Some Kinetic Properties of Liver Pyruvate Kinase (Type L)

The allosteric effect of fructose bisphosphate on muscle pyruvate kinase studied by infrared spectroscopy

Pyruvate kinase exhibits allosteric properties. The allosteric effect of fructose 1,6-bisphosphate (FBP) on phosphoenolpyruvate (PEP) binding to rabbit muscle pyruvate kinase (PK) in the presence of various ions (Mg(2+), Mn(2+), K(+), Na(+)) was studied by attenuated total reflection infrared spectroscopy in combination with a dialysis accessory. The experiments indicated that FBP binding causes conformational changes of PK that are of the same order of magnitude as those of PEP binding. The conformational change of PEP binding to PK/Mg(2+)/K(+) in the presence of FBP was about twice as large as in its absence, which is tentatively ascribed to a higher occupancy of the closed state. The affinity for PEP increased in the presence of Mg(2+) and K(+). No such effects were observed with the other ion combinations Mn(2+)/K(+) and Mg(2+)/Na(+) or in D(2)O (with Mg(2+)/K(+)), and therefore we did not detect an allosteric effect on PEP binding under these conditions.

Molecular cloning and expression of pyruvate kinase from globefish (Fugu rubripes) skeletal muscle

A cDNA clone encoding pyruvate kinase (PK) was isolated from a skeletal muscle cDNA library of globefish (Fugu rubripes), which is a kind of lower vertebrate. The full-length cDNA of globefish skeletal muscle pyruvate kinase (FM-PK) is approximately 2 kb and encodes a protein comprising 530 amino acids. The FM-PK gene is spanning approximately 4.8 kb and consists of 11 exons. FM-PK mRNA was detected in muscle and heart using Northern blots. The recombinant FM-PK (rFM-PK) was expressed in a baculovirus-insect cell system and purified using ion-exchange chromatography. The purified rFM-PK was shown to exist a 230 kDa homotetramer composed of 57 kDa subunits. Gel filtration showed 230000 as the tetramer of the subunit. The apparent K(m) (or S(0.5)) and the Hill coefficient for phosphoenolpyruvate (PEP) and ADP are 0.14 mM, 1.3 and 0.30 mM 0.98 at pH 7.4, respectively, when the enzyme is saturated with the second substrate. The rFM-PK is strongly activated by fructose-1,6-bisphosphate, the apparent K(m) for PEP changes to 0.059 mM and the Hill coefficient to 1.1. ATP, which is the product of the enzyme reaction, inhibits activity. This is the first report to show the full-length cDNA and amino acid sequence of PK for a species of fish.

Purification and characterization of pyruvate kinase from lamprey (Entosphenus japonicus) muscle

Pyruvate kinase from skeletal muscle of lamprey (Entosphenus japonicus), which is one of the most primitive living vertebrates, has been purified by approxImately 110-fold. The isolation procedure includes chromatography on Phosphocellulose, Phenyl-5PW, and Sephacryl S-300. Sodium dodecyl sulfate gel electrophoresis shows 59000 as the deduced subunit molecular weight and gel filtration shows 232000 as the tetramer of the subunits. The apparent Km for phosphoenolpyruvate and ADP are 0.41 mM and 0.31 mM at pH 7.4, respectively, when the purified enzyme is saturated with the second substrate. When the enzyme is activated in the presence of fructose-1,6-diphosphate, the Km for PEP changes to 0.087 mM, and the Hill coefficient changes from 1.3 to 0.98.

Metal-ion-mediated allosteric triggering of yeast pyruvate kinase. 1. A multidimensional kinetic linked-function analysis

