Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Fructosediphosphates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,459 records · Page 81Linked to original sources
PubMed1983

The interaction of fructose 2,6-bisphosphate and AMP with rat hepatic fructose 1,6-bisphosphatase.

The binding of the inhibitory ligands fructose 2,6-bisphosphate and AMP to rat liver fructose 1,6-bisphosphatase has been investigated. 4 mol of fructose-2,6-P2 and 4 mol of AMP bind per mol of tetrameric enzyme at pH 7.4. Fructose 2,6-bisphosphate exhibits negative cooperatively as indicated by K'1 greater than K'2 greater than K'3 greater than or equal to K'4 and a Hill plot, the curvature of which indicates K'2/K'1 less than 1, K'3/K'2 less than 1, and K'4/K'3 = 1. AMP binding, on the other hand, exhibits positive cooperativity as indicated by K'1 less than K'2 less than K'3 less than K'4 and an nH of 2.05. Fructose 2,6- and fructose 1,6-bisphosphates enhance the binding of AMP as indicated by an increase in the intrinsic association constants. At pH 9.2, where fructose 2,6-bisphosphate and AMP inhibition of the enzyme are diminished, fructose 2,6-bisphosphate binds with a lower affinity but in a positively cooperative manner, whereas AMP exhibits half-sites reactivity with only 2 mol of AMP bound per mol of tetramer. Ultraviolet difference spectroscopy confirmed the results of these binding studies. The site at which fructose 2,6-bisphosphate binds to fructose 1,6-bisphosphatase has been identified as the catalytic site on the basis of the following. 1) Fructose 2,6-bisphosphate binds with a stoichiometry of 1 mol/mol of monomer; 2) covalent modification of the active site with acetylimidazole inhibits fructose 2,6-bisphosphate binding; and 3) alpha-methyl D-fructofuranoside-1,6-P2 and beta-methyl D-fructofuranoside-1,6-P2, substrate analogs, block fructose 2,6-bisphosphate binding. We propose that fructose 2,6-bisphosphate enhances AMP affinity by binding to the active site of the enzyme and bringing about a conformational change which may be similar to that induced by AMP interaction at the allosteric site.

Adenosine Monophosphate↗
PubMed1982

Isolation and kinetic properties of pyruvate kinase activated by fructose-1,6-biphosphate from Salmonella typhimurium LT-2.I.

Pyruvate kinase, activated by fructose-1,6-biphosphate from Salmonella typhimurium LT-2, has been isolated and purified to homogeneity. The enzyme, similar to that from Escherichia coli, is a tetramer with an approximate molecular weight of 240,000. The native enzyme shows optimum pH 6.8 (T = 30 degrees C). The enzymatic reaction does not require K+ ions; while Mg2+ or Mn2+ are essential for its activity. The non-activated enzyme shows sigmoid kinetics to phosphoenolpyruvate with a Hill coefficient of 2.73; the activated enzyme becomes michaelian with KSADP y KSPEP 0.25 and 0.08 mM, respectively. Both substrates excess and ATP cause enzyme inhibition. In agreement with the experimental results a steady-state random-ordered hybrid Bi-Bi mechanism with two dead-end complexes is proposed.

Bacterial Proteins↗
PubMedDate not supplied

Effect of certain hexosephosphate esters on haemoglobin affinity for oxygen.

The present work is designed to establish the effect of some hexosephosphates esters on the deoxygenation capacity of haemoglobin. To this end the dissociation curves of oxyhaemoglobin in hemolysates of human erythrocyte have been determined in the presence of increasing concentrations of hexosephosphates (2.5; 5; 10 muM/g Hb). The curves appear significantly shifted to the right in the presence of fructose-1,6-diphosphate, showing its possible behaviour as an allosteric effector on the haemoglobin molecules.

Adult↗
PubMed1981

Fructose 2,6-bisphosphate. Hormonal regulation and mechanism of its formation in liver.

Vasopressin, phenylephrine, and A23187 cause an accumulation of fructose 2,6-bisphosphate in hepatocytes from fed rats, but not in Ca2+-depleted hepatocytes from fed rats or in phosphorylase kinase-deficient hepatocytes from (gsd/gsd) rats. The effect of vasopressin and phenylephrine is not found in hepatocytes from overnight-starved rats. Thus, the accumulation of fructose 2,6-bisphosphate by these agents may depend on the stimulation of glycogenolysis and on the resulting accumulation of hexose 6-phosphate. In support of this hypothesis, conditions are described for the enzymatic synthesis of fructose 2,6-bisphosphate from fructose 6-phosphate and Mg-ATP in liver extracts. Half-maximal activity (0.8 nmol/min.g) is obtained with about 60 microM fructose 6-phosphate, and the activity can be separated fom phosphofructokinase by ammonium sulfate fractionation. Treatment of rats or isolated hepatocytes with glucagon results in a 4-5-fold decrease in the maximal activity of this enzyme.

Animals↗
PubMed1982

Fructose-1,6-diphosphate (FDP), hemodynamics and heart metabolism: preliminary experimental studies.

Fructose-1,6-diphosphate (FDP) has been reported to exert beneficial effects on several cardiac functions. We studied the effects of FDP on the biochemical and dynamic functions of the heart in anesthetized dogs. Significant effects of FDP were noted mostly as related to pyruvate and lactate metabolism. The results seem to indicate that FDP may improve heart metabolism, and coronary function in restricted animals.

Animals↗
PubMed1978

Effect of a single oral dose of oxymetholone on the metabolism of human erythrocytes.

Androgenic steroids have been shown to enhance erythrocyte 2,3-DPG production in vivo and in vitro, and to stimulate the pentose shunt oxidative reactions in vitro. Furthermore, a 3 beta- and a 17 beta-hydroxysteroid dehydrogenase have been identified in red cells. The present study was carried out to explore a cumulative effect of androgens on glycolysis and androgen reduction in human erythrocytes in vivo following a single 50 mg oral dose of 17 beta-hydroxy-2 (hydroxymethylene)-17 methyl-5 alpha-androstan-3-one (oxymetholone). The rate of erythrocyte glycolysis was measured by quantitative determination of: fructose-1,6-diphosphate (FDP); dehydroxyacetone phosphate (DAP); 2,3-diphosphoglycerate (2,3-DPG); adenosine triphosphate (ATP); and lactate. Serum and erythrocyte steroids were separated by thin layer chromatography. The reduction of 5 alpha-androstan-17 beta-ol-3-one by red cell hemolysate was measured in the presence of NADPH as an index of 3(17)beta-hydroxysteroid dehydrogenase activity. Our results show that oxymetholone administration is followed by the appearance of an unidentified steroid fraction in chromatograms of serum and erythrocytes, simultaneously with the enhancement of glycolysis and of hydroxysteroid dehydrogenase activity in erythrocytes. A direct effect of androgen on erythrocyte metabolism, which is independent of the hormone erythropoietic effect, is discussed.

17-Hydroxysteroid Dehydrogenases↗
PubMed1982

Pharmacokinetics of fructose-1, 6-diphosphate in the rat.

The pharmacokinetics of fructose-1, 6-diphosphate administered to the rat by intravenous injection was studied. Labelled fructose-1, 6-diphosphate was measured in blood, where it reaches the highest amount 10 min after administration, and in different organs. Residual radioactivity was measured in organs 20 min after administration, the highest values being found in the kidney and the lowest in the brain. The hydrolytic activity of the various organs toward fructose-1, 6-diphosphate was measured in organ extracts and was found to be maximal in the kidney and minimal in the brain.

Animals↗