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.

Immunohistological demonstration of the same type of pyruvate kinase isoenzyme (M2-Pk) in tumors of chicken and rat

Abstract: Tumors of chicken and rat contain the M2-type of pyruvate kinase isoenzyme. The amount of this isoenzyme is significantly higher in malignant tumors compared with benign tumors. No alteration of the normal pyruvate kinase isoenzyme pattern was found in hyperplastic tissue.

Regulation of pyruvate kinase type M2 by A-Raf: a possible glycolytic stop or go mechanism.

Abstract: Recently a link between A-Raf cellular energy homeostasis and synthetic pathways has been suggested through the identification of pyruvate kinase type M2 (M2-PK), a key glycolytic enzyme, as interaction partner of A-Raf In this study, we demonstrated that A-Raf is an important regulator of M2-PK function. In primary mouse fibroblasts, which are characterized by glutamine production and serine degradation, A-Raf induced dimerization and inactivation of M2-PK, thereby reducing conversion rates from glucose to lactate. In immortalized NIH3T3 fibroblasts, showing glutamine degradation and serine production, oncogenic A-Raf increased the highly active tetrameric form of M2-PK and favored glycolytic energy production. High serine levels thus may be responsible for the activation of M2-PK in A-Raf transformed NIH3T3 cells.

The Levels of Yeast Gluconeogenic mRNAs Respond to Environmental Factors

Abstract: The FBPl and PCKl genes encode the gluconeogenic enzymes fructose-l,6-bisphosphatase and phosphoenoZpyruv9te carboxykinase, respectively. In the yeast, Saccharomyces cerevisiae, the corresponding mRNAs are present at low levels during growth on glucose, but are present at elevated levels during growth on gluconeogenic carbon sources. We demonstrate that the levels of the FBPl and PCKl mRNAs are acutely sensitive to the addition of glucose to the medium and that the levels of these mRNAs decrease rapidly when glucose is added to the medium at a concentration of only 0.005%. At this concentration, glucose blocks FBPl and PCKl transcription, but has no effect on iso-1 cytochrome c (CYCI) mRNA levels. Glucose also increases the rate of degradation of the PCKl mRNA approximately twofold, but only has a slight effect upon FBPl mRNA turnover. We show that the levels of the FBPl and PCKl mRNAs are also sensitive to other environmental factors. The levels of these mRNAs decrease transiently in response to a decrease of the pH from pH 7.5 to pH 6.5 in the medium, or to a mild temperature shock (from 24°C to 36°C). The latter response appears to be mediated by accelerated mRNA decay. Glycolysis and gluconeogenesis constitute two antagonistic pathways for the metabolism of different carbon sources. Depending on the resources available to the yeast, one pathway or the other is thought to be operational since their simultaneous function would probably cause futile cycles at the level of the antagonistic enzyme pairs phosphofructokinase/fructose-1,6-bisphosphatase and pyruvate kinaselphosphoenoZpyruvate carboxykinase. Tight regulation of these enzymes might therefore be expected, and in fact the enzymes are subject to multiple mechanisms of control, including allosteric regulation, protein inactivation, and changes in enzyme levels [l]. Glucose increases the levels of phosphofructokinase and pyruvate kinase mRNAs due to changes in the transcription rates of the corresponding genes [2]. Also, glucose-grown yeast has barely detectable levels of the mRNAs corresponding to the gluconeogenic genes FBPl and PCKl ,which encode fructose-l,6-bisphosphatase and phosphoenoZpyruvate carboxykinase, respectively [3 -51. Although it is usually assumed that these low levels are due to repression of transcription caused by glucose, glucose could also affect the stability of the mRNAs. To address this question, we measured the half-lives of the gluconeogenic mRNAs in yeast growing on non-fermentable carbon sources

Ruminant hepatic metabolism of volatile fatty acids, lactate and pyruvate.

Abstract: Ruminant liver has a quantitatively unique array of substrates presented to it because of the extensive fermentation of dietary carbohydrate to organic acids in the gastrointestinal tract. The single largest input of dietary energy to the extrasplanchnic tissues is acetic acid derived from fermentation, which is largely unused by hepatic parenchyma. The other volatile fatty acids derived from fermentation, primarily propionate, are cleared extensively, but not completely, by the liver. This results in a marked concentration gradient for these acids across the liver lobule. L-lactate, derived from tissue metabolism, as well as variable amounts from rumen fermentation, is used by the liver at a rate lower than for propionate and below the predicted capacity based on in vitro enzymatic and intact cell capacity data. The net result of this selective utilization by the liver results in peripheral blood containing significant concentrations of L-lactate and acetate, but little of the other organic acids. Propionate carbon metabolized by liver cells is converted to glucose with little true loss of carbon, but the same is not true of lactate carbon. The energetic efficiencies by which propionate and lactate carbon are converted to glucose may be much less than optimal because of extensive cycling through pyruvate kinase, pyruvate carboxylase and phosphoenolpyruvate carboxykinase. Inhibition of this futile cycling may represent one avenue by which energetic costs of maintenance and production can be lowered in ruminants.

Cloning of the pyruvate kinase gene (pyk) of Corynebacterium glutamicum and site-specific inactivation of pyk in a lysine-producing Corynebacterium lactofermentum strain.

Abstract: The pyruvate kinase gene pyk from Corynebacterium glutamicum was cloned by applying a combination of PCR, site-specific mutagenesis, and complementation. A 126-bp DNA fragment central to the C. glutamicum pyk gene was amplified from genomic DNA by PCR with degenerate oligonucleotides as primers. The cloned DNA fragment was used to inactivate the pyk gene in C. glutamicum by marker rescue mutagenesis via homologous recombination. The C. glutamicum pyk mutant obtained was unable to grow on minimal medium containing ribose as the sole carbon source. Complementation of this phenotype by a gene library resulted in the isolation of a 2.8-kb PstI-BamHI genomic DNA fragment harboring the C. glutamicum pyk gene. Multiple copies of plasmid-borne pyk caused a 20-fold increase of pyruvate kinase activity in C. glutamicum cell extracts. By using large internal fragments of the cloned C. glutamicum gene, pyk mutant derivatives of the lysine production strain Corynebacterium lactofermentum 21799 were generated by marker rescue mutagenesis. As determined in shake flask fermentations, lysine production in pyk mutants was 40% lower than that in the pyk+ parent strain, indicating that pyruvate kinase is essential for high-level lysine production. This finding questions an earlier hypothesis postulating that redirection of carbon flow at the phosphoenol pyruvate branch point of glycolysis through elimination of pyruvate kinase activity results in an increase of lysine production in C. glutamicum and its close relatives.