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At least 19 recordsLinked to original sources
PubMed1975

The roots of bioenergetics.

Understanding metabolic energy transformation began with the realization of an 'intrusion' of phosphate into the mechanism of alcoholic fermentation. The discovery of an analogous participation of phosphate in muscle glycolysis connected the metabolic generation of energy-rich phosphate bonds fed into a common transmitter, adenosine triphosphate (ATP), with the production of mechanical energy through the finding that the phosphoryl group of creatine phosphate transferred to ATP could supply the energy for muscle contraction. In this way, a functional applicability of the energy of the phosphate bond was first shown. This observation was soon followed by the recognition that the phosphoanhydride bond of ATP provided the driving force in biosynthetic reactions; in this type of bond, metabolic energy apparently collects before it is transmitted for functional and biosynthetic use. The storage of energy in ATP was first detected in anaerobic energy-yielding reactions but soon was also found in respiratory and photosynthetic energy production. However, the mechanism by which energy derived from metabolites was converted into phosphate-bond energy in the latter processes appeared to differ from that of anaerobic energy transmission. Whereas phosphorylated compounds mediate the latter in homogeneous solutions, aerobic phosphorylation and photophosphorylation in prokaryotes seem to require special submembranous structures; and in eukaryotes, energy conversion is a function of special organelles, the mitochondria and chloroplasts. The evolutionary aspects of the transition from prokaryotes to eukaryotes are of considerable interest. In conclusion, the relevance of an apparent prokaryotic origin of the energy-transforming organelles in the eukaryotes will be commented on.

Adenosine Triphosphatases↗
PubMed1975

Energy utilization for control.

When, on addition of a suitable substrate, a chemical potential is applied to an enzymic process such as glycolysis or respiration, whether in solution or membrane-bound, all components of the process pass into a nonequilibrium state, which might be steady or non-steady and which produces the following phenomena: (1) The reactants of each enzymic reaction are displaced from their equilibrium concentration, and energy is dissipated; (2) Part of each enzyme is transferred to a transition state of its catalytic function as well as isosteric and allosteric controlling functions, displaying local and gross conformation changes, and a rate-controlling state is generated; (3) In cyclic portions of a process futile events and chemical interconversion may occur; (4) In self- and cross-coupled portions of a process, oscillation with periodic changes of states and spatial propagation as well as instabilities may be observed; (5) At each step of a process, depending on the rate of flux and the specific enzymic function, a varying proportion of the free energy changes--which are concentration-dependent and derived from the overall potential of the system-is contributed to the control of flux rates. This will be exemplified for enzymes of bioenergetic pathways.

Adenosine Triphosphate↗
PubMed1975

Multienzymic nature of pyruvate kinase during development of Hymenolepis diminuta (Cestoda).

H. diminuta at different stages of development contained as many as five pyruvate kinase isozymes. Four of these were unusually sensitive to allosteric activation by fructose-1,6-P2. One isozyme which occurred only in adults or near-adults was insensitive but had a relatively low Km. All were inhibited by ATP and Ca2+, none by alanine, and the pH optimum was unaffected by fructose-1,6-P2. The five isozymes were present in gravid or reproductively active proglottids. Two of them occurred after eight days growth in the rat intestine, and three after four days. These three were also present in the immature, anterior proglottids of adult parasites. Hexacanth larvae from gravid proglottids, as well as cysticercoids developing from these larvae in Tenebrio molitor, possessed only two isozymes. It was inferred from information on tissue concentrations of ADP, ATP, phosphoenolypyruvate (PEP) and on K0.5S and Km that competition between pyruvate kinase and PEP carboxykinase is probably controlled by fructose-1,6-P2 concentrations. Since H. diminuta is an obligatory fermenter in which gluconeogenesis is minimal, the probable function of its L-type pyruvate kinases is to control the specific composition of lactic, acetic and succinic acid mixtures that are excreted at different stages of development.

Adenosine Diphosphate↗
PubMed1975

Effect of uridine diphospho-N-acetylglucosamine and sodium salicylate on L-glutamine-D-fructose-6-phosphate aminotransferase activity from rat gastric mucosa.

