Reversal Of Glycolysis Research Articles

The Discovery of Glyoxysomes: the Work of Harry Beevers

Sucrose Synthesis from Acetate in the Germinating Castor Bean: Kinetics and Pathway (Canvin, D. T., and Beevers, H. (1961) J. Biol Chem. 236, 988–995) Mitochondria and Glyoxysomes from Castor Bean Endosperm. Enzyme Constituents and Catalytic Capacity (Cooper, T. G., and Beevers, H. (1969) J. Biol. Chem. 244, 3507–3513)

Thermodynamics of the Pyruvate Kinase Reaction and the Reversal of Glycolysis in Heart and Skeletal Muscle

The effect of temperature, pH, and free [Mg(2+)] on the apparent equilibrium constant of pyruvate kinase (phosphoenol transphosphorylase) (EC ) was investigated. The apparent equilibrium constant, K', for the biochemical reaction P-enolpyruvate + ADP = ATP + Pyr was defined as K' = [ATP][Pyr]/[ADP][P-enolpyruvate], where each reactant represents the sum of all the ionic and metal complexed species in M. The K' at pH 7.0, 1.0 mm free Mg(2+) and I of 0.25 m was 3.89 x 10(4) (n = 8) at 25 degrees C. The standard apparent enthalpy (DeltaH' degrees ) for the biochemical reaction was -4.31 kJmol(-1) in the direction of ATP formation. The corresponding standard apparent entropy (DeltaS' degrees ) was +73.4 J K(-1) mol(-1). The DeltaH degrees and DeltaS degrees values for the reference reaction, P-enolpyruvate(3-) + ADP(3-) + H(+) = ATP(4-) + Pyr(1-), were -6.43 kJmol(-1) and +180 J K(-1) mol(-1), respectively (5 to 38 degrees C). We examined further the mass action ratio in rat heart and skeletal muscle at rest and found that the pyruvate kinase reaction in vivo was close to equilibrium i.e. within a factor of about 3 to 6 of K' in the direction of ATP at the same pH, free [Mg(2+)], and T. We conclude that the pyruvate kinase reaction may be reversed under some conditions in vivo, a finding that challenges the long held dogma that the reaction is displaced far from equilibrium.

Interactions between carbon and nitrogen metabolism in Fibrobacter succinogenes S85: a 1H and 13C nuclear magnetic resonance and enzymatic study.

The effect of the presence of ammonia on [1-13C]glucose metabolism in the rumen fibrolytic bacterium Fibrobacter succinogenes S85 was studied by 13C and 1H nuclear magnetic resonance (NMR). Ammonia halved the level of glycogen storage and increased the rate of glucose conversion into acetate and succinate 2.2-fold and 1.4-fold, respectively, reducing the succinate-to-acetate ratio. The 13C enrichment of succinate and acetate was precisely quantified by 13C-filtered spin-echo difference 1H-NMR spectroscopy. The presence of ammonia did not modify the 13C enrichment of succinate C-2 (without ammonia, 20.8%, and with ammonia, 21.6%), indicating that the isotopic dilution of metabolites due to utilization of endogenous glycogen was not affected. In contrast, the presence of ammonia markedly decreased the 13C enrichment of acetate C-2 (from 40 to 31%), reflecting enhanced reversal of the succinate synthesis pathway. The reversal of glycolysis was unaffected by the presence of ammonia as shown by 13C-NMR analysis. Study of cell extracts showed that the main pathways of ammonia assimilation in F. succinogenes were glutamate dehydrogenase and alanine dehydrogenase. Glutamine synthetase activity was not detected. Glutamate dehydrogenase was active with both NAD and NADP as cofactors and was not repressed under ammonia limitation in the culture. Glutamate-pyruvate and glutamate-oxaloacetate transaminase activities were evidenced by spectrophotometry and 1H NMR. When cells were incubated in vivo with [1-13C]glucose, only 13C-labeled aspartate, glutamate, alanine, and valine were detected. Their labelings were consistent with the proposed amino acid synthesis pathway and with the reversal of the succinate synthesis pathway.

Shift of glycolysis as a marker of sperm maturation.

