production, and the degree of recycling can be approximated as twice the sum of 14 C in carbons 1 and 3.
TL;DR: The data in this study suggest that the enzyme pyruvate kinase in the oyster occurs in tissue specific multimolecular forms and that the kinetic properties of each isozyme seem to gear in well with the over-all metabolism of the tissue.
TL;DR: Ghosts of human erythrocytes prepared by hypotonic hemolysis were assayed for aldolase, triosephosphate isomerase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate Kinase, pyruvate kinase, lactate dehydrogensase, and glutathione peroxidase and reductase.
Abstract: Ghosts of human erythrocytes prepared by hypotonic hemolysis were assayed for aldolase, triosephosphate isomerase, glyceraldehyde phosphate dehydrogenase, phosphoglycerate kinase, pyruvate kinase, lactate dehydrogenase, and glutathione peroxidase and reductase. Cryptic activity of the enzymes was demonstrated by an increase in activity on dilution with water, which caused fragmentation of the ghosts. Aldolase and glyceraldehyde phosphate dehydrogenase were classed as firmly bound; phosphoglycerate kinase was intermediate; the others were loosely bound. Triton X-100 increased the activities of aldolase, glyceraldehyde phosphate dehydrogenase, and phosphoglycerate kinase. The pH of the medium had little effect upon the firmly bound enzymes but it markedly affected the retention of hemoglobin and the activities of the loosely bound enzymes. The presence of Mg or Ca ions enhanced the retention of hemoglobin and the activity of lactate dehydrogenase and pyruvate kinase, with little effect on aldolase and glyceraldehyde phosphate dehydrogenase. Ghosts diluted in water disintegrated into fragments and tubules or vesicles; Mg or Ca at 1mm afforded protection against this. When ghosts were treated with Triton X-100 and adenosine triphosphate, they contracted to about one-seventh of their volume. The shrunken ghosts had lost a considerable proportion of their cholesterol and protein to the medium.
TL;DR: The properties of pyruvate kinase, together with those of phosphoenolpyruvates carboxylase, aspartokinase, and citrate synthase, seem adapted to provide appropriate partitioning of phosphadenylate between competing pathways in response to metabolic need.
Abstract: Pyruvate kinase (EC 2.7.1.40) from Azotobacter vinelandii responds sharply to the adenylate energy charge, with a decrease in activity at high values of charge, as expected for an enzyme of an adenosine triphosphate-regenerating sequence. Glycolytic intermediates, especially glucose 6-phosphate, fructose 6-phosphate, and fructose-1,6-diphosphate, strongly stimulate the reaction and overcome the inhibition caused by high values of energy charge. Thus, the properties of this enzyme depend on interaction between energy charge and the concentrations of hexose phosphates. The properties of pyruvate kinase, together with those of phosphoenolpyruvate carboxylase, aspartokinase, and citrate synthase, seem adapted to provide appropriate partitioning of phosphoenolpyruvate between competing pathways in response to metabolic need.
TL;DR: In conclusion, inhibition of hexokinase is probably the most significant step in regulation of glycolysis by 2,3-diphosphoglycerate, and its possible significance in mammalian erythrocytes is discussed briefly.
TL;DR: FDP dramatically activates rattail muscle pyruvate kinase (500% activation with 0.1 mM FDP) by reducing the K mPEP, increasing the maximum velocity, and overriding negative ATP modulation of the enzyme.
Abstract: SYNOPSIS. Muscle pyruvate kinase from an abyssal Coryphaenoides species occurs as a single electrophoretic form with an isoelectric point of about pH 6.0. Maximum catalytic rates are dramatically reduced by pressure. For catalysis at 3°C, the volume change of activation, Δ V *, is about 44 cm3/mole (calculated between 14.7 and 8000 psi). The value ot Δ V * decreases at higher temperatures but is pH independent. The activation energy for rattail muscle pyruvate kinase at 14.7 psi is about 13 Kcal/mole and doubles at 12,000 psi. Mg2+ saturation kinetics involve positive site-site interactions. Hill plots yield n values of about 2.4 and Ka values of about 2 mM (at 3°C), and these constants are pressure independent. The Km values for ADP increase slightly with pressure. PEP saturation curves are complex: at high PEP concentrations, the n values are about 2–2.5, while at low PEP levels, values for the Hill constant are about 1.0. The Hill constant lor PEP is not affected by pressure, but the apparent Km increases somewhat with pressure. FDP dramatically activates rattail muscle pyruvate kinase (500% activation with 0.1 mM FDP) by (1) reducing the K mPEP, (2) increasing the maximum velocity, and (3) overriding negative ATP modulation of the enzyme. The latter control feature is strictly dependent upon pressure and is not observed at low pressure. In the presence of FDP, the Km for PEP decreases at high pressures, in this way counteracting the inhibitory effects of pressure. Under low concentrations of substrates, pyruvate kinase activity is probably determined by its kinetic properties and not by energy-volume relationships.