Mechanisms of inhibitory action of sodium salicylate on L-glutamine-D-fructose-6-phosphate aminotransferase, prepared from rat gastric mucosa, were studied. Sodium salicylate at lower concentrations (10-20 mM) inhibited reversibly aminotransferase activity by competing with fructose-6-phosphate. At higher concentrations, sodium salicylate inactivated the enzyme irreversibly, with an inactivation rate following first-order kinetics with respect to the enzyme concentration. Uridine-5'-diphospho-N-acetylglucosamine is an endogenous feedback inhibitor. It inhibited the aminotransferase-catalyzed reaction also by competing with fructose-6-phosphate but with an inhibiting activity 1000 times that of sodium salicylate. Uridine-5'-diphospho-N-acetylglucosamine reduced the salicylate inhibition of the enzymic reaction and protected the enzyme from salicylate-induced irreversible inactivation. At a fixed concentration of uridine-5'-diphospho-N-acetylglucosamine (7x10(-6)M), an increase of salicylate concentration produced an increase in enzyme activity as compared with the control.

Animals↗
PubMed1975

Heat production and metabolism during the contraction of mammalian skeletal muscle.

Methods are described whereby initial processes of muscular contraction may be investigated in a mammalian preparation, the soleus muscle of the rat. Conditions are chosen so that recovery is avoided. An isometric tetanus is investigated and an energy balance sheet is drawn up. It is found that there is more heat evolved than can be accounted for in terms of measured chemical reaction. This discrepancy is discussed with reference to the similar results that have been obtained using frog muscle.

Adenosine Diphosphate↗
PubMed1992

pH dependence of the reverse reaction catalyzed by phosphofructokinase I from Escherichia coli: implications for the role of Asp 127.

The kinetics of the reverse reaction catalyzed by Escherichia coli phosphofructokinase, i.e., the synthesis of ATP and fructose-6-phosphate from ADP and fructose-1,6-bisphosphate, have been studied at different pH values, from pH 6 to pH 9.2. Hyperbolic saturations of the enzyme are observed for both substrates. The affinity for fructose-1,6-bisphosphate decreases with pH following the ionization of a group with a pK of 6.6, whereas the catalytic rate constant and perhaps the affinity for ADP are controlled by the ionization of a group with a pK of 6. Several arguments show that the pK of 6.6 is probably that of the carboxyl group of Asp 127, whereas the pK of 6 is tentatively attributed to the carboxyl group of Asp 103. The pK of 6.6 is assigned to the carboxyl group of Asp 127 in the free enzyme, and a simple model suggests that the same group would have an abnormally high pK, above 9.6, in the complex between phosphofructokinase and fructose-1,6-bisphosphate. It is proposed that the large pK shift of more than 3 pH units upon binding of fructose-1,6-bisphosphate is due to an electrostatic repulsion that could exist between the 1-phosphate group and the carboxyl group of Asp 127, which are close to each other in the crystal structure of phosphofructokinase (Shirakihara, Y. & Evans, P.R., 1988, J. Mol. Biol. 204, 973-994). The same interpretation would also explain the much higher affinity of the enzyme for fructose-1,6-bisphosphate when Asp 127 is protonated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1992

Analysis of glucose repression in Saccharomyces cerevisiae by pulsing glucose to a galactose-limited continuous culture.

In this study, glucose repression in Saccharomyces cerevisiae was analysed under defined physiological conditions, at both the molecular and physiological levels, by pulsing glucose to a galactose-limited continuous culture. During this pulse of glucose, the galactose feed was kept constant. Directly after the glucose pulse, carbon dioxide production increased while oxygen consumption remained constant, demonstrating that the surplus of glucose had been consumed by means of fermentation. The direct accumulation of galactose in the medium after the glucose pulse indicated that the consumption of galactose had been stopped instantaneously. Galactose uptake experiments revealed that the galactose transporter was still present but apparently was incapable of galactose uptake, which could be due to inhibition of the galactose transporter by glucose. The total concentration of cAMP increased from 5 nmol g-1 at t = 0 to 25 nmol g-1 at t = 1.5 min. After 2 min the concentration of cAMP gradually decreased again to the normal level. Within 2 min after the addition of glucose, the transcription of the GAL genes and SUC2 was inhibited. In addition, the transcription of the HXK1 gene, encoding hexokinase isoenzyme 1, was also inhibited, which demonstrates that the HXK1 gene is regulated at the transcriptional level comparable with invertase.

