Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Pyruvate Kinase”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,027 records · Page 57Linked to original sources
PubMed1987

Evidence for two activated forms of pyruvate kinase from Bacillus stearothermophilus in the presence of ribose 5-phosphate.

Allosteric activation of pyruvate kinase from a thermophilic bacterium, Bacillus stearothermophilus, by ribose 5-phosphate (R5P) was kinetically examined. Two activated forms of this enzyme could be distinguished, depending on the R5P concentration. One form (Form I) was observed at about 10(-5) M R5P. It showed a slightly negative cooperativity for phosphoenolpyruvate (PEP). The other form (Form II) was observed at more than 10(-3) M R5P and showed Michaelis-Menten kinetics for PEP. The PEP and ADP concentrations that yield half-maximal velocity were essentially identical for the two forms (about 0.1 and about 0.5 mM, respectively), but Form I had a larger Vmax value than Form II. In the absence of R5P, the enzyme showed a homotropic positive cooperativity for PEP; the concentration required for the half-maximal velocity was about 2 mM and that of ADP was about 1.6 mM. The enzyme was more susceptible to protease digestion in the presence of R5P than in the absence of it. The concentration of R5P required for the enzyme to be susceptible to protease digestion was approximately identical with that required to generate Form I. With more than 10(-3) M R5P, the thermostability of the enzyme was greatly increased. The concentration of R5P required for the enzyme to be thermostable was in good agreement with that required to generate Form II. These results indicate that the two activated forms distinguished kinetically differ in their conformations, too. The saturating level of PEP did not cause such a change in the thermostability or the susceptibility to protease.

Adenosine Diphosphate↗
PubMed1981

Plasma glucagon and insulin concentrations and hepatic phosphoenolpyruvate carboxykinase and pyruvate kinase activities during and upon adaptation of rats to a high protein diet.

Plasma hormones, glucose and free fatty acids, liver glycogen and two key enzymes of glycolysis and gluconeogenesis were examined in adult rats during a 40-day period of high protein feeding. Plasma insulin fell within 1 day but returned to normal after 4 days. Glucagon changed more slowly, reaching a maximum on day 4 and declined to near the control value within 24 days. Consequently, the insulin to glucagon ratio was lower on days 1, 4 and 8 and was nearly normal on day 24. With respect to hepatic enzymes, phosphoenolpyruvate carboxykinase activity rose sharply on the 1st day and remained elevated for 40-day period; the L-isozyme of pyruvate kinase, although unchanged on the 1st day, decreased thereafter and from day 8 on represented 15--20% of control. Circadian variations in these parameters were also measured in rats adapted to the high protein diet. In such animals, the diurnal change in plasma hormones was less marked but tended to be inverted with respect to controls; the insulin/glucagon ratio was highest during daylight on high protein and in late night on the control diet. Over 24 hours, pyruvate kinase activity was related directly and phosphoenolpyruvate carboxykinase inversely to the hormone ratio. We concluded that in rats adapted to high protein, as in controls, the diurnal balance between glycolysis and gluconeogenesis is probably regulated by the same factor, namely the insulin/glucagon ratio.

Animals↗
PubMed2000

Co-existence of hereditary spherocytosis and a new red cell pyruvate kinase variant: PK mallorca.

