Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Phenazines”

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 1,027 records · Page 57Linked to original sources
PubMed2003

Evidence of cytochrome P450-catalyzed cleavage of the ether bond of phenoxybutyrate herbicides in Rhodococcus erythropolis K2-3.

Bacterial strain Rhodococcus erythropolis K2-3 can cleave the ether bond of the phenoxybutyrate herbicides, i.e., 4-(2,4-dichlorophenoxy)butyrate (2,4-DB) and 4-(4-chloro-2-methylphenoxy)butyrate (MCPB), by an enzyme system that is constitutively expressed. The enzyme(s) involved were investigated in this study. The rate of disappearance of 2,4-DB determined in a whole cell assay amounted to 0.6 mmol/h x g(dry mass). Carbon monoxide difference spectra of dithionite-reduced whole cells and crude cell extracts suggested that strain K2-3 contains a soluble cytochrome P450 (P450), named P450(PB-1). The addition of various phenoxybutyrate substrates to crude cell extracts resulted in typical difference spectra following the type I pattern of substrate binding with P450. The rate of 2,4-DB cleavage was reduced by inhibitors of P450: 5 mM metyrapone and carbon monoxide at a CO/O2 ratio of 10 reduced the activity by about 20%, and 70%, respectively. The ether cleaving activity completely disappeared after disruption of the cells and could not be detected in crude extracts. To elucidate the enzymatic basis of this reaction, P450 was partially purified. With the resulting enzyme preparation, 2,4-DB cleavage activity was re-established, becoming measurable after the addition of either phenazine methosulfate or ferredoxin and ferredoxin/NADP oxidoreductase from spinach. We detected no activities attributable to alpha-ketoglutarate-dependent dioxygenase or NAD(P)H-dependent monooxygenase. These results collectively indicate that cleavage of the ether bond of phenoxybutyrate herbicides is catalyzed by P450-mediated activity in this strain. One of the products derived from this reaction is dichlorophenol, and comparative chromatographic analyses suggest that the other product is a C4-carbonic acid, most likely succinic semialdehyde/succinate.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2004

The chemical mechanism of action of glucose oxidase from Aspergillus niger.

Glucose oxidase from Aspergillus niger (EC 1.1.3.4) is able to catalyze the oxidation of beta-D-glucose with p-benzoquinone, methyl-1,4-benzoquinone, 1,2-naphthoquinone, 1,2-naphthoquinone-4-sulfonic acid, potassium ferricyanide, phenazine methosulfate, and 2,6-dichloroindophenol. In this work, the steady-state kinetic parameters, V1/K(B), for reactions of these substrates were collected from pH 2.5-8. Further, the molecular models of the enzyme's active site were constructed for the free enzyme in the oxidized state, the complex of beta-D-glucose with the oxidized enzyme, the complex of reduced enzyme with methyl-1,4-benzoquinone, the reduced enzyme plus 1,2-naphthoquinone-4-sulfonic acid, oxidized enzyme plus reduced 1,2-naphthoquinone-4-sulfonic acid (hydroquinone anion), and oxidized enzyme plus fully reduced 1,2-naphthoquinone-4-sulfonic acid. Combining the steady-state kinetic and structural data, it was concluded that Glu412 bound to His559, in the active site of enzyme, modulates powerfully its catalytic activity by affecting all the rate constants in the reductive and the oxidative half-reaction of the catalytic cycle. His516 is the catalytic base in the oxidative and the reductive part of the catalytic cycle. It was estimated that the pKa of Glu412 (bound to His559) in the free reduced enzyme is 3.4, and the pKa of His516 in the free reduced enzyme is 6.9.

Aspergillus niger↗
PubMed1998

Histochemical determination of lactate dehydrogenase activity in rat lens; influence of different parameters.

