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Showing papers on "Pyruvate dehydrogenase kinase published in 1975"


Journal ArticleDOI
TL;DR: The possibility that pyruvate transport into mitochondria may be rate limiting and involved in the regulation of gluconegenesis is discussed, and alpha-cyano-4-hydroxycinnamate was shown to be accompanied by the transport of a proton (or by exchange with an OH-ion), which allowed measurements of pyruVate transport at higher temperatures to be made.
Abstract: 1. Studies on the kinetics of pyruvate transport into mitochondria by an 'inhibitor-stop' technique were hampered by the decarboxylation of pyruvate by mitochondria even in the presence of rotenone. Decarboxylation was minimal at 6 degrees C. At this temperature the Km for pyruvate was 0.15 mM and Vmax. was 0.54nmol/min per mg of protein; alpha-cyano-4-hydroxycinnamate was found to be a non-competitive inhibitor, Ki 6.3 muM, and phenyl-pyruvate a competitive inhibitor, Ki 1.8 mM. 2. At 100 muM concentration, alpha-cyano-4-hydroxycinnamate rapidly and almost totally inhibited O2 uptake by rat heart mitochondria oxidizing pyruvate. Inhibition could be detected at concentrations of inhibitor as low as 1 muM although inhibition took time to develop at this concentration. Inhibition could be reversed by diluting out the inhibitor. 3. Various analogues of alpha-cyano-4-hydroxycinnamate were tested on rat liver and heart mitochondria. The important structural features appeared to be the alpha-cyanopropenoate group and the hydrophobic aromatic side chain. Alpha-Cyanocinnamate, alpha-cyano-5-phenyl-2,4-pentadienoate and compound UK 5099 [alpha-cyano-beta-(2-phenylindol-3-yl)acrylate] were all more powerful inhibitors than alpha-cyano-4-hydroxycinnamate showing 50% inhibition of pyruvate-dependent O2 consumption by rat heart mitochondria at concentrations of 200, 200 and 50 nM respectively. 4. The specificity of the carrier for its substrate was studied by both influx and efflux experiments. Oxamate, 2-oxobutyrate, phenylpyruvate, 2-oxo-4-methyl-pentanoate, chloroacetate, dichloroacetate, difluoroacetate, 2-chloropropionate, 3-chloropropionate and 2,2-dichloropropionate all exchanged with pyruvate, whereas acetate, lactate and trichloroacetate did not. 5. Pyruvate entry into the mitochondria was shown to be accompanied by the transport of a proton (or by exchange with an OH-ion). This proton flux was inhibited by alpha-cyano-4-hydroxycinnamate and allowed measurements of pyruvate transport at higher temperatures to be made. The activation energy of mitochondrial pyruvate transport was found to be 113 kJ (27 kcal)/mol and by extrapolation the rate of transport of pyruvate at 37 degrees C to be 42 nmol/min per mg of protein. The possibility that pyruvate transport into mitochondria may be rate limiting and involved in the regulation of gluconegenesis is discussed. 6. The transport of various monocarboxylic acids into mitochondria was studied by monitoring proton influx. The transport of dichloroacetate, difluoroacetate and oxamate appeared to be largely dependent on the pyruvate carrier and could be inhibited by pyruvate-transport inhibitors. However, many other halogenated and 2-oxo acids which could exchange with pyruvate on the carrier entered freely even in the presence of inhibitor.

483 citations


Journal ArticleDOI
TL;DR: The interconversion of the active, nonphosphorylation form of pyruvate dehydrogenase and its inactive, phosphorylated form is modulated by acetyl-CoA/CoA and NADH/NAD molar ratios.

