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.

Changes in the Contents of Metabolites and Enzyme Activities in Rice Plants Responding to Rhizoctonia solani Kuhn Infection: Activation of Glycolysis and Connection to Phenylpropanoid Pathway

Abstract: Rhizoctonia solani Kuhn causes sheath blight disease in rice, and genetic resistance against it is the most desirable characteristic. Current improvement efforts are based on analysis of polygenic quantitative trait loci (QTLs), but interpretation is limited by the lack of information on the changes in metabolic pathways. Our previous studies linked activation of the glycolytic pathway to enhanced generation of lignin in the phenylpropanoid pathway. The current studies investigated the regulation of glycolysis by examining the time course of changes in enzymatic activities and metabolite contents. The results showed that the activities of all glycolytic enzymes as well as fructose-6-phosphate (F-6-P), fructose-1,6-bisphosphate (F-1,6-P(2)), dihydroxyacetone phosphate (DHAP), glyceraldehyde-3-phosphate (GAP), 3-phosphoglycerate (3-PG), phosphoenolpyruvate (PEP) and pyruvate contents increased. These results combined with our previous findings that the expression of phosphoglucomutase (PGM), triosephosphate isomerase (TPI), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), enolase and pyruvate kinase (PK) increased after infection suggested that the additional establishment of glycolysis in the cytosol compartment occurred after infection. Further evidence for this was our recent findings that the increase in expression of the 6-phosphofructokinase (PFK) plastid isozyme Os06g05860 was accompanied by an increase in expression of three cytosolic PFK isozymes, i.e. Os01g09570, Os01g53680 and Os04g39420, as well as pyrophosphate-dependent phosphofrucokinase (PFP) isozymes Os08g25720 (α-subunit) and Os06g13810 (β-subunit) in infected rice plants of the resistant line. The results also showed that the reactions catalysed by PFK/PFP, aldolase, GAPDH + phosphoglycerate kinase (PGK) and PK in leaf sheaths of R. solani-infected rice plants were non-equilibrium reactions in vivo. This study showed that PGM, phosphoglucose isomerase (PGI), TPI and phosphoglycerate mutase (PGmu) + enolase could be regulated through coarse control whereas, PFK/PFP, aldolase, GAPDH + PGK and PK could be regulated through coarse and fine controls simultaneously.

Fructose-2,6-bisphosphate, metabolites and 'coarse' control of pyrophosphate: fructose-6-phosphate phosphotransferase during triose-phosphate cycling in heterotrophic cell-suspension cultures of Chenopodium rubrum.

Abstract: Experiments were carried out to determine whether pyrophosphate: fructose-6-phosphate phosphotransferase (PFP) catalyses the rapid recycling of triose phosphates that is found in the cytosol of heterotrophic cell cultures of Chenopodium rubrum L. (W.-D. Hatzfeld, M. Stitt, 1990, Planta, 180, 198–204). Oxygen uptake, carbohydrate turnover, fructose 2,6-bisphosphate (Fru2,6bisP), glycolytic intermediates, adenine and uridine nucleotides, pyrophosphate and the activity of PFP and glycolytic enzymes were monitored for 48 h after subculturing carbohydrate-depleted cells onto glucose. Immediately after transfer there was an increase in the amount of Fru2,6bisP, and of the hexose phosphate. The triose phosphates, fructose-1,6-bisphosphate and inorganic pyrophosphate increased gradually over the next 24 h. This was accompanied by a tripling in the extractable activity of PFP, but not of phosphofructokinase. The activity of fructose-1,6-bisphosphatase was 20–50fold lower than that of PFP. It is calculated that the activity of PFP is high enough to catalyse the observed rate of cycling between the triose phosphates and the hexose phosphates, based on the measured Vmax capacity of the enzyme, the known kinetic properties, and the measured levels of its reactants and Fru2,6bisP. The changes in the levels of Fru2,6bisP were not correlated with the rate of respiration. Instead, the rate of O2 uptake was inversely related to the phosphoenolpyruvate level, showing that pyruvate kinase or phosphoenolpyruvate carboxylase are regulating the use of glucose for respiration. There was also no relation between Fru2,6bisP, and partitioning to sucrose or starch. It is proposed that the main function of the cycle in these cells is to maintain high levels of inorganic pyrophosphate and triose phosphates, which are necessary for the remobilisation of sucrose and for biosynthesis in the plastid, and that ‘coarse’ and ‘fine’ control of PFP play an important role in regulating this cycle.

Hormonal Control of Gluconeogenesis

Abstract: Gluconeogenesis is the process by which glucose and glycogen are synthesized in the animal body from noncarbohydrate precursors. The liver and the kidney are the two organs which carry out gluconeogenesis and gluconeogenic substrates include lactate, pyruvate, glycerol, and the glucogenic amino acids. Although all the natural amino acids except leucine and lysine are potentially glucogenic by virtue of the fact that they yield pyruvate, oxalacetate, aketoglutarate, succinyl-CoA, or fumarate during their catabolism, studies in the perfused liver indicate that only alanine, serine, proline, threonine, glutamine, asparagine, glutamate, aspartate, and arginine yield significant amounts of carbohydrate (Ross, Hems, and Krebs, 1967).