Pyruvate kinase

About: Pyruvate kinase is a research topic. Over the lifetime, 5683 publications have been published within this topic receiving 180020 citations. The topic is also known as: ATP:pyruvate 2-O-phosphotransferase & phosphoenolpyruvate kinase.

MiR-133b inhibits growth of human gastric cancer cells by silencing pyruvate kinase muscle-splicer polypyrimidine tract-binding protein 1.

Abstract: The metabolism in tumor cells shifts from oxidative phosphorylation to glycolysis even in an aerobic environment. This phenomenon is known as the Warburg effect. This effect is regulated mainly by polypyrimidine tract-binding protein 1 (PTBP1), which is a splicer of the mRNA for the rate-limiting enzymes of glycolysis, pyruvate kinase muscle 1 and 2 (PKM1 and PKM2). In the present study, we demonstrated that miR-133b reduced PTBP1 expression at translational level and that the expression levels of miR-133b were significantly downregulated in gastric cancer clinical samples and human cell lines, whereas the protein expression level of PTBP1 was upregulated in 80% of the 20 clinical samples of gastric cancer examined. Ectopic expression of miR-133b and knockdown of PTBP1 in gastric cancer cells inhibited cell proliferation through the induction of autophagy by the switching of PKM isoform expression from PKM2-dominant to PKM1-dominant. The growth inhibition was partially canceled by an autophagy inhibitor 3-MA or a reactive oxygen species scavenger N-acetylcysteine. These findings indicated that miR-133b acted as a tumor-suppressor through negative regulation of the Warburg effect in gastric cancer cells.

Regulation of lactose fermentation in group N streptococci.

Abstract: Group N streptococci, which have the lactose phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) and phospho-β-d-galactosidase (β-Pgal), grew rapidly on lactose and converted more than 90% of the sugar to l-lactate. In contrast, Streptococcus lactis 7962, which does not have a β-Pgal, grew slowly on lactose and converted only 15% of the sugar to l-lactate. With glucose and galactose, this strain had growth rates and fermentation patterns similar to those of other S. lactis strains, suggesting that the rapid and homolactic fermentation of lactose that is characteristic of group N streptococci is dependent upon a functional PEP-dependent PTS and the presence of β-Pgal. Seventeen strains of group N streptococci were examined for the activator specificities of pyruvate kinase and lactate dehydrogenase. The properties of each enzyme from all the strains, including S. lactis 7962, were similar. Pyruvate kinase had a broad activator specificity, whereas activation of lactate dehydrogenase was specific for ketohexose diphosphate. All intermediates of lactose metabolism from the hexose phosphates to the triose phosphates activated pyruvate kinase. No activation was obtained with adenosine 5′-monophosphate. K+ and Mg2+ were required for pyruvate kinase activity but could be replaced by NH4+ and Mn2+, respectively. Lactate dehydrogenase was activated equally by fructose-1,6-diphosphate and tagatose-1,6-diphosphate, the activation characteristics being pH dependent. The roles of pyruvate kinase and lactate dehydrogenase in the regulation of lactose fermentation by group N streptococci are discussed.

Studies on Respiration and Glycolysis in Transplanted Hepatic Tumors of the Rat

Abstract: Summary In a continuation of studies on glycolytic and respiratory interrelationships in a series of rat hepatomas ranging widely in growth rate and degree of differentiation, whole, fortified homogenates of these tissues were incubated at 28°C in the presence of fructose-1,6-diphosphate (FDP), 2-deoxyglucose (2-DG), and exogenous hexokinase; respiration, lactate formation, and uptake of 2-DG were measured. Preliminary studies with this model system established that uptake of 2-DG was a valid measure of ATP formation. On the assumption that each mole of lactate formed from FDP leads to production of 2 moles of ATP via phosphoglycerate kinase and pyruvate kinase, glycolytic phosphorylation was estimated as twice that of lactate, and respiratory phosphorylation was calculated as the difference between total ATP and glycolytic ATP formation. Without exogenous substrate, respiration was high in homogenates of well-differentiated tumors, and low in those of poorly differentiated tumors. In both tumor types respiration was coupled with ATP formation, yielding P/O ratios of 1 to 2. Addition of FDP to liver homogenates resulted in moderate lactate and glycolytic ATP formation, the latter being formed largely at the expense of respiratory phosphorylation. In homogenates of well-differentiated tumors, lactate formation and glycolytic phosphorylation were low, and neither respiration nor respiratory phosphorylation was decreased. In contrast, homogenates of the poorly differentiated hepatomas exhibited high lactate formation, and though respiration was increased somewhat by FDP addition, essentially all of the ATP was formed via glycolysis. It thus appears that, in this system, transphosphorylating enzymes of glycolysis are a major site of glycolytic control, presumably through competition with the respiratory ADP acceptors for the available ADP. Further evidence for such competition was obtained by intermixing the supernatant and particulate fractions. Replacement of particles from a low-respiring, poorly differentiated tumor by particles from a high-respiring, well-differentiated tumor resulted in a pronounced Pasteur effect; respiration was increased, together with respiratory ATP production, while glycolysis was markedly decreased. However, when particles of a high-respiring tumor were replaced with particles of a low-respiring tumor, respiration and respiratory phosphorylation were decreased and glycolysis was markedly increased. These findings provide evidence for the suggestion offered many years ago by Johnson and by Lynen that the Pasteur effect may reflect competition for ADP and inorganic phosphate (P 1 ) at the transphosphorylating sites of glycolysis and respiration. They also suggest that the high aerobic glycolysis which is, in general, characteristic of highly dedifferentiated tumors may be, in part, a resultant of their low respiratory activity and high levels of glycolytic transphosphorylating enzymes.

Pyruvate kinase M2 is requisite for Th1 and Th17 differentiation.

Abstract: Th1 and Th17 are important in the pathogenesis of autoimmune diseases and they depend on glycolysis as a source of energy. T cell antigen receptor signaling phosphorylates a serine/threonine kinase, calcium/calmodulin-dependent protein kinase IV (CaMK4), and promotes glycolysis. Based on these findings we hypothesized that CaMK4 promotes glycolysis. Camk4-deficient CD4+ T cells and cells treated with a CaMK4 inhibitor had less glycolysis compared with their counterparts. Pull-down of CaMK4 and mass spectrometry identified pyruvate kinase muscle isozyme (PKM), the final rate-limiting enzyme in glycolysis, as a binding partner. Coimmunoprecipitation and Western blotting showed that CaMK4 interacts directly with PKM2. Camk4-deficient CD4+ T cells displayed decreased pyruvate kinase activity. Silencing or pharmacological inhibition of PKM2 reduced glycolysis and in vitro differentiation to Th1 and Th17 cells, while PKM2 overexpression restored Th17 cell differentiation. Treatment with a PKM2 inhibitor ameliorated experimental autoimmune encephalomyelitis and CD4+ T cells treated with PKM2 inhibitor or Pkm2-shRNA caused limited disease activity in an adoptive cell transfer model of experimental autoimmune encephalomyelitis. Our data demonstrate that CaMK4 binds to PKM2 and promotes its activity, which is requisite for Th1 and Th17 differentiation in vitro and in vivo. PKM2 represents a therapeutic target for T cell-dependent autoimmune diseases.

Enzyme activities of human erythrocyte ghosts: effects of various treatments.

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.