286 citations


Journal ArticleDOI
TL;DR: It is presented that in both adipose tissue and heart muscle, differences in activity of pyruvate dehydrogenase in the intact tissue persist during preparation and subsequent incubation of mitochondria.
Abstract: Dichloroacetate and other halogenated carboxylic acids can activate pyruvate dehydrogenase in rat heart and in rat heart mitochondria by effecting conversion of phosphorylated (inactive) pyruvate dehydrogenase into an active (dephosphorylated) form. These compounds are inhibitors of pig heart pyruvate dehydrogenase kinase. Pig heart pyruvate dehydrogenase phosphate phosphatase requires both Mg2+and Ca2+ for activity. Evidence is given for a dual metal requirement of the phosphatase in rat fat cell mitochondria. It is concluded that Mg2+ and Ca2+ are essential cofactors for the phosphatase but that their physiological significance as regulators remains to be established. Pig heart pyruvate dehydrogenase kinase is inhibited by high concentrations of magnesium and by low concentrations of calcium.

249 citations


Journal ArticleDOI
TL;DR: Under experimental conditions, it was shown that pyruvate utilization can limit acetylcholine synthesis, and this could not be attributed to inhibition of choline acetyltransferase.
Abstract: The relation between pyruvate utilization and acetylcholine synthesis was investigated in minces of adult rat brain. The flux of pyruvate to acetylcholine was less than 1% of that to CO2; nevertheless, a number of agents which inhibited conversion of [1-14C]-pyruvate or [2-14C]pyruvate into 14CO2 were associated with corresponding decreases in the conversion of [2-14C]pyruvate into acetylcholine. The amount of acetylcholine produced by minces of whole rat brain, measured by g.l.c.-mass spectrometry, decreased similarly. Among the inhibitory compounds tested were 3-bromopyruvate, an irreversible inhibitor of pyruvate dehydrogenase; 2-oxobutyrate, a competitive inhibitor of pyruvate dehydrogenase; other 2-oxo acids; and amobarbital and pentobarbital. Linear-regression equations relating CO2 production to acetylcholine synthesis gave correlation coefficients of 0.89-0.93 for the combined observations. The inhibition of acetylcholine synthesis could not be attributed to inhibition of choline acetyltransferase. Incorporation of [2-14C]pyruvate into lipids, proteins and nucleic acids was effected less than that into acetylcholine. Under these experimental conditions, it was shown that pyruvate utilization can limit acetylcholine synthesis.

240 citations


Journal ArticleDOI
TL;DR: Appreciable association was demonstrated under conditions of physiological ionic strength and high protein concentration, and tropomyosin--troponin established as an important and generalized component of these interactions.

220 citations


Journal ArticleDOI
TL;DR: Studies with whole-cell preparations incubated in vitro indicate that alpha-cyano-4-hydroxycinnamate oralpha-cyanocinnamate can be used to specifically inhibit mitochondrial pyruvate transport within cells and thus alter the metabolic emphasis of the preparation.
Abstract: 1. Effects of alpha-cyano-4-hydroxycinnamate and alpha-cyanocinnamate on a number of enzymes involved in pyruvate metabolism have been investigated. Little or no inhibition was observed of any enzyme at concentrations that inhibit completely mitochondrial pyruvate transport. At much higher concentrations (1 mM) some inhibition of pyruvate carboxylase was apparent. 2. Alpha-Cyano-4-hydroxycinnamate (1-100 muM) specifically inhibited pyruvate oxidation by mitochondria isolated from rat heart, brain, kidney and from blowfly flight muscle; oxidation of other substrates in the presence or absence of ADP was not affected. Similar concentrations of the compound also inhibited the carboxylation of pyruvate by rat liver mitochondria and the activation by pyruvate of pyruvate dehydrogenase in fat-cell mitochondria. These findings imply that pyruvate dehydrogenase, pyruvate dehydrogenase kinase and pyruvate carboxylase are exposed to mitochondrial matrix concentrations of pyruvate rather than to cytoplasmic concentrations. 3. Studies with whole-cell preparations incubated in vitro indicate that alpha-cyano-4-hydroxycinnamate or alpha-cyanocinnamate (at concentrations below 200 muM) can be used to specifically inhibit mitochondrial pyruvate transport within cells and thus alter the metabolic emphasis of the preparation. In epididymal fat-pads, fatty acid synthesis from glucose and fructose, but not from acetate, was markedly inhibited. No changes in tissue ATP concentrations were observed. The effects on fatty acid synthesis were reversible. In kidney-cortex slices, gluconeogenesis from pyruvate and lactate but not from succinate was inhibited. In the rat heart perfused with medium containing glucose and insulin, addition of alpha-cyanocinnamate (200 muM) greatly increased the output and tissue concentrations of lactate plus pyruvate but decreased the lactate/pyruvate ratio. 4. The inhibition by cyanocinnamate derivatives of pyruvate transport across the cell membrane of human erythrocytes requires much higher concentrations of the derivatives than the inhibition of transport across the mitochondrial membrane. Alpha-Cyano-4-hydroxycinnamate appears to enter erythrocytes on the cell-membrane pyruvate carrier. Entry is not observed in the presence of albumin, which may explain the small effects when these compounds are injected into whole animals.