BACKGROUND AND OBJECTIVE: A partial red blood cell (RBC) pyruvate-kinase (PK-R) deficiency was found in a patient with concomitant hereditary spherocytosis (HS) and chronic hemolytic anemia. Clinical, biological and molecular studies were performed in the patient, his parents and a brother, in order to characterize the specific PK-R gene mutation and the inheritance mechanism of the transmission of both red cell defects in this particular family. DESIGN AND METHODS: Conventional biological studies were used to identify the PK-LR gene mutation responsible for hereditary transmission of PK-R deficiency and HS. The family study was completed with genotypic and RBC membrane protein analyses in the patient and his family. RESULTS: Molecular study of the PK deficiency was performed in all the family members and demonstrated a heterozygous condition for the 1516 G->A (506Val->Ile) mutation at the PK-LR gene in both the patient and his mother. Since this mutation has not been reported previously, it is provisionally named PK "Mallorca". The study of RBC membrane proteins demonstrated the existence of partial band 3 and protein 4.2 deficiencies in the propositus and his father but not in the mother and brother, who were also studied. These results support the dominant mode of inheritance of HS and PK-LR gene in this family. INTERPRETATION AND CONCLUSIONS: HS and PK deficiency are not exceptional in Spain. The co-existence of both RBC defects in the same patient, however, is very rare; only a few cases have been described to date. Our findings suggest that performing an elementary RBC enzyme survey in all patients with HS would help to determine the real frequency of this apparently rare association.

Amino Acid Substitution↗
PubMed2006

[Hereditary enzyme defects of erythrocytes: glucose-6-phosphate dehydrogenase deficiency and pyruvate kinase deficiency].

Possible causes for a normocytic hyperregeneratory anemia are beside an incomplete treatment of iron deficiency, vitamin B12 deficiency or folic acid deficiency notably a hemolysis. After exclusion of other causes of hemolysis like immune hemolytic anemias, microangiopathic hemolytic anemias and hemoglobinopathies, an enzyme deficiency of erythrocytes should be considered. By far the most common form worldwide is the Glucose-6-phosphate deficiency. In the most frequent variants of this disease hemolysis occurs only during stress, imposed for example by infection, "oxidative" drugs or after ingestion of fava beans. The most serious clinical complication of the Glucose-6-phosphate deficiency is the rarely observed neonatal icterus. Some enzyme variants can cause chronic hemolysis which is described as chronic nonsperocytic hemolytic anemia. This form of chronic anemia can also be caused by other enzyme deficiencies, most frequently by the Pyruvate kinase deficiency. All other deficiencies of glycolytic enzymes are even rarer. It should be noted that in some of these very rare forms neurological rather than hematological symptoms predominate the clinical syndrome. If there is suspicion, on the basis of clinical symptoms and/or familial history, diagnosis of an enzyme deficiency can be achieved relatively easy by measurement of the enzyme activity. Accurate diagnosis might be helpful in therapeutic decisions (e.g. splenectomy in certain forms) and it is essential for genetic counseling, since certain deficiencies are transmitted as autosomal recessive disorders (e.g. pyruvate kinase deficiency), while the most common form, the glucose-6-phosphate dehydrogenase deficiency is linked to the X-chromosome.

Anemia, Hemolytic, Congenital↗
PubMed1998

Contribution of malic enzyme, pyruvate kinase, phosphoenolpyruvate carboxylase, and the krebs cycle to respiration and biosynthesis and to intracellular pH regulation during hypoxia in maize root tips observed by nuclear magnetic resonance imaging and gas chromatography-mass spectrometry

In vivo pyruvate synthesis by malic enzyme (ME) and pyruvate kinase and in vivo malate synthesis by phosphoenolpyruvate carboxylase and the Krebs cycle were measured by 13C incorporation from [1-13C]glucose into glucose-6-phosphate, alanine, glutamate, aspartate, and malate. These metabolites were isolated from maize (Zea mays L.) root tips under aerobic and hypoxic conditions. 13C-Nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry were used to discern the positional isotopic distribution within each metabolite. This information was applied to a simple precursor-product model that enabled calculation of specific metabolic fluxes. In respiring root tips, ME was found to contribute only approximately 3% of the pyruvate synthesized, whereas pyruvate kinase contributed the balance. The activity of ME increased greater than 6-fold early in hypoxia, and then declined coincident with depletion of cytosolic malate and aspartate. We found that in respiring root tips, anaplerotic phosphoenolpyruvate carboxylase activity was high relative to ME, and therefore did not limit synthesis of pyruvate by ME. The significance of in vivo pyruvate synthesis by ME is discussed with respect to malate and pyruvate utilization by isolated mitochondria and intracellular pH regulation under hypoxia.

Journal Article↗
PubMed2005

Zinc and 17beta-estradiol induce modifications in Na+/H+ exchanger and pyruvate kinase activity through protein kinase C in isolated mantle/gonad cells of Mytilus galloprovincialis.

We investigated the transduction pathway mediated by Zn and 17beta-estradiol in isolated mantle/gonad cells of the mussel Mytilus galloprovincialis. Both the essential metal Zn, and the estrogen 17beta-estradiol, caused an increase in intracellular pH (pHi) of isolated mantle/gonad cells of the mussel M. galloprovincialis, thus indicating the activation of the Na+/H+ exchanger (NHE). The observed effect was inhibited by EIPA (20 nM), a specific NHE inhibitor, thus verifying NHE activation. Protein kinase C (PKC) also seemed to play an activating role in zinc and 17beta-estradiol effects on NHE and PK activity. In addition, the glycolytic enzyme pyruvate kinase (PK) was increased after zinc, while it was decreased after 17beta-estradiol treatment. It is noteworthy that, both the latter effects were reversed in the presence of EIPA, indicating the involvement of NHE in the signaling mechanism. cAMP seems to participate in the signaling mechanism induced by Zn but not to that induced by 17beta-estradiol. The potential implication of the heavy metal and 17beta-estradiol on the reproductive activity of the marine animals is discussed.

Amiloride↗
PubMed2005

High glucose upregulates pantothenate kinase 4 (PanK4) and thus affects M2-type pyruvate kinase (Pkm2).

A new Rattus norvegicus PanK gene was isolated by mRNA differential display from high concentration glucose-stimulated rat, which encodes a human PanK4-like protein with KOG2201 and KOG4584 domain. Proteins that interact with rat PanK4 were identified by the application of the yeast two-hybrid system. One of the components, Pkm2, was found to be associated with rat PanK4 and its two domains under both in vitro and in vivo conditions. Immunofluorescence staining and confocal scanning experiments showed that PanK4 could transiently co-express with Pkm2 in the cytoplasm of HeLa cell and HEK293T cell. These findings suggest that PanK4 interacts with Pkm2 and thereby may modulate the glucose metabolism through regulating the activity of Pkm2.

Amino Acid Sequence↗
PubMed1977

A kindred with red cell pyruvate kinase deficiency.

A case is described of mild haemolytic anaemia in a female homozygous for pyruvate kinase deficiency, with 20% of normal enzyme activity and with the unexplained associations that she suffers from angina pectoris and that three of her children died in childhood from a muscular dystrophy presumed to be Werdnig-Hoffman disease.

Adolescent↗
PubMed1982

[L and M isoenzymes of hepatic pyruvate kinase and their hormone dependence].

By immunofluorescence and double labelled anti sera L and M pyruvate kinase, there is a double localization of isozymes. It is detected in basal state, in vitro, in isolated hepatocyte, in vivo in experimental or genetic (Zucker rat) hyperinsulinemia or in regenerating liver following partial hepatectomy. It is found in hepatology, in regenerative nodule of cirrhosis and in cancerous cells of liver. This double presence of L and MPK tallies with a specific double hormonodependence: induction of MPK by insulin, and inhibition of LPK by glucagon.

Animals↗
PubMed1982

Enzymatic assays: optimization of systems by using pyruvate kinase and lactate dehydrogenase as auxiliary enzymes.

A method to optimize enzymatic assays by using pyruvate kinase and lactate dehydrogenase enzymes is presented and applied to mitochondrial ATPase as an example. Optimum amounts of auxiliary enzymes, to obtain either a 99% of the initial rate in a given time (t99) or a given lag period (L), are calculated from their apparent Michaelis constants (Kapp) in the medium used and their prices per enzymatic international unit.

Animals↗
PubMed2000

Successful bone marrow transplantation in a child with red blood cell pyruvate kinase deficiency.

We report the first successful use of BMT for the treatment of RBC pyruvate kinase (PK) deficiency in a boy who developed neonatal jaundice and severe transfusion-dependent hemolytic anemia a few months after birth. He received a BMT at the age of 5 from an HLA-identical sister who has normal PK activity after conditioning with busulfan and cyclophosphamide. The post-transplant course was uneventful. At present, 3 years after transplant, he is 8 years old and has a normal hemoglobin level and normal RBC PK activity without evidence of hemolysis. DNA analysis has confirmed full engraftment.

Anemia, Hemolytic↗
PubMed1985

[Pyruvate kinase in mussel foot (Mytilus edulis L.). Purification and general properties].

The specific activity of pyruvate kinase in mussel foot is markedly higher than that from mantle and digestive gland. The foot enzyme shows maximum pH activity in the range between 7.0 and 7.5 and is stable (15 min, 37 degrees C) at pH values between 7.0 and 9.0. The activation energy value is 23 kJ/mol with a Q10 coefficient of 1.4. All of these experiments were carried out using partially purified extracts with (NH4)2SO4 treatment (30-60%) and posterior dialysis with EDTA 1.2 mM. No isoenzymatic forms could be detected using the column chromatography techniques with Sephadex G-150, DEAE Sephadex A-50 and polyacrylamide gel electrophoresis.

Animals↗
PubMed1982

A red cell pyruvate kinase mutant with normal L-type PK in the liver.

The erythrocytic and liver pyruvate kinases (PK) from a patient with congenital nonspherocytic hemolytic anemia have been studied. In red blood cells, the residual activity, 28% of the normal control, presented normal kinetic properties, instability to heat and urea, and slow electrophoretic mobility. The L-type PK from the patient's liver was characterized by normal activity, kinetic properties, stability to heat and urea, and electrophoretic mobility. The fact that erythrocyte mutant PK may, as in previous reports, or may not be associated, as in the present observation, with molecular abnormalities of the liver PK provides support for the hypothesis of a gene rearrangement compatible with two different tissue-specific mRNAs.

Adult↗
PubMed2000

Marked differences between two isoforms of human pyruvate dehydrogenase kinase.

Pyruvate dehydrogenase kinase (PDK) isoforms 2 and 3 were produced via co-expression with the chaperonins GroEL and GroES and purified with high specific activities in affinity tag-free forms. By using human components, we have evaluated how binding to the lipoyl domains of the dihydrolipoyl acetyltransferase (E2) produces the predominant changes in the rates of phosphorylation of the pyruvate dehydrogenase (E1) component by PDK2 and PDK3. E2 assembles as a 60-mer via its C-terminal domain and has mobile connections to an E1-binding domain and then two lipoyl domains, L2 and L1 at the N terminus. PDK3 was activated 17-fold by E2; the majority of this activation was facilitated by the free L2 domain (half-maximal activation at 3.3 microm L2). The direct activation of PDK3 by the L2 domain resulted in a 12.8-fold increase in k(cat) along with about a 2-fold decrease in the K(m) of PDK3 for E1. PDK3 was poorly inhibited by pyruvate or dichloroacetate (DCA). PDK3 activity was stimulated upon reductive acetylation of L1 and L2 when full activation of PDK3 by E2 was avoided (e.g. using free lipoyl domains or ADP-inhibited E2-activated PDK3). In marked contrast, PDK2 was not responsive to free lipoyl domains, but the E2-60-mer enhanced PDK2 activity by 10-fold. E2 activation of PDK2 resulted in a greatly enhanced sensitivity to inhibition by pyruvate or DCA; pyruvate was effective at significantly lower levels than DCA. E2-activated PDK2 activity was stimulated >/=3-fold by reductive acetylation of E2; stimulated PDK2 retained high sensitivity to inhibition by ADP and DCA. Thus, PDK3 is directly activated by the L2 domain, and fully activated PDK3 is relatively insensitive to feed-forward (pyruvate) and feed-back (acetylating) effectors. PDK2 was activated only by assembled E2, and this activated state beget high responsiveness to those effectors.

Acetyl Coenzyme A↗
PubMed1978

The control of pyruvate kinases of Escherichia coli: further studies of the enzyme activated by ribose-5-phosphate.

The pyruvate kinase activated by ribose-5-phosphate from Escherichia coli has been purified to homogeneity, taking advantage of the stabilization of the enzyme by its inhibitor phosphate and by thiol reagents. The native enzyme has a tetrameric quaternary structure which, while prone to dissociation under many conditions, remains intact in the presence of the above reagents. The enzyme was found to reactivate on dilution out of 8 M urea. Interestingly, the recovery of activity is greatly increased by phosphate, an allosteric inhibitor, but markedly reduced by the allosteric activator, ribose-5-phosphate, implying that it is harder for the enzyme to refold to a 'relaxed state.' Proteolysis studies indicate a more open structure in the presence of the activator.

Allosteric Regulation↗
PubMed1982

Cytoimmunochemical study of pyruvate kinase isoenzymes in rat liver.

Using immunofluorescence and double-labelled antisera L and M pyruvate kinase (PK), we show that PK is localized in hepatocyte cytoplasm. The response is modulated by different dietary and hormonal conditions. In physiological conditions, only L PK is noted: slight with normal diet (or 35 micrograms of glucagon) and non-existent with starvation (or 350 micrograms of glucagon). L PK fluorescence is maximal after a carbohydrate-rich diet. In experimental or genetic (Zucker rat) hyperinsulinemia, hepatocytes are both L PK and M PK positive. After partial hepatectomy, this double specificity is found between 48 h and the 7th day. The decrease of PK fluorescence after starvation or glucagon concerns the L PK form of the enzyme. With exo- or endogenous insulin, the increase of PK (as insulinemia assays from Zucker rats or after partial hepatectomy confirm) is essentially due to the presence of M PK in hepatocytes.

Animals↗
PubMed1987

Translation and stability of an Escherichia coli beta-galactosidase mRNA expressed under the control of pyruvate kinase sequences in Saccharomyces cerevisiae.

Plasmids were assembled in which the coding region of the pyruvate kinase (PYK) gene of Saccharomyces cerevisiae was replaced by that of the B-galactosidase (LacZ) gene from Escherichia coli. Analysis of the resultant, chimaeric transcripts from low copy number, centromeric plasmids indicated that this substitution caused a dramatic reduction in the steady-state level of the messenger RNA (mRNA). This fluctuation cannot be wholly accounted for by the 2-fold decrease in mRNA stability observed. This is consistent with the existence of a transcriptional Downstream Activation Site (DAS) within the PYK coding region, analogous to the DAS reported within the yeast phosphoglycerate kinase gene (PGK; Kingsman, S M et al. (1985) Biotech. Gen. Eng. Rev. 3, 377). At these low levels of heterologous gene expression, comparison of the distribution of PYK and PYK/LacZ transcripts across polysome gradients revealed no significant effect mediated by their striking disparity in codon usage. Nevertheless, upon increasing B-galactosidase mRNA levels, via manipulation of plasmid copy number, a distinct decline in ribosome loading was observed for the heterologous PYK/LacZ transcript which was not mirrored by either endogenous PYK transcripts or other yeast mRNAs of high (Ribosomal protein 1) or moderate (Actin) codon bias. However, high levels of the PYK/LacZ mRNA did affect the translation of an endogenous mRNA with poor codon bias (TRP2). The possible basis for this phenomenon is discussed.

Bacterial Proteins↗