PURPOSE: 1. To optimize a histochemical technique for the determination of lactate dehydrogenase activity in rat lens. 2. To determine the distribution of lactate dehydrogenase activity within the lens. 3. To analyse different components of variation in the method. METHODS: A total of 24 six-week-old Sprague-Dawley rats were used. Cryosections of whole eyes were incubated with different media. The influence of incubation time, pH, the concentration of dye, lactate, nicotinamide dinucleotide, phenazine methosulfate, sodium azide, hydrazine and polyvinyl alcohol on the enzyme histochemical reaction was investigated. The staining reactant was nitrobluetetrazolium and the staining density was measured with a microscope-based photometer. RESULTS: The lactate dehydrogenase activity was highest in the epithelium, followed by the nucleus, the anterior cortex, and the posterior cortex. The three largest components of variation in the analyses were rats, sections (including variation in section thickness) and density measurements (including variation within the different regions). CONCLUSION: The composition of the final incubation medium for the detection of lactate dehydrogenase activity in rat lens are similar to that shown for other tissues. Lactate dehydrogenase activity varies in different regions of the lens.

Animals↗
PubMed1999

Plants genetically modified to produce N-acylhomoserine lactones communicate with bacteria.

N-acylhomoserine lactones (AHLs) play a critical role in plant/microbe interactions. The AHL, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), induces exoenzymes that degrade the plant cell wall by the pathogenic bacterium Erwinia carotovora. Conversely, the antifungal activity of the biocontrol bacterium Pseudomonas aureofaciens 30-84 is due (at least in part) to phenazine antibiotics whose synthesis is regulated by N-hexanoylhomoserine lactone (HHL). Targeting the product of an AHL synthase gene (yenI) from Yersinia enterocolitica to the chloroplasts of transgenic tobacco plants caused the synthesis in plants of the cognate AHL signaling molecules (OHHL and HHL). The AHLs produced by the transgenic plants were sufficient to induce target gene expression in several recombinant bacterial AHL biosensors and to restore biocontrol activity to an HHL-deficient P. aureofaciens strain. In addition, pathogenicity was restored to an E. carotovora strain rendered avirulent as a consequence of a mutation in the OHHL synthase gene, carI. The ability to generate bacterial quorum-sensing signaling molecules in the plant offers novel opportunities for disease control and for manipulating plant/microbe interactions.

Bacterial Proteins↗
PubMed1980

The production of (14C) oxalate during the metabolism of (14C) carbohydrates in isolated rat hepatocytes.

Oxalate (14C) was produced during the metabolism of (U-14C) carbohydrates in hepatocytes isolated from normal rats. At 10 mM, the order of oxalate production was fructose > glycerol > xylitol > sorbitol greater than or equal to glucose in the ratio 10 : 4 : 3 : 1 : 1. This difference between oxalate production from fructose and glucose was reflected in their rates of utilisation, glucose being poorly metabolised in hepatocytes from fasted rats. Fructose was rapidly metabolised, producing glucose, lactate and pyruvate as the major metabolites. Glycerol, xylitol and sorbitol were metabolised at half the rate of fructose, the major metabolites being glucose, lactate and glycerophosphate. The marked similarity in the pattern of intermediary metabolites produced by these polyols was not, however, reflected in the rates of oxalate production. Hepatic polyol metabolism resulted in high levels of cytosolic NADH, as indicated by elevated lactate : pyruvate and glycerophosphate : dihydroxyacetone phosphate ratios. The artificial electron acceptor, phenazine methosulphate (PMS) stimulated oxalate production from the polyols, particularly xylitol. In the presence of PMS, the order of oxalate production was fructose greater than or equal to xylitol > glycerol > sorbitol in the ratio 10 : 10 : 6 : 2. The production of glucose, lactate and pyruvate from the polyols was also stimulated by PMS, whereas the general metabolism of fructose, including oxalate production, was little affected. Oxalate (14C) was produced from (1-14C), (2-14C) and (6-14C) but not (3,4-14C) glucose in hepatocytes isolated from non-fasted, pyridoxine-deficient rats. Whilst this labelling pattern is consistent with oxalate being produced by a number of pathways, it is suggested that metabolism via hydroxypyruvate is a major route for oxalate production from various carbohydrates, with perhaps the exception of xylitol, which appears to have an alternative mechanism for oxalate production. The observation that carbohydrates, particularly fructose, contribute to endogenous oxalate production lends support to the hypothesis that a high sucrose consumption contributes to the formation of renal oxalate stones in man.