The presence of glycogen-phosphorylase (A and B forms), glucose-6-phosphatase and fructose-1, 6-diphosphatase in bonnet monkey spermatozoa was determined. The process of glycolysis gradually decreased and the process of reversal of glycolysis steadily increased in monkey spermatozoa as they move from testis to caput to corpus to cauda to vas deferens and finally in ejaculate. Hence in bonnet monkeys, the functional maturity of spermatozoa and the shift in glycolysis are closely related.

Synthesis of 5-deoxy-D-xylulose-1-phosphate by human erythrocytes

Human erythrocytes synthesize 5-deoxy-D-xylulose-1-phosphate from added acetaldehyde and endogenous dihydroxyacetone phosphate. Acetaldehyde is not only a substrate for the reaction but also undergoes oxidation, causing reversal of glycolysis and thus accumulation of the product.

Reversal of glycolysis in yeast

When a buffered, aerobic suspension of ethanol-grown cells of Saccharomyces cerevisiae is treated with ethanol, a rapid flux of metabolism is observed from endogenous phosphoenolpyruvate to hexose monophosphates. Intracellular concentrations of phosphoenolpyruvate, 2-phosphoglycerate, and 3-phosphoglycerate record a monotonic drop, while those of triose phosphates and fructose 1,6-diphosphate fall after an early rise; fructose 6-phosphate, mannose 6-phosphate, and glucose 6-phosphate levels rise to a plateau. Prior growth on glucose extinguishes fructose 1,6-diphosphatase activity and completely arrests the rise of the hexose monophosphates. By using mutants blocked at a number of glycolytic steps it has been concluded that the metabolic flow takes place along the Embden-Meyerhof pathway in the reverse direction bypassing pyruvate kinase and fructose 6-phosphate kinase. Ethanol acts as a trigger by supplying NADH at the glyceraldehyde 3-phosphate dehydrogenase step. The rate of the reversal in the span phosphoenolpyruvate to fructose 1,6-diphosphate approaches 40 μ mol of 3-carbon units per minute per gram of wet cells. The in vivo activity of fructose 1,6-diphosphatase is nearly a quarter of this rate.

Lipid and sugar metabolism during the afterripening of sour cherry embryos

Stored lipid decreased in cotyledons of afterripening seed of sour cherry (Prunus cerasus L.). The lipid apparently is degraded to acetate and metabolized by the glyoxylate cycle and reversal of glycolysis to free sugars, which are then transported to the embryonic axis, the major site of respiration during afterripening. The provision of substrate allows for activation of the pentose phosphate cycle, an increased respiratory rate of this tissue, and production of the necessary intermediates for synthesis of essential structural elements necessary for the germination process.

Carbon dioxide fixation in green sulphur bacteria.

1. About one-third of the CO(2) fixed during photosynthesis by washed suspensions of Chlorobium thiosulfatophilum strain 8346 gave rise to alpha-oxoglutarate and branched-chain oxo acids, mainly beta-methyl-alpha-oxovalerate. Another one-third to one-half gave rise to a polyglucose. 2. The fixation of CO(2) was inhibited by fluoroacetate, increasing concentrations up to 1mm stimulating the accumulation of alpha-oxoglutarate and causing a decrease in the formation of the branched-chain oxo acids and polyglucose. 3. Acetate was converted into the same products as was CO(2). 4. Fluoroacetate (1mm) had a negligible effect on the formation of polyglucose from acetate and caused a slight inhibition of the formation of the branched-chain oxo acids and increased accumulation of alpha-oxoglutarate. 5. Iodoacetate (1mm) strongly inhibited polyglucose formation from acetate and caused accumulation of pyruvate. The formation of the branched-chain oxo acids from acetate was only slightly affected by this inhibitor. 6. Pyruvate can be metabolized by this organism in the presence of a suitable electron donor whether CO(2) is present or not. In the absence of CO(2) pyruvate is converted into polyglucose. 7. The accumulation of oxo acids during CO(2) fixation is completely inhibited by NH(4) (+) ions. The formation of the branched-chain oxo acids is considerably decreased by the presence of isoleucine, leucine or valine, or a mixture of these. 8. CO(2) fixation in two other strains of Chlorobium appears to exhibit a similar pattern to that in C. thiosulfatophilum strain 8346. 9. It is concluded that in washed suspensions, CO(2) is fixed mainly by a mechanism involving the reductive carboxylic acid cycle. Acetate, the product of the cycle, is converted into polyglucose via pyruvate synthase and a reversal of glycolysis or into branched-chain oxo acids by an unknown mechanism.

The reversal of glycolysis in rat epididymal adipose tissue

The reversal of glycolysis in rat epididymal adipose tissue

Untersuchungen zum Mechanismus der Biosynthese von Cladinose und Desosamin mit Hilfe von D-Glucose-[U-14C-4-T

The mechanism of the biosynthesis of L-cladinose (I) and D-desosamine (II) was investigated with the aid of D-glucose- [U-14C-4-T] (III). When III was added to cultures of S. erythreus the T/14C ratio in I and II (isolated from erythromycin) was 38 to 74 per cent lower than in III. This loss of tritium could occur by: 1. The formation of exchangeable hydrogen during the reaction; 2. an intramolecular isotope effect; 3. partial degradation of the glucose and resynthesis by reversal of glycolysis, in which case the tritium at C-4 would be lost. As was shown by degradation neither cladinose nor desosamine contained tritium at C-6. Therefore an intramolecular hydrogen transfer from C-4 to C-6 such as that postulated in the biosynthesis of 6-deoxysugars could not be demonstrated. In both cladinose and desosamine all the tritium is very probably located at C-4. Therefore if a nucleotide bound 4-keto-6-deoxyhexose occurs as an intermediate as in the biosynthesis of 6-deoxy- and 3,6-dideoxysugars the tritium which is removed from the 4-position in this step must be reintroduced in this position in a later step.

Study on the glyoxylate cycle in germinating sesame seed embryos

The glyoxylate-cycle system in germinated sesame seed embryos was examined from several viewpoints. This glyoxylate-cycle system was found in the mitochondrial fraction of germinated sesame seed embryos, and it also was found that this cycle should predominate over the TCA-cycle system in seed mitochondria during the germination, although the mitochondrial fraction of sesame seed also contained other TCA-cycle enzymes, condensing enzyme, aconitase, fumarase, etc., in addition to isocitritase and malate synthetase. The activities of both glyoxylate-cycle enzymes, isocitritase and malate synthetase, were increased remarkably by the period of seed germination after radicle emergency, and reached maximum activities at near the 8th day of seed germination. From these data and other information in the literature, the glyoxylate-cycle system in sesame seed embryos should act as a plausible route for the conversion of acetate into nucleic acid by means of some modified metabolic pathway combined with reversal of glycolysis.

The oxidative pentose phosphate cycle. V. Complete oxidation of glucose 6-phosphate in a reconstructed system of the oxidative pentose phosphate cycle

1. 1. A reconstructed system consisting of purified enzymes of the pentose-P cycle has been shown to catalyze the complete oxidation of glucose-6-P. The hydrogens from reduced triphosphopyridine nucleotide were accepted either by oxidized glutathione in the presence of glutathione reductase or by molecular oxygen in the presence of old yellow enzyme. 2. 2. The ratio of reduced glutathione per mole of glucose-6-P oxidized was 21.7 or 90% of theoretical. C 14O 2 and small amounts of free glucose recovered from an experiment with uniformly C-14 labeled glucose-6-P accounted quantitatively for the amount of glucose-6-P that had disappeared. 3. 3. The oxidation of glucose via the pentose-P cycle was inhibited in the presence of a system of glycolysis. With limiting concentrations of both hexokinase and phosphofructokinase, the extent of inhibition was dependent on the amount of phosphofructokinase added. 4. 4. The interrelation between glycolysis and the pentose-P cycle is discussed and a possible role for sedoheptulosediphosphatase in the reversal of glycolysis is proposed.

Phosphorylation of Pyruvate by the Pyruvate Kinase Reaction and Reversal of Glycolysis in a Reconstructed System

Phosphorylation of Pyruvate by the Pyruvate Kinase Reaction and Reversal of Glycolysis in a Reconstructed System