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.

ATP Production in Chlamydomonas reinhardtii Flagella by Glycolytic Enzymes

Abstract: Eukaryotic cilia and flagella are long, thin organelles, and diffusion from the cytoplasm may not be able to support the high ATP concentrations needed for dynein motor activity. We discovered enzyme activities in the Chlamydomonas reinhardtii flagellum that catalyze three steps of the lower half of glycolysis (phosphoglycerate mutase, enolase, and pyruvate kinase). These enzymes can generate one ATP molecule for every substrate molecule consumed. Flagellar fractionation shows that enolase is at least partially associated with the axoneme, whereas phosphoglycerate mutase and pyruvate kinase primarily reside in the detergent-soluble (membrane + matrix) compartments. We further show that axonemal enolase is a subunit of the CPC1 central pair complex and that reduced flagellar enolase levels in the cpc1 mutant correlate with the reduced flagellar ATP concentrations and reduced in vivo beat frequencies reported previously in the cpc1 strain. We conclude that in situ ATP synthesis throughout the flagellar compartment is essential for normal flagellar motility.

Quantitative comparison of the binding of various glycolytic enzymes to F-actin and the interaction of aldolase with G-actin.

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.

Atlantic hagfish cardiac muscle: metabolic basis of tolerance to anoxia

Abstract: Oxygen tensions in the major venous inputs to the systemic and portal-vein hearts of normoxic Atlantic hagfish (12.3 +/- 1.7 and 11.0 +/- 1.6 mmHg, respectively) are low compared with typical vertebrate values. Anoxia and poisoning with cyanide and azide do not significantly affect in situ performance of the systemic heart. Idoacetate poisoning, however, results in a significant decrease in cardiac performance of the systemic heart to 12% of the initial value after 3 h. Activities of mitochondrial enzymes of hagfish ventricle suggest a small potential for aerobic metabolism compared with those in the aerobic ventricle of Atlantic cod. Activities of enzymes of carbohydrate metabolism indicate similar anaerobic capacity in hagfish and cod ventricle. The ratio of pyruvate kinase to cytochrome c oxidase, an index of anaerobic to aerobic capacity, is 5.6 times greater in hagfish than cod ventricle. Metabolite concentrations in freeze-clamped ventricles of normoxic and hypoxic hagfish indicate hypoxia-induced activation of glycogenolysis, enhanced substrate flow across 6-phosphofructokinase, and an apparent secondary constriction of glycolysis at the level of glyceraldehyde-phosphate dehydrogenase. Carbohydrate utilization via the glycolytic pathway appears essential for maintenance of cardiac performance in both normoxic and anoxic hagfish. Under conditions of severe hypoxia, ATP provision is probably met by anaerobic glycolysis.

Glycolytic enzymes and intermediates in carbon catabolite repression mutants of Saccharomyces cerevisiae.

Abstract: Glycolytic parameters were determined in recessive yeast mutants with partial defects in carbon catabolite repression. Specific activities of pyruvate kinase and pyruvate decarboxylase in glucose grown cells of all mutant and wild type stains were 4–5 times higher than in ethanol grown cells. Mutants of gene HEX1 had a reduced hexose phosphorylating activity on allmedia wheras those of gene HEX2 had elevated levels but only in glucose grown cells. Mutants of gene CAT80 were normal in this respect. All other glycolytic enzymes were normal in all mutants. This was also true for glycolytic intermediates. Only hexlmutants showed a reduced fermentation of repressing sugars. The three genes appear to be involved in catabolite repression of several but not of all repressible enzymes. Even though all three types of mutants show a limited overlap in their effects on certain enzymes, they still are distinctly different in their action spectra. Carbon catabolite repression apparently does not depend on the sole accumulation of glycolytic intermediales. The activity of the products of the three genes HEX1, HEX2 and CAT80 are required directly or indirectly for triggering carbon catabolite repression. Even a small segment of carbon catabolite repression is controlled by several genes with regulatory functions indicating that the entire regulatory circuit is highly complex.

The P2X7 receptor is a key modulator of aerobic glycolysis.

Abstract: Ability to adapt to conditions of limited nutrient supply requires a reorganization of the metabolic pathways to balance energy generation and production of biosynthetic intermediates. Several fast-growing cells overexpress the P2X7 receptor (P2X7R) for extracellular ATP. A feature of this receptor is to allow growth in the absence of serum. We show here that transfection of P2X7R allows proliferation of P2X7R-transfected HEK293 (HEK293-P2X7) cells not only in the absence of serum but also in low (4 mM) glucose, and increases lactate output compared with mock-transfected HEK293 (HEK293-mock) cells. In HEK293-P2X7, lactate output is further stimulated upon addition of exogenous ATP or the mitochondrial uncoupler carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP). In the human neuroblastoma cell line ACN, lactate output is also dependent on P2X7R function. P2X7R-expressing cells upregulate (a) the glucose transporter Glut1, (b) the glycolytic enzymes glyceraldehyde 3-phosphate dehydrogenase (G3PDH), (c) phosphofructokinase (PFK), (d) pyruvate kinase M2 (PKM2) and (e) pyruvate dehydrogenase kinase 1 (PDHK1); furthermore, P2X7R expression (a) inhibits pyruvate dehydrogenase (PDH) activity, (b) increases phosphorylated Akt/PKB and hypoxia-inducible factor 1α (HIF-1α) expression and (c) enhances intracellular glycogen stores. In HEK293-P2X7 cells, glucose deprivation increases lactate production, expression of glycolytic enzymes and ph-Akt/PKB level. These data show that the P2X7R has an intrinsic ability to reprogram cell metabolism to meet the needs imposed by adverse environmental conditions.