Animals↗
PubMed2005

Ferroelectricity near room temperature in co-crystals of nonpolar organic molecules.

The research on ferroelectric materials-mostly inorganic compounds or organic polymers-is increasingly motivated by both basic scientific concerns and the potential for practical applications in electronics and optics. Ferroelectricity in organic solids would be important for the development of all-organic electronic and photonic devices. The conventional approach to making organic ferroelectrics is based on the use of polar molecules. Here we report that through supramolecular assembly of nonpolar conjugated molecules, a remarkable ferroelectric response can be obtained in co-crystals of low-molecular-weight organic compounds. Co-crystals of phenazine and chloranilic acid reveal large spontaneous polarization and sizable room-temperature dielectric constants exceeding 100. The present findings provide an approach to making potentially useful organic ferroelectric materials.

Journal Article↗
PubMed2004

[Ru(TAP)2(dppz)]2+: a DNA intercalating complex, which luminesces strongly in water and undergoes photo-induced proton-coupled electron transfer with guanosine-5'-monophosphate.

The lowest excited state of [Ru(TAP)2(dppz)]2+ (TAP = 1,4,5,8-tetraazaphenanthrene, dppz = dipyrido[3,2-a:2',3'-c]phenazine) 1 is strongly luminescent, even in water, and very oxidizing. Therefore it is able to oxidise not only guanosine-5'-monophosphate (GMP), as demonstrated by laser flash photolysis, but also guanine-containing polynucleotides such as calf thymus DNA and [poly(dG-dC)]2. The luminescence quenching was found to be faster in H2O than in D2O, as is the back reaction, indicating that both processes probably proceed by proton-coupled electron transfer. These properties, that are controlled by the triplet MLCT state in which the charge has been transferred from the Ru to a TAP ligand, contrast with those of the well known [Ru(phen)2(dppz)]2+ 2.

DNA↗
PubMed1965

THE EFFECT OF DIFFERENT HORMONAL CONDITIONS ON THE CONCENTRATION AND OXIDOREDUCTION STATE OF THE NICOTINAMIDE NUCLEOTIDES OF RAT LIVER.

1. The concentration and oxidoreduction state of the liver nicotinamide nucleotides of rats subjected to a number of hormonal treatments have been measured. 2. Adrenalectomy decreases the NADP(+) content by 80% but has little effect on NAD(+), NADH or NADPH. High doses of cortisone produce similar changes, but more physiological doses (5mug. daily) tend to increase the NADP(+) content. 3. Glucagon treatment of normal rats lowered the NADH and NADP(+) concentrations but did not affect the total amounts present. Growth hormone increased the concentrations and total amounts of NAD(+) and NADH but significantly decreased the concentrations and total amounts of NADP(+) and NADPH. 4. Measurements have been made of a number of enzymes in the livers of adrenalectomized and glucagon-treated rats that could affect the oxidoreduction state of NADP. The activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase are not affected by adrenalectomy or treatment with cortisone or glucagon. Nor does adrenalectomy affect the activity of NADPH-cytochrome c oxidoreductase or NADPH-glutathione oxidoreductase. The hepatic content of glutathione is, however, decreased 50% by adrenalectomy. 5. Measurements of the oxidation of [1-(14)C]glucose and [6-(14)C]glucose by liver slices from adrenalectomized rats showed that glucose oxidation was substantially normal, although phenazine methosulphate caused a smaller stimulation of the oxidation of C-1 of [1-(14)C]glucose in slices from the livers of adrenalectomized rats than it did with slices from controls. