Phosphofructokinase

About: Phosphofructokinase is a(n) research topic. Over the lifetime, 3241 publication(s) have been published within this topic receiving 106624 citation(s).

Transcriptional regulation of genes encoding glycolytic enzymes by hypoxia-inducible factor 1.

Abstract: Hypoxia-inducible factor 1 (HIF-1) activates erythropoietin gene transcription in Hep3B cells subjected to hypoxia. HIF-1 activity is also induced by hypoxia in non-erythropoietin-producing cells, suggesting a more general regulatory role. We now report that RNAs encoding the glycolytic enzymes aldolase A (ALDA), phosphoglycerate kinase 1 (PGK1), and pyruvate kinase M were induced by exposure of Hep3B or HeLa cells to inducers of HIF-1 (1% O2, cobalt chloride, or desferrioxamine), whereas cycloheximide blocked induction of glycolytic RNAs and HIF-1 activity. Oligonucleotides from the ALDA, PGK1, enolase 1, lactate dehydrogenase A, and phosphofructokinase L (PFKL) genes, containing sequences similar to the HIF-1 binding site in the erythropoietin enhancer, specifically bound HIF-1 present in crude nuclear extracts or affinity-purified preparations. Sequences from the ALDA, PFKL, and PGK1 genes containing HIF-1 binding sites mediated hypoxia-inducible transcription in transient expression assays. These results support the role of HIF-1 as a mediator of adaptive responses to hypoxia that underlie cellular and systemic oxygen homeostasis.

Phosphorylation and activation of heart PFK-2 by AMPK has a role in the stimulation of glycolysis during ischaemia.

Abstract: BACKGROUND: The role of protein phosphorylation in the Pasteur effect--the phenomenon whereby anaerobic conditions stimulate glycolysis--has not been addressed. The AMP-activated protein kinase (AMPK) is activated when the oxygen supply is restricted. AMPK acts as an energy-state sensor and inhibits key biosynthetic pathways, thus conserving ATP. Here, we studied whether AMPK is involved in the Pasteur effect in the heart by phosphorylating and activating 6-phosphofructo-2-kinase (PFK-2), the enzyme responsible for the synthesis of fructose 2,6-bisphosphate, a potent stimulator of glycolysis. RESULTS: Heart PFK-2 was phosphorylated on Ser466 and activated by AMPK in vitro. In perfused rat hearts, anaerobic conditions or inhibitors of oxidative phosphorylation (oligomycin and antimycin) induced AMPK activation, which correlated with PFK-2 activation and with an increase in fructose 2,6-bisphosphate concentration. Moreover, in cultured cells transfected with heart PFK-2, oligomycin treatment resulted in a parallel activation of endogenous AMPK and PFK-2. In these cells, the activation of PFK-2 was due to the phosphorylation of Ser466. A dominant-negative construct of AMPK abolished the activation of endogenous and cotransfected AMPK, and prevented both the activation and phosphorylation of transfected PFK-2 by oligomycin. CONCLUSIONS: AMPK phosphorylates and activates heart PFK-2 in vitro and in intact cells. AMPK-mediated PFK-2 activation is likely to be involved in the stimulation of heart glycolysis during ischaemia.

Deregulation of Glucose Transporter 1 and Glycolytic Gene Expression by c-Myc

Abstract: Unlike normal mammalian cells, which use oxygen to generate energy, cancer cells rely on glycolysis for energy and are therefore less dependent on oxygen. We previously observed that the c-Myc oncogenic transcription factor regulates lactate dehydrogenase A and induces lactate overproduction. We, therefore, sought to determine whether c-Myc controls other genes regulating glucose metabolism. In Rat1a fibroblasts and murine livers overexpressing c-Myc, the mRNA levels of the glucose transporter GLUT1, phosphoglucose isomerase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, phosphoglycerate kinase, and enolase were elevated. c-Myc directly transactivates genes encoding GLUT1, phosphofructokinase, and enolase and increases glucose uptake in Rat1 fibroblasts. Nuclear run-on studies confirmed that the GLUT1 transcriptional rate is elevated by c-Myc. Our findings suggest that overexpression of the c-Myc oncoprotein deregulates glycolysis through the activation of several components of the glucose metabolic pathway.

Effect of pH on the Kinetics of Frog Muscle Phosphofructokinase

Abstract: Under appropriate conditions, the activity of phosphofructokinase of skeletal muscle from frog and mouse is extremely sensitive to small changes in pH in the physiological range, a low pH decreasing the affinity of the enzyme for fructose 6-phosphate It is concluded that shifts in intracellular pH are important in the regulation of phosphofructokinase, but that this effect makes interpretation of data from intact muscle quite difficult

Intermediary metabolism of fructose.

Abstract: Most of the metabolic effects of fructose are due to its rapid utilization by the liver and it by-passing the phosphofructokinase regulatory step in glycolysis, leading to far reaching consequences to carbohydrate and lipid metabolism. These consequences include immediate hepatic increases in pyruvate and lactate production, activation of pyruvate dehydrogenase, and a shift in balance from oxidation to esterification of nonesterified fatty acids, resulting in increased secretion of very-low-density-lipoprotein (VLDL). These effects are augmented by long-term absorption of fructose, which causes enzyme adaptations that increase lipogenesis and VLDL secretion, leading to triglyceridemia, decreased glucose tolerance, and hyperinsulinemia. Acute loading of the liver with fructose causes sequestration of inorganic phosphate in fructose-1-phosphate and diminished ATP synthesis. Consequently, the inhibition by ATP of the enzymes of adenine nucleotide degradation is removed and uric acid formation accelerates with consequent hyperuricemia. These effects are of particular significance to potentially hypertriglyceridemic or hyperuricemic individuals.