191 citations


Journal ArticleDOI
TL;DR: The profile of metabolic intermediates suggests that N6,O2′-dibutyryl adenosine 3′,5′-monophosphate inhibits the conversion of glycogen to pyruvate and lactate by decreasing the effectiveness of phosphofructokinase and pyruVate kinase.

173 citations


Journal ArticleDOI
30 Oct 1975-Nature
TL;DR: The inhibition of pyruvate oxidation by diabetes and by oxidation of fatty acids and ketone bodies is considered to be of crucial importance in the selection of fuels for respiration and in the metabolic changes in heart and other tissues in diabetes and starvation.
Abstract: OXIDATION of pyruvate in perfused rat heart is inhibited by diabetes and by oxidation of fatty acids and ketone bodies1. Enhanced release and oxidation of fatty acids from muscle glycerides may be an important factor in the effects of diabetes2–4. These effects on pyruvate oxidation have generally been attributed to inhibition of pyruvate dehydrogenase, and regulation of this enzyme is considered to be of crucial importance in the selection of fuels for respiration and in the metabolic changes in heart and other tissues in diabetes and starvation.

131 citations


Journal ArticleDOI
TL;DR: It is concluded that the rate of mitochondrial pyruvate metabolisms can be increased by hormones and cyclic nucleotides and that control of mitochondrial pyramid carboxylation is an important regulatory site of hepatic gluconeogenesis.

114 citations


Journal ArticleDOI
TL;DR: The biosynthesis of the four proteins is sensitive to the nature of the carbon sources as well as to the shift from aerobic to anaerobic conditions.

97 citations


Journal ArticleDOI
TL;DR: The data suggest that octanoate addition favors the PDHa kinase reaction leading to inactivation of PDHa, and in addition causes the accumulation of NADH and acetyl-CoA which are recognized competitive inhibitors of pyruvate dehydrogenase.

Journal ArticleDOI
TL;DR: The pyruvate dehydrogenase complex from Axotobacter vinelandii was isolated in a five-step procedure and the partially purified enzyme contains considerable phosphotransacetylase activity.
Abstract: Labelling studies with N-ethylmaleimide show that either in the presence of Mg2+, thiamine pyrophosphate (TPP) and pyruvate or in the presence of NADH the overall activity of the pyruvate dehydrogenase complex from Azotobacter vinelandii is inhibited without much inhibition of the partial reactions. The complex undergoes a conformational change upon incubation with NADH. The inhibition by bromopyruvate is less specific. Specific incorporation of a fluorescent maleimide derivative was observed on the two transacetylase isoenzymes. Binding studies with a similar spin label analogue show that 3 molecules/FAD are incorporated by incubation of pyruvate, Mg2+ and TPP, whereas 2 molecules/FAD are incorporated via incubation with NADH. The spin label spectra support the idea that in the complex the active centres of the component enzymes are connected by rapid rotation of the lipoyl moiety. Three acetyl groups are incorporated in the complex by incubation with [2-14C]pyruvate. Time-dependent incorporation supports the view that the two transacetylase isoenzymes react in non-identical ways with the pyruvate dehydrogenase components of the complex. The results show that the complex contains 2 low-molecular-weight transacetylase molecules and 4 molecules of the high-molecular-weight isoenzyme. Mn2+-binding studies show that the complex binds 10 ions, with different affinities. 2 Mn2+ ions are bound with a 20-fold higher affinity than the remaining 8 Mn2+ ions. The latter 8 ions bind with equal affinities and are thought to reflect binding to the pyruvate dehydrogenase components of the complex. It is concluded that the complex contains 8 pyruvate dehydrogenase molecules, 4 high-molecular-weight transacetylase molecules, 2 low-molecular-weight transacetylase molecules and 1 dimeric (2-FAD-containing) symmetric molecule of lipoamide dehydrogenase. Evidence comes from pyruvate-dependent inactivation and labelling studies that the pyruvate dehydrogenase components contain either an –SH group or an S-S bridge which participates in the hydroxyethyl transfer to the transacetylase components.

Journal ArticleDOI
TL;DR: The activity of pyruvate dehydrogenase in tissue homogenates preincubated with ATP was reduced by 60-75% both in liver of the patient and of the controls and this defect, which was apparent in muscle and liver but not in brain, is attributed to a markedly reduced activity ofpyruvating dehydrogenases phosphatase in the patient.
Abstract: A male child presented on the first day of life with metabolic acidosis with elevated blood lactate (15 mM), pyruvate (0.4 mM), and free fatty acid (1.3 mM) levels and a blood pH of 7.16. The severity of the acidosis was diminished by intravenous administration of glucose in large doses and by bicarbonate. On two occasions, when the acidosis was particularly severe, peritoneal dialysis using an acetate buffer was required. Restriction of the dietary intake of saturated fatty acids or treatment with nicotinic acid also appeared to diminish the severity of acidosis. No improvement was achieved by the administration of thiamine or biotin. Tissues taken at postmortem showed normal activity of gluconeogenic enzymes and pyruvate dehydrogenase. The activity of pyruvate dehydrogenase in tissue homogenates preincubated with ATP was reduced by 60-75% both in liver of the patient and of the controls because of the inactivation of the enzyme by pyruvate dehydrogenase kinase. Addition of Ca++ and Mg++ to the inactivated enzyme caused a prompt return of the activity to normal in controls but not in the patient. This defect, which was apparent in muscle and liver but not in brain, we attribute to a markedly reduced activity of pyruvate dehydrogenase phosphatase in the patient.

Journal ArticleDOI
TL;DR: The rate of pyruvate kinase flux in the intact cell is estimated by a new procedure, involving trapping of 14C from NaH14CO3 in a large pyruVate + lactate pool, and calculation of the specific activity of phosphoenol pyruviate.

Journal ArticleDOI
21 Mar 1975-Science
TL;DR: A complete deficiency in the pyruvate dehydrogenase system activity contributed to the death of a 6-month-old infant with congenital lactic acidosis and showed that the first component is normally present in an apparent excess.
Abstract: A complete deficiency in the pyruvate dehydrogenase system activity contributed to the death of a 6-month-old infant with congenital lactic acidosis. The enzymatic block could be isolated to the first component, pyruvate decarboxylase (E1) of the pyruvate dehydrogenase complex. This enzymatic deficiency allowed a demonstration of an "intercomplex" exchange of the components of the mammalian pyruvate dehydrogenase system and indicated that the first component is normally present in an apparent excess.

Journal ArticleDOI
TL;DR: Ammonium chloride addition to perfused rat liver results in a shift of the steady state of the pyruvate dehydrogenase system towards the active (dephospho) form, interpreted to be mediated in an indirect manner by changes of the mitochondrial concentration of 2-oxoglutarate.
Abstract: 1 Ammonium chloride addition to perfused rat liver results in a shift of the steady state of the pyruvate dehydrogenase system towards the active (dephospho) form This is evidenced by direct measurement of enzyme activity in freeze-stopped liver tissue, by net uptake of pyruvate from the perfusate, and also by an increased release of labeled CO2 from [1-14C]pyruvate Half-maximal concentration of NH4Cl for extra pyruvate uptake is 05–07 mM The effect is readily reversible 2 Extra urea formation upon ammonia addition is matched by an extra O2 uptake as that required theoretically for the two ATP-consuming steps of urea synthesis At 15 mM NH4Cl, there is no significant difference of ATP levels compared to the controls 3 When extra urea formation and the concomitant O2 uptake are suppressed due to limitation at carbamoylphosphate synthesis in carbon-dioxide-free media, the activation of pyruvate dehydrogenase by NH4Cl is still observed 4 When ammonia is generated intracellularly from glutamine, an extra uptake of pyruvate is not observed 5 The NH4Cl-induced activation of pyruvate dehydrogenase is increased in presence of acetoacetate, and decreased in presence of 3-hydroxybutyrate 6 Possible mechanisms are discussed While some of the observations could also be explained by a direct interaction of ammonium ions with the pyruvate dehydrogenase interconversion system, the effect of ammonium ions on pyruvate dehydrogenase is interpreted to be mediated in an indirect manner by changes of the mitochondrial concentration of 2-oxoglutarate As 2-oxoglutarate decreases during reductive amination to glutamate, a pool of high-energy compounds (eg GTP or related substances) dependent upon 2-oxoglutarate oxidation is depleted, resulting in a de-inhibition of pyruvate dehydrogenase by the interconversion system The detailed mechanism of the linkage between 2-oxoglutarate oxidation and pyruvate oxidation remains to be elucidated

Journal ArticleDOI
TL;DR: It is suggested that the input of tricarboxylate-cycle intermediate from proline oxidation is balanced by the formation of pyruvate from malate, and the complete oxidation of the majority of the pyruve, with the possibility of further control at "malic' enzyme.
Abstract: The only exogenous substrates oxidized by mitochondria isolated from the flight muscle of the Japanese beetle (Popillia japonica) are proline, pyruvate and glycerol 3-phosphate. The highest rate of oxygen consumption is obtained with proline. The oxidation of proline leads to the production of more NH3 than alanine, indicating a functioning glutamate dehydrogenase (EC 1.4.1.2). Studies of mitochondrial extracts confirm the presence of a very active glutamate dehydrogenase, and this enzyme is found to be activated by ADP and inhibited by ATP. These extracts also show high alanine aminotransferase activity (EC 2.6.1.2) and a uniquely active "malic' enzyme (EC 1.1.1.39). The "malic' enzyme is activated by succinate and inhibited by ATP and by pyruvate. It is suggested that the input of tricarboxylate-cycle intermediate from proline oxidation is balanced by the formation of pyruvate from malate, and the complete oxidation of the majority of the pyruvate. Studies of the steady-state concentrations of mitochondrial CoASH and CoA thioesters during proline oxidation show a high succinyl (3-carboxypropionyl)-CoA content which falls on activating respiration with ADP. There is a concomitant rise in CoASH. However, the reverse transition, from state-3 to state-4 respiration, causes only very slight changes in acylation. The reasons for this are discussed. Studies of the mitochondrial content of glutamate, 2-oxoglutarate, malate, pyruvate, citrate and isocitrate during the same phases of proline oxidation give results consistent with control at the level of glutamate dehydrogenase and isocitrate dehydrogenase during proline oxidation, with the possibility of further control at "malic' enzyme. During the oxidation of pyruvate all of the tricarboxylate-cycle intermediates and NAD(P)H follow the pattern of changes described in the blowfly (Johnson & Hansford, 1975; Hansford, 1974) and isocitrate dehydrogenase is identified as the primary site of control.?2OAuthor

Journal ArticleDOI
TL;DR: The results show that steric hindrance between the relatively bulky pyruvate dehydrogenase and flavoprotein molecules prevents the transacetylase from binding 24 molecules of each ligand.
Abstract: The binding of pyruvate dehydrogenase and dihydrolipoyl dehydrogenase (flavoprotein) to dihydrolipoyl transacetylase, the core enzyme of the E. coli pyruvate dehydrogenase complex [EC 1.2.4.1:pyruvate:lipoate oxidoreductase (decaryboxylating and acceptor-acetylating)], has been studied using sedimentation equilibrium analysis and radioactive enzymes in conjunction with gel filtration chromatography. The results show that the transacetylase, which consists of 24 apparently identical polypeptide chains organized into a cube-like structure, has the potential to bind 24 pyruvate dehydrogenase dimers in the absence of flavoprotein and 24 flavoprotein dimers in the absence of pyruvate dehydrogenase. The results of reconstitution experiments, utilizing binding and activity measurements, indicate that the transacetylase can accommodate a total of only about 12 pyruvate dehydrogenase dimers and six flavoprotein dimers and that this stoichiometry, which is the same as that of the native pyruvate dehydrogenase complex, produces maximum activity. It appears that steric hindrance between the relatively bulky pyruvate dehydrogenase and flavoprotein molecules prevents the transacetylase from binding 24 molecules of each ligand. A structural model for the native and reconstituted pyruvate dehydrogenase complexes is proposed in which the 12 pyruvate dehydrogenase dimers are distributed symmetrically on the 12 edges of the transacetylase cube and the six flavoprotein dimers are distributed in the six faces of the cube.

Journal ArticleDOI
TL;DR: Alkali-inactivated pig liver pyruvate kinase, type L, and a cyanogen bromide fragment from the same enzyme were shown to be phosphorylated by ( 32 P)ATP and cyclic 3′,5′-AMP-stimulated protein kinase.

Journal ArticleDOI
TL;DR: It is suggested that insulin increases the fraction of pyruvate dehydrogenase present in the tissue in the active dephospho form by increasing the activity of pyRuvatehydrogenase phosphate phosphatase.
Abstract: 1. The mechanism by which insulin activates pyruvate dehydrogenase in rat epididymal adipose tissue was further investigated. 2. When crude extracts, prepared from tissue segments previously exposed to insulin (2m-i.u/ml) for 2min, were supplemented with Mg-2+, Ca-2+, glucose and hexokinase and incubated at 30 degrees C, they displayed an enhanced rate of increase in pyruvate dehydrogenase activity compared with control extracts. 3. When similar extracts were instead supplemented with fluoride, ADP, creatine phosphate and creatine kinase, the rate of decrease in pyruvate dehydrogenase activity observed during incubation at 30 degrees C was unaffected by insulin treatment. 4. It is suggested that insulin increases the fraction of pyruvate dehydrogenase present in the tissue in the active dephospho form by increasing the activity of pyruvate dehydrogenase phosphate phosphatase.