Regulation of the glycolytic pathway is considered to be primarily achieved by the carbon metabolites resulting from glucose metabolism [e.g., fructose 1,6-diphosphate (FDP), phosphoenolpyruvate (PEP), and citrate] and by the ATP charge of the cell. The divalent cations (e.g., Mg2+ and Mn2+) have not been considered as having regulatory roles in glycolysis, although they are involved in almost every enzyme-catalyzed reaction in the pathway. Using a kinetic linked-function analysis of steady-state kinetic data for the interactions of PEP, FDP, and Mn2+ with yeast pyruvate kinase (YPK), we have found that the divalent metal is the principal trigger of the allosteric responses observed with this enzyme. The interaction of Mn2+ to YPK enhances the interaction of FDP by -1.6 kcal/mol and the interaction of PEP by -2.8 kcal/mol. The simultaneous interaction of all three of these ligands to YPK is favored by -4.3 kcal/mol over the sum of their independent binding free energies. Surprisingly, the binding of the allosteric activator FDP does not directly influence the binding of the substrate PEP since a coupling free energy near zero was calculated for these two ligands. Thus, communication between the PEP and FDP sites occurs structurally through the metal by an allosteric relay mechanism. These conclusions are supported by results of a thermodynamic linked-function analysis of direct binding data for the interactions of PEP, FDP, and Mn2+ with YPK [Mesecar, A. D., & Nowak, T. (1997) Biochemistry (following paper in this series)]. Our findings raise important questions as to the possible roles of divalent metals in modulating multiligand interactions with YPK and in the regulation of the glycolytic pathway.

Regulation of arylsulfate sulfotransferase from a human intestinal bacterium by nucleotides and magnesium ion

Arylsulfate sulfotransferase (ASST) from a human intestinal bacterium stoichiometrically catalyzed the transfer of a sulfate group from phenylsulfate esters to phenolic compounds. Pentachlorophenol, one of the selective inhibitors of phenol sulfoconjugation in mammalian tissues, inhibited both phenol and tyramine sulfation by ASST. Nucleotide triphosphates such as ATP, GTP, UTP and CTP, and pyrophosphate inhibited the ASST activity, whereas Mg2+ and Mn2+ activated the enzyme and prevented its inhibition by ATP and pyrophosphate. Equimolar binding of [alpha-] and [gamma-32P]ATP to the enzyme showed that the enzyme protein was not phosphorylated, but bound ATP. These results suggest that nucleotide triphosphates and divalent cations are important modulators in the control of ASST activity.

Some kinetic properties of pyruvate kinase from Trypanosoma brucei

We have studied the kinetics of the allosteric interactions of pyruvate kinase from Trypanosoma brucei. The kinetics for phosphoenolpyruvate depended strongly on the nature of the bivalent metal ions. Pyruvate kinase activated by Mg2+ had the highest catalytic activity, but also the highest S0.5 for phosphoenolpyruvate, while the opposite was true for pyruvate kinase activated by Mn2+. The reaction rates of Mg(2+)-pyruvate kinase and Mn(2+)-pyruvate kinase were clearly allosteric with respect to phosphoenolpyruvate, while the kinetics with Co(2+)-pyruvate kinase were hyperbolic. However, Co(2+)-pyruvate kinase was still sensitive to heterotropic activation. Trypanosomal pyruvate kinase is unique in that the best activator was fructose 2,6-bisphosphate. Ribulose 1,5-bisphosphate and 5-phosphorylribose 1-pyrophosphate were also strong heterotropic activators, which were much more effective than fructose 1,6-bisphosphate and glucose 1,6-bisphosphate. In the presence of the heterotropic activators, the sigmoidal kinetics with respect to phosphoenolpyruvate and the bivalent metal ions were modified as were the concentrations of phosphoenolpyruvate and the bivalent metal ions needed to attain the maximal activity. Maximal activities were not significantly changed with Mg2+ and Mn2+ as the activating metal ions. Moreover, with Co2+ and fructose 2,6-bisphosphate or ribulose 1,5-bisphosphate or 5-phosphorylribose 1-pyrophosphate, the maximal activity was significantly reduced. Ribulose 1,5-bisphosphate and 5-phosphorylribose 1-pyrophosphate resembled fructose 2,6-bisphosphate rather than fructose 1,6-bisphosphate and glucose 1,6-bisphosphate in their action in that the K0.5 values for the former 3 compounds increased when Mg2+ was replaced by Co2+, while the K0.5 for fructose 1,6-bisphosphate and glucose 1,6-bisphosphate increased.(ABSTRACT TRUNCATED AT 250 WORDS)

A kinetic study of the pH effect on the allosteric properties of pyruvate kinase from Phycomyces blakesleeanus

This paper reports the pH-dependence of the allosteric kinetics of Phycomyces blakeseeanus pyruvate kinase with phosphoenol pyruvate and Mg2+ ions in the presence and in the absence of fructose 1,6-bisphosphate (allosteric activator) and L-alanine (allosteric inhibitor). Hydrogen ions increase the affinity of the inhibitory binding sites for phosphoenol pyruvate and Mg2+ ions. Assuming partial conformational states of high and low affinity for inhibitory binding sites, the data presented are in good agreement with the predictions postulated by the two-state concerted-symmetry model of Monod, Wyman, and Changeux. Fructose-1,6-bisphosphate and L-alanine show opposite effects on the interactions of phosphoenol pyruvate and Mg2+ ions with their respective catalytic and inhibitory binding sites. At pH 6.0, the regulation of the Phycomyces pyruvate kinase activity by the concentrations of phosphoenol pyruvate and Mg2+ ions is controlled mainly by L-alanine.

Physical and catalytic properties of pyruvate kinase from pig dental pulp

By ammonium-sulphate fractionation, phosphocellulose column chromatography, and isoelectric focusing, pyruvate kinase (EC 2.7.1.40) was purified from pig dental pulps to yield a homogeneous preparation with a single protein band of approx. 63,000 daltons upon SDS-polyacrylamide gel electrophoresis. As the molecular weight of the enzyme was estimated to be 250,000 by Sephadex G-200 gel filtration, a tetrameric structure is indicated. The isoelectric point of the purified enzyme was 8.0; the optimal pH, pH 7.2. At this pH, there was no substrate inhibition of the enzyme by either phosphoenolpyruvate (PEP) or ADP, and the relationship between reaction velocity and each substrate concentration was well-explained by the Michaelis-Menten equation. The Km values were 53 and 286 microM for PEP and ADP, respectively. The enzyme had different catalytic properties at pH 8.0: with 0.4 mM ADP, the kinetic behaviour gave a sigmoidal curve with respect to PEP and fructose-1,6-diphosphate acted as an allosteric activator. With 2.0 mM ADP, a hyperbolic curve resulted with PEP.

The effect of pH on the interaction of substrates and effector to yeast and rabbit muscle pyruvate kinase

The interaction of fructose 1,6-bisphosphate, phosphoenolpyruvate and ADP with pyruvate kinase (ATP: pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from yeast and rabbit muscle has been studied as a function of pH utilizing the quenching of protein fluorescence at 330 nm by these ligands. Both the muscle and the yeast pyruvate kinase interact with either ADP or phosphoenolpyruvate with similar affinity, indicating that the substrate-binding sites for these two isozymes are similar. The major difference between the yeast and muscle isozymes is their affinity with fructose 1,6-bisphosphate. Fructose 1,6-bisphosphate interacts with the yeast isozyme in orders of magnitude more strongly than with the muscle isozyme. Moreover, the affinity of fructose 1,6-bisphosphate to the yeast isozyme is strongly pH-dependent, while the interaction of fructose 1,6-bisphosphate with the muscle isozyme is independent of pH. The data indicate that yeast pyruvate kinase undergoes a conformational change as the pH is increased from 6.0 to 8.5.

Purification and properties of rat brain pyruvate kinase

Rat brain pyruvate kinase was purified to near homogeneity by a three-step process involving ammonium sulfate precipitation and phosphocellulose and Blue-Sepharose CL-6B column chromatography. The enzyme migrated on polyacrylamide gel along with a commercial sample of rabbit muscle pyruvate kinase. The enzyme showed a hyperbolic relationship with phosphoenolpyruvate and ADP, with apparent Km's of 0.18 and 0.42 X 10(-3) M, respectively. The enzyme was inhibited by ATP, the effect being more pronounced at unsaturating concentrations of phosphoenolpyruvate. L-Phenylalanine was found to be a strong inhibitor of the enzyme, with the Ki for inhibitor being 0.11 mM. The inhibition by phenylalanine was more pronounced at pH 7.4 than at pH 7.0, and appeared to be competitive with phosphoenolpyruvate. L-Alanine and fructose 1,6-bisphosphate prevented the inhibition of the enzyme by phenylalanine. Ca2+ was found to be a strong inhibitor of the enzyme, and the inhibition was more marked at saturating phosphoenolpyruvate concentrations. The kinetic properties of the purified brain pyruvate kinase suggest that the enzyme may be distinct from the muscle or liver enzymes.

Three pyruvate kinase variants with increased affinity for PEP

Three variants of pyruvate kinase are described which have marked reduction of activity associated with severe non-spherocytic haemolytic anaemia. Each variant shows a reduced K0.5 PEP (the value of the intercept of the abscissa on the Hill plot) and reduced Hill coefficient; FDP activation and ATP inhibition are less than normal and utilization of GDP is increased. The variants are slightly less inhibited by 2,3DPG than controls but require more FDP to relieve this inhibition. Cases 1 and 2 have decreased thermostability but case 3 is normal. The mutant enzymes are further distinguished by their affinity for FDP. Their kinetic and physicochemical properties are compared with other known cases with high affinity for PEP and discussed in terms of a R in equilibrium to T model model for allosteric enzymes.

An investigation into the apparent inhibition by arginine phosphate of the activity of Carcinus maenas type-M pyruvate kinase

An enzymic synthesis utilising arginine kinase for preparing arginine phosphate in a high state of purity is described. The dissociation constant of magnesium arginine phosphate, determined by gel filtration, was 30.0 +/- 0.9 mM. That for potassium arginine phosphate was calculated to be 63.0 +/- 4.0 mM measured by the effect of potassium on the apparent magnesium dissociation constant. The effect of KCl on the reaction catalysed by the type-M pyruvate kinase from Carcinus maenas (the common shore crab) pincer and leg muscle was investigated. No effect was seen on the C. maenas pyruvate kinase activity, apart from that due to alteration of the K+ concentration, on adding up to 70 mM potassium arginine phosphate to the reaction medium. The less pure form of arginine phosphate was found to give an apparent noncompetitive inhibition of the enzyme when phosphoenolpyruvate was the varied substrate. This apparent inhibition can be accounted for by the removal of ADP from the assay medium in a side reaction involving arginine kinase and arginine phosphate. These results are discussed in terms of the possible physiological control of the type-M pyruvate kinase from C. maenas.

Acquired pyruvate kinase deficiency. The effect of maleic acid upon human erythrocyte pyruvate kinase

1. Maleic acid is shown to be able to bind the thiol compound 2-mercaptoethanol. This is fully consistent with the data of Morgan and Friedman (1938). 2. Human erythrocyte pyruvate kinase dissolved and quantitated in Tris-maleate shows a loss of positive homotropic interactions, as compared to the same preparation in Tris-HCl. Hill coefficients (n) of n = 1.0-1.2 and n = 1.6-1.8 are obtained in Tris-maleate and Tris-HCl respectively. Half saturation [S] 0.5 and Vmax remain unchanged. Pyruvate kinase in Tris-maleate is slightly more stable to heating at 60 degrees C than in Tris-HCl. Incubation of the enzyme in Tris-maleate for one h with high concentrations of dithiotreitol restores the positive homotropic interactions. 3. It is proposed, that the abnormalities of the pyruvate kinase of some patients with acquired pyruvate kinase deficiency, obtained from a study in Tris-maleate, may partly be induced by the buffer itself.

Steady-state kinetics of smooth muscle myosin

The kinetic properties of purified smooth muscle myosin, free of actin, have been examined. Analysis of the steady-state kinetic data revealed an intermediary plateau region on the substrate saturation curves. In addition, these data, when analyzed by Hill and Lineweaver and Burk plots, indicate both positive and negative cooperativity, suggesting at least four substrate binding sites. The plateau region was abolished when the kinetic measurements were made at pH 5.5 and 9.0. Both positive and negative cooperative effects were absent at pH 9.0 and hyperbolic kinetics was observed. In contrast, at pH 5.5, although the plateau region was abolished, the enzyme exhibited positive cooperativity of substrate binding. When either heated or urea treated enzyme was used for kinetic measurements: (i) the plateau region shifted toward higher substrate concentration range; (ii) the cooperativity of binding sites was lost at low substrate concentrations but was instead seen at higher concentrations; and (iii) the Vmax was doubled. These data have been interpreted as due to ligand-induced conformational changes in the enzyme according to J. Teipel and D. E. Koshland, Jr. (1969).