Adenosine Triphosphate↗
PubMed1992

Dual anomeric specificity of phosphomannoisomerase assessed by 2D phase sensitive 13C EXSY NMR.

The reversible conversion between D-mannose 6-phosphate and D-fructose 6-phosphate catalyzed by yeast phosphomannoisomerase was studied by phase sensitive 2D 13C-(1H) EXSY NMR spectroscopy at 100.623 MHz, using 13C enriched substrates in the C2 position of the D-hexose 6-phosphates. The unique pair of isomerization cross-peaks observed in the 2D EXSY map correlates the 13C2 resonances of the beta-anomers of both D-[2-13C]-mannose 6-phosphate and D-[213C]-fructose 6-phosphate. This indicates that phosphomannoisomerase specifically catalyzes the reversible conversion between beta-D-mannose 6-phosphate and beta-D-fructose 6-phosphate. Since phosphoglucoisomerase was recently found to catalyze specifically the interconversion of alpha-D-glucose 6-phosphate and beta-D-fructose 6-phosphate, the beta-anomer of the ketohexose ester could be directly channeled in a multi-enzyme system involving phosphoglucoisomerase, phosphomannoisomerase and phosphofructokinase.

Fructosephosphates↗
PubMed1976

Purification and properties of two fructose-6-phosphate phosphoketolases in Bifidobacterium.

Fructose-6-phosphate phosphoketolase was purified from type strains of two species of the genus Bifidobacterium: B. globosum and B. dentium. The first species has a preferred "animal" habitat, like feces of animals and rumen of cattle; the latter is harboured in "human" habitat, like feces and dental caries of man. Two electrophoretic types of phosphoketolase (F6PPK) were previously distinguished and called "animal" and "human" type according to the habitat of the bifid organism. The purified preparations of these two phosphoketolases displayed very different optimum pH range, metal activator and molecular weight; outstanding difference was found in the substrate specificity: the enzyme from B. globosum was able to split xylulose-5-P as well as fructose-6-P, whereas the phosphoketolase from B. dentium appeared to be specific for fructose-6-P.

Actinomycetales↗
PubMed1975

Allosteric activation and competitive inhibition of yeast phosphofructokinase by d-fructose.

Purified phosphofructokinase from bakers yeast is activated by D-fructose in low concentrations (up to 1 mM) and inhibited by high concentrations. The stimulatory effect of D-fructose is similar, but smaller than that of AMP. In the presence of AMP (0.4 mM or higher) D-fructose does no longer stimulate, but its inhibitory effect persists (KI = 8 mM). Its dualistic action on phosphofructokinase activity indicates that D-fructose might induce low frequency in glycolytic oscillations by direct interaction with the enzyme.

Adenosine Monophosphate↗
PubMed1975

Enzymes of D-fructose catabolism in species of Beneckea and Photobacterium.

Cell-free extracts of strains representative of the genera Beneckea and Photobacterium catalyzed a P-enolpyruvate dependent phosphorylation of D-fructose. The resulting product, fructose-1-P, was converted to fructose-1,6-P2 by 1-P-fructokinase. Both activities were inducible, being present in D-fructose-grown cells and reduced or absent in D-gluconate-(or succinate-) grown cells.

Adenosine Triphosphate↗
PubMed1977

Different degradation pathways for glucose and fructose in Rhodopseudomonas capsulata.

In Rhodopseudomonas capsulata the enzymes of the Entner-Doudoroff pathway and the Embden-Meyerhof pathway have been examined. Fructose-grown cells contained inducible activities of phosphoenolpyruvate-fructosephospho-transferase and 1-phosphofructokinase and only low levels of fructokinase and 6-phosphofructokinase. Although fructose-grown cells contained, in addition, all the enzymes of the Entner-Doudoroff pathway together with fructose-1,6-diphosphatase and phosphoglucose isomerase, the Entner-Doudoroff pathway was not operative in fructose catabolism and served only the degradation of glucose. The functional separation of glucose and fructose catabolism via the Entner-Doudoroff and a modified Embden-Meyerhof pathway, respectively, was confirmed by different approaches: 1. Radiorespirometric experiments with glucose and fructose labelled in positions 1, 2, 3, 3+4 and 6 have been carried out. The pattern of 14CO2-evolution from position-labelled glucose was characteristic for the Entner-Doudoroff pathway, that from position-labelled fructose for the Embden-Meyerhof pathway. 2. In the presence of arsenite up to 50% of glucose- and fructose-carbon was excreted as pyruvate. Using 1-14C-glucose, 86% of the pyruvate was labelled in the carboxyl group, whereas using 1-14C-fructose only 19% of the pyruvate was labelled in the carboxyl group. 3. A glucose-6-phosphate dehydrogenase-deficient mutant was isolated which lacked a functional Entner-Doudoroff pathway but which was unaltered in its ability to grow on fructose.

Fructose↗
PubMed1977

Comparative studies of lactic acid dehydrogenases in lactic acid bacteria. I. Purification and kinetics of the allosteric L-lactic acid dehydrogenase from Lactobacillus casei ssp. casei and Lactobacillus curvatus.

The stability, pH-dependence and kinetic properties of the Mn2+ and FDP-activated NAD-dependent lactic acid dehydrogenases from Lactobacillus casei ssp. casei (ATCC 393) and L. curvatus (DSM 20010) were studied after the enzymes were purified to homogeneity by affinity chromatography. Both enzymes are virtually unidirectional, catalysing efficiency only the reduction of pyruvate. They are similar with respect to the effector requirement and pH-optimum. They differ, however, in their electrophoretic mobility, heat stability, pH-dependence of the Mn2+ requirement and several kinetic properties. It is suggested that most of these differences are caused by differences of the negative charges in the vicinity of the FDP-binding site or the site responsible for the interaction of the subunits of the enzymatically active oligomeres.

Allosteric Regulation↗
PubMed1977

Fructose metabolism in four Pseudomonas species.

1. ATP-Dependent phosphorylation of fructose could not be detected in extracts of fructose-grown cells of Pseudomonas extorquens strain 16, Pseudomonas 3A2, Pseudomonas acidovorans and Pseudomonas fluorescens. Instead, phosphorylation of fructose to fructose-1-phosphate was found to occur when cell-free extracts were incubated with fructose and phosphoenolpyruvate. Such an activity could not be detected in cell-free extracts of succinate-grown cells. 2. High levels of 1-phosphofructokinase were found in extracts of the above organisms when growth on fructose. 3. Mutants of Pseudomonas extorquens strain 16 lacking 1-phosphofructokinase were unable to grow on fructose. Revertants to growth on fructose had regained the capacity to synthesize this enzyme, indicating its necessary involvement in fructose metabolism. 4. A survey has been carried out of enzymes involved in carbohydrate metabolism in the species listed above.

Cell-Free System↗
PubMed1975

Catabolism of D-fructose and D-ribose by Pseudomonas doudoroffii. I. Physiological studies and mutant analysis.

Pseudomonas doudoroffii, a strict aerobe of marine origin, was able to utilize fructose and ribose but not glucose, gluconate, or other hexoses, pentoses, or sugar alcohols as sole sources of carbon and energy. Evidence was presented indicating that in this organism fructose was utilized via an inducible P-enolpyruvate: fructose phosphotransferase system (FPTS) which catalyzed the phosphorylation of fructose in the 1 position. The resulting fructose-1-P (F-1-P) was converted to fructose-1,6-P2 (FDP) by means of an inducible 1-P-fructokinase (1-PFK). The subsequent conversion of FDP to pyruvate involved enzymes of the Embden-Meyerhof pathway (EMP) which, with the exception of glyceraldehyde-3-P dehydrogenase (G3PDH), were constitutive. Two G3PDH activities were detected, one of which was inducible and NAD-dependent while the other was constitutive and NADP-dependent. Cell-free extracts of P. doudoroffii also contained enzymes of the methylglyoxal pathway (MGP) which converted dihydroxyacetone-P to pyruvate. The low specific activities of enzymes of this pathway as compared to the EMP suggested that the major route of FDP catabolism was via the latter pathway. 2. Ribose catabolism appeared to involve an inducible uptake system and an inducible ribokinase, the resulting ribose-5-P being converted to glyceraldehyde-3-P and fructose-6-P (F-6-P) by means of constitutive activities of the pentose-P pathway. The F-6-P formed as a result of these reactions was converted to FDP by means of a constitutive 6-P-fructokinase (6-PFK). Since no activity converting fructose or F-1-P to F-6-P could be detected in cell-free extracts of P. doudoroffii, the results suggested that fructose and ribose were catabolized via 1-PFK and 6-PFK, respectively, the two pathways converging at the level of FDP. Further evidence for this suggestion was obtained from a mutant which lacked an NAD-dependent G3PDH, accumulated FDP from both fructose and ribose, and was not able to grow on either of these compounds. 3. Ribose grown cells had increased amounts of the fructose uptake system and 1-PFK suggesting that a compound (or compounds) common to the catabolism of both fructose and ribose acted as the inducer(s) of these activities. Evidence was presented suggesting that the probable inducer(s) of 1-PFK and FPTS could be FDP, glyceraldehyde-3-P, or dihydroxyacetone-P. 4. A mutant unable to grow on fructose was characterized and found to lack FPTS while retaining 1-PFK and other enzyme activities of the EMP and MGP, indicating that a functional FPTS was essential for growth on fructose and suggesting that all or most of this sugar was catabolized via F-1-P.

Dihydroxyacetone Phosphate↗
PubMed1975

Catabolism of D-fructose and D-ribose by Pseudomonas doudoroffii. II. Properties of 1-phosphofructokinase and 6-phosphofructokinase.

1. The 1-P-fructokinase (1-PFK) and 6-P-fructokinase (6-PFK) from Pseudmonas doudoroffii were partially purified by a combination of (NH4)2SO4 fractionation and DEAE-Sephadex column chromatography. The pH optima of these enzymes were 9.0 and 8.5, respectively. 2. When the concentrations of the substrates of the 1-PFK reaction were varied, Michaelis-Menten kinetics were observed. The Kms for D-fructose-1-P (F-1-P) and ATP were 3.03 X 10(-4) M and 3.39 X 10(-4) M, respectively. Variation of MgCl2 at fixed concentrations of F-1-P and ATP resulted in sigmoidal kinetics; about 10 mM MgCl2 was necessary for maximal activity. Activity of 1-PFK was inhibited when the ratio of ATP:Mg++ was higher than 0.5, suggesting that ATP:2Mg++ was the substrate and that free ATP was inhibitory. Although an absolute requirement for K+ or NH4+ could not be demonstrated, these cations stimulated the rate of the reaction. Activity of 1-PFK was not significantly affected by 3 mM AMP, cyclic-AMP, Pi, D-fructose-6-P (F-6-P), ADP, P-enolpyruvate (PEP), pyruvate, citrate, or L-gluamate. 3. Sigmoidal kinetics were observed for 6-PFK when the concentration of F-6-P was increased and the level of ATP was kept constant. Activity of 6-PFK was increased by ADP, inhibited by PEP, and unaffected by 3 mM AMP, cyclic-AMP, Pi, F-1-P, pyruvate, or citrate.

Adenosine Triphosphate↗
PubMed1975

Purification and properties of a fructose-1,6-diphosphate activated L-lactate dehydrogenase from Staphylococcus epidermidis.

L-(+)-lactate dehydrogenase (LDH) from Staphylococcus epidermidis ATCC 14990 was purified by affinity chromatography. The purified enzyme was specifically activated by fructose-1,6-diphosphate (FDP). The concentration of FDP required for 50% maximal activity was about 0.15 mM. The enzyme activity was inhibited by adenosine diphosphate (ADP) and oxamate. The inhibition by ADP appeared to be competitive with respect to reduced nicotinamide adenine dinucleotide (NADH). The catalytic activity of the LDH for pyruvate reduction exhibited an optimum at pH 5.6. The enzyme is composed of four, probably identical, subunits. Sephadex gel filtration and sedimentation velocity at pH 5.6 Yielded molecular weights of about 130 000 and 126 000, respectively. The molecular weight at pH 6.5 and 7.0 was found to be only about 68 000. Polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate and sedimentation velocity at pH 2.0 or 8.5 revealed monomeric subunits with an approximate molecular weight of 36000. The thermostability of the heat labile enzyme was increased in the presence of FDP, NADH and pyruvate. The purified LDH exhibited an anomalous type of kinetic behavior. Plots of initial velocity vs. different concentrations of pyruvate, NADH or FDP led to saturation curves with intermediary plateau regions. As a consequence of these plateau regions the Hill coefficient alternated between lower and higher n-values. Some distinguishing properties of the S. epidermidis LDH and other LDHs activated by FDP are discussed.

Adenine Nucleotides↗