Journal ArticleDOI
TL;DR: In the proximal tubules of the female rat all enzymes studied—except β-hydroxybutyrate dehydrogenase—showed segmental differences, most of them clearly revealing three segments, and sex differences were found concerning all enzymes except uridine diphosphate glucose dehydrogensase and NADP-dependent isocitrate dehydrogenases.
Abstract: The segmentation of the proximal tubules in the kidney of the female rat was studied by means of enzyme histochemical reactions and the results compared with those observed in the male and recently described by Jacobsen and Jorgensen (1973a). Reactions were performed for the following soluble, coenzyme-dependent oxido-reductases: glucose 6-phosphate dehydrogenase, α-glycerophosphate dehydrogenase, 3 α-hydroxysteroid dehydrogenase, NAD-as well as NADP-dependent isocitrate dehydrogenases, NAD-dependent malate dehydrogenase, NADP-dependent, decarboxylating malate dehydrogenase, uridine diphosphate glucose dehydrogenase. Measures were taken to reduce enzyme diffusion and eliminate interference from tissue tetrazolium reductases. Furthermore, reactions were performed for a number of less soluble or insoluble enzymes: glucose 6-phosphatase, mitochondrial α-glycerophosphate dehydrogenase, β-hydroxybutyrate dehydrogenase, succinate dehydrogenase and tetrazolium reductases.


Journal ArticleDOI
TL;DR: The control of pyruvate dehydrogenase activity by inactivation and activation was studied in intact mitochondria isolated from rabbit heart and suggests that pyruVate facilitates its own oxidation and that increases in pyruve dehydrogen enzyme activity by substrate may provide a modulating influence on the utilization of pyrivate via the tricarboxylate cycle.

Journal ArticleDOI
TL;DR: It is demonstrated that, like in isolated mitochondria, a clear correlation between PDH phosphorylation and the mitochondrial ATP/ADP ratio exists in intact liver cells.

Journal ArticleDOI
TL;DR: The data given here suggest that its rate in vivo is probably comparable to the observed rate of glycogen synthesis from lactate, making possible glyconeogenesis in muscle by pyruvate kinase reversal without the need for an enzymatic bypass of the kind employed by liver and kidney.

Journal ArticleDOI
TL;DR: One dominating peptic phosphopeptide was obtained from rat liver pyruvate kinase (type L) phosphorylated by cyclic 3′,5′-AMP-stimulated protein kinase from the same tissue.

Journal ArticleDOI
TL;DR: The results indicate that one part of all enzymes is loosely attached to the inner surface of the membrane as is hemoglobin, and a second part, the "cryptic enzyme activity", is available after resolving by toluene.

Journal ArticleDOI
TL;DR: The heterogeneity of the molecular mechanisms of the deficiency on the one hand, and the abnormalities of electrofocusing patterns on the other hand seem to indicate that erythrocyte PK deficiency is due to the synthesis by muted structural genes of various abnormal PK molecules.
Abstract: Erythrocyte pyruvate kinase (PK) from 5 patients with congenital non-spherocytic hemolytic anemia and erythrocyte PK deficiency have been studied by immunological methods and electrofocusing.

Journal ArticleDOI
TL;DR: Levels of metabolic intermediates in worms incubated aerobically and anaerobically are presented, and ‘cross-over’ plots and calculations of apparent equilibrium constants identify hexokinase, phosphofructokinase and pyruvate kinase as regulatory.

Journal ArticleDOI
TL;DR: The results support the proposition that the mammalian type L pyruvate kinase is a specilized isozyme that is present in mammals but not in birds.
Abstract: Tissues of fetal and adult chickens were examined for pyruvate kinase activity. Two electrophoretically distinguishable and noninterconvertible isozymes were found. One of these, designated as type K (for kidney), is the sole pyruvate kinase in the early fetus and is found in appreciable quantities in all adult tissues except striated muscle. The second isozyme, type M, appears shortly before hatching in striated muscle and brain. These two isozymes correspond in their developmental pattern, tissue distribution, electrophoretic, immunological, and kinetic propertiesto similarly designated mammalian pyruvate kinases. However, no kinetic, immunological, or electrophoretic evidence could be found for a chicken isozyme corresponding to the mammalian type L pyruvate kinase. As the latter isozyme seems to be limited in its distribution mostly to highly differentiated gluconeogenic tissues (notable liver, kidney, and small intestine), our results support the proposition that the mammalian type L pyruvate kinase is a specilized isozyme that is present in mammals but not in birds.