Biphasic reaction kinetics in an anomalous isozyme of erythrocyte pyruvate kinase

A mutant erythrocyte isozyme of pyruvate kinase (PK) (ATP: pyruvate phosphotransferase, EC 2.7.1.40) has been found in associatin with chronic hemolytic anemia in two siblings who were doubly heterozygous for the isozyme and for quantitative PK deficiency of the usual form. The isozyme was characterized by approximately normal maximum reaction velocities but had markedly decreased affinity for the substrate, phosphoenolpyruvate (PEP), with 5-fold to 10-fold increases in half-saturation constants and decreased interaction between substrate binding sites. Two distinctly separable kinetic patterns for PEP were observed with multiple specimens. Concentrations of fructose 1,6-diphosphate (FDP) required for half-maximal activation were two orders of magnitude greater than controls, and optimal pH was lowered to 6.5. stability at 4 degrees C was markedly decreased, but the lost enzyme could be reactivated by fdp for periods even longer than normal controls.

Interconversion phenomena between two kinetic forms of class a pyruvate kinase from Ehrlich ascites tumor cells

1. The regulatory properties of two interconvertible kinetic forms of class A pyruvate kinase from Ehrlich ascites tumor cells have been studied with a partially purified enzyme preparation free of interfering enzymatic activities. 2. The hyperbolic form shows Michaelis-Menten kinetics for P-pyruvate, with high affinity for this substrate and low affinity for the inhibitory amino acids alanine and phenylalanine. The sigmoidal form displays positive cooperativity respect to P-pyruvate (n=1.4), with lower affinity for this substrate and higher affinity for the inhibitory amino acids. 3. The equilibrium between the hyperbolic and the sigmoidal forms of the enzyme is affected by substraetes and effectors. P-pyruvate, ADP and Fru-P2 shift the equilibrium to the hyperbolic form while ATP, alanine and phenylalanine stabilize the sigmoidal form. 4. Effector metabolites affect the molecular weight of the protein, acting on an equilibrium between dimers and tetramers. P-pyruvate and ADP associate the enzyme to a tetramer while ATP, alanine and phenylalanine favor the occurrence as a dimer. The positive modifier Fru-P2 did not associate the enzyme to the tetramer, even at 1 mM concentration. 5. A tentative molecular model for pyruvate kinase A on the basis of the kinetic and aggregation interconversion is proposed.

Studies on the kinetic effects of adenosine-3':5'-monophosphate-dependent phosphorylation of purified pig-liver pyruvate kinase type L

The effect of cyclic-AMP-dependent phosphorylation on the activity of isolated pig liver pyruvate kinase was studied. It was found that the major kinetic effect of the phosphorylation was to reduce the affinity for the substrate phosphoenolpyruvate, K0.5 for this substrate increasing from 0.3 to 0.9 mM upon phosphorylation. The cooperative effect with phosphoenolpyruvate was enhanced, the Hill constant nH increasing concomitantly from 1.1 to 1.5. V was unaltered. The change in activity occurred in parallel with the phosphate incorporation, except during the initial part of the reaction, when inactivation was correspondingly slower. The affinity for the second substrate ADP was unchanged, with an apparent Km of 0.3 mM at saturating concentration of phosphoenolpyruvate. Likewise, the requirement for potassium was unaffected, whereas the phosphoenzyme required a higher concentration of magnesium ions for maximal activity, compared with the control enzyme. The inhibitory effect of the phosphorylation was counteracted by positive effectors, fructose 1,6-biphosphate in micromolar concentrations completely activated the phosphoenzyme, resulting in an enzyme with properties similar to the fructose 1,6-biphosphate-activated unphosphorylated enzyme, with K0.5 for phosphoenolpyruvate about 0.025 mM and with a Hill constant of 1.1. Hydrogen ions were also effective in activating the phosphoenzyme. Thus, when pH was lowered from 8 to 6.5 the inhibition due to phosphorylation was abolished. The phosphoenzyme was sensitive to further inhibition by negative effectors such as ATP and alanine. 2 mM ATP increased K0.5 for phosphoenolpyruvate to 1.5 mM and nH to 2.3. The corresponding values with alanine were 1.3 mM and 1.9. Phosphorylation is thought to be an additional mechanism of inhibition of the enzyme under gluconeogenetic conditions.