TL;DR: Studies with the partially purified erythrocytic guanylate kinase showed that GMP, dGMP, 8-azaGMP and IMP serve as substrates while UMP, CMP and 6-thioIMP do not.
TL;DR: At least two forms of pyruvate kinase Type M can be distinguished in rat tissues on the basis of kinetic properties, and the inhibition by phenylalanine and alanine of the liver pyruviate kinases Type M is of the mixed type with respect to phosphoenol pyruVate and is only slightly dependent on pH.
TL;DR: The relationship between changes of the cytosolic pyridine nucleotide oxidation-reduction state and the overall control of gluconeogenesis is clarified.
Abstract: The notion is presented that recycling of carbon between the steps pyruvate to P-enolpyruvate, and fructose diphosphate to fructose-6-P, is involved in the overall control of hepatic gluconeogenesis in both normal and pathological states. This results in a higher than theoretical energy cost for gluconeogenesis, which may be revealed by low apparent P:O ratios when calculated on the basis of the theoretical increment of 6 moles of ATP used per mole of glucose formed, compared with the observed increment of respiration when the rate of gluconeogenesis is altered. The concept is developed that the rate of gluconeogenesis is controlled either directly by changes in the concentration of factors modifying pyruvate carboxylase or indirectly by alterations of the activity of pyruvate kinase. If the activity of the latter enzyme is increased, flux through the loop Pyr → OAA → PEP → Pyr will be increased and net gluconeogenesis decreased. Since the inhibitory effects of alanine and ATP on pyruvate kinase can be overcome by low concentrations of fructose diphosphate, interactions in the segment of the gluconeogenic pathway from P-enolpyruvate to glucose, although not able to affect gluconeogenesis flux directly, can control it indirectly by alterations of the fructose diphosphate concentration. Interactions discussed are variations of the citrate concentration, which will affect the activity of phosphofructokinase, and altered metabolic states caused by changes of the state of reduction of the cytosolic pyridine nucleotides. By taking into account the possibility that high rates of carbon recycling between pyruvate and P-enol-pyruvate occur relative to the net rate of gluconeogenesis, the relationship between changes of the cytosolic pyridine nucleotide oxidation-reduction state and the overall control of gluconeogenesis is clarified.
TL;DR: A model is proposed for the interactions of Blue Dextran with phosphofructokinase, postulating binding of the chromophore to the ATP binding sites of the enzyme.
Abstract: Yeast phosphofructokinase binds to Blue Dextran 2000® with remarkable high affinity. Whereas phosphofructokinase from muscle and erythrocytes also have high affinity to Blue Dextran, aldolase, hexokinase, pyruvate kinase from muscle and glyceraldehyde-3-phosphate dehydrogenase show no affinity to this chromophore.
The chromophoric component of Blue Dextran seems to be responsible for these interactions, because chromophore-free dextran 2000 does not show any affinity to phosphofructokinases.
Blue Dextran immobilized by fixation in cross-linked polyacrylamide gel can be used as a valuable tool for affinity chromatography of phosphofructokinase. The conditions of binding, namely pH dependence, effects of ionic strength and of enzyme effectors have been studied using gel-fixed phosphofructokinase. ATP (2–3 mM) but not ITP (up to 5 mM) specifically splits the enzyme chromophore complex.
With non-inhibitory concentrations of ATP Blue Dextran inhibits the enzyme very strongly showing competition with respect to ATP. No correlation between inhibition by Blue Dextran and fructose-6-phosphate concentration could be detected.
A model is proposed for the interactions of Blue Dextran with phosphofructokinase, postulating binding of the chromophore to the ATP binding sites of the enzyme.
TL;DR: Rabbit muscle phosphoglycerate kinase (EC 2.7.2.3) has been phosphorylated with γ-32P-ATP and then isolated by gel filtration, and the pH stability profile of the phosphoenzyme is U-shaped, which accord with a covalent binding of the phosphate group to a carboxyl of the enzyme.
TL;DR: It is argued that glycolysis and the pentose phosphate pathway make substantial contributions to carbohydrate oxidation in both stele and cortex and it is suggested that the formation and maturation of the stele is accompanied by an increase in the capacity of the pentoses phosphate pathway relative to that of glycoleysis.
TL;DR: Data on the metabolites produced from 2-deoxyglucose have been interpreted to suggest that glucose-6-P is the inducer of the following enzymes: aldolase, triose-p isomerase, P-glycerate mutase, enolases, and pyruvate kinase.
TL;DR: Human erythrocyte pyruvate kinase (EC 2.7.1.40) was isolated in forms with K0.5 s values for phosphoenolpyruVate which range from 3 x 10-5 m to greater than 10-3 m, and another apparently distinct form of enzyme was found in lysates of fresh blood cells.