Multienzymic nature of pyruvate kinase during development of Hymenolepis diminuta (Cestoda)

H. diminuta at different stages of development contained as many as five pyruvate kinase isozymes. Four of these were unusually sensitive to allosteric activation by fructose-1,6-P2. One isozyme which occurred only in adults or near-adults was insensitive but had a relatively low Km. All were inhibited by ATP and Ca2+, none by alanine, and the pH optimum was unaffected by fructose-1,6-P2. The five isozymes were present in gravid or reproductively active proglottids. Two of them occurred after eight days growth in the rat intestine, and three after four days. These three were also present in the immature, anterior proglottids of adult parasites. Hexacanth larvae from gravid proglottids, as well as cysticercoids developing from these larvae in Tenebrio molitor, possessed only two isozymes. It was inferred from information on tissue concentrations of ADP, ATP, phosphoenolypyruvate (PEP) and on K0.5S and Km that competition between pyruvate kinase and PEP carboxykinase is probably controlled by fructose-1,6-P2 concentrations. Since H. diminuta is an obligatory fermenter in which gluconeogenesis is minimal, the probable function of its L-type pyruvate kinases is to control the specific composition of lactic, acetic and succinic acid mixtures that are excreted at different stages of development.

Enzymatic pattern of glucose metabolic pathways in pyruvate kinase-deficient erythrocytes

It has been shown that in some cases of congenital non-spherocytic haemolytic anaemia (CNSHA) with pyruvate kinase deficiency, the primary defect may be related to diminished magnesium-stimulated ATPase activity, followed by elevation of the erythrocyte ATP level. ATP as the end product of glycolysis inhibits by negative feedback control the activities of key glycolytic enzymes involved in energy production, i.e. pyruvate kinase (PK) and phosphofructokinase (PFK). Erythrocyte-deficient PK, however, is insensitive to the stimulating effect of fructose 1,6-diphosphate (FDP), which is normally a positive effector of PK. Both competing effectors, i.e. ATP and FDP, seem to show specific interaction. PK, inactive in the presence of high concentrations of ATP, seems to lose its sensitivity to FDP. This effect persists until ATP molecules are present in excess. In vitro incubation of deficient PK with ATPase resulted in increased PK activity as well as in recovery of its sensitivity to the stimulating effect of FDP. The same effects were obtained in vivo by administering magnesium levulinate intravenously to CNSHA patients with PK deficiency. This may indicate that magnesium ions stimulate deficient ATPase activity and lead to diminution of ATP as a negative effector for other regulatory enzymes.

Mathematical analysis of multienzyme systems. I. Modelling of the glycolysis of human erythrocytes

A mathematical model for the glycolysis of human erythrocytes is presented which takes into account ATP-synthesis and -consumption. A set of three differential equations describes the steady states and the time-dependent changes of the metabolite concentrations under blood storage conditions. For a given parameter combination there are in general three stationary points of the system, one of which is unstable. At a low ATP-need the ATP-level is relatively constant for variations in the rate constant of the ATP-consuming processes. Above a critical level of the energy consumption the system breaks down. An important role of the 2.3P2G-bypass of the erythrocytes is its action as an "energy buffer", wasting ATP in case of ATP-overproduction and producing ATP in case of underproduction. A parameter combination consistent with the data on the isolated enzymes was found which gives a good agreement of theoretical predictions with the measured metabolite concentrations. Under blood preservation conditions the difference of the rates of ATP-production and -consumption is the most important factor for a high ATP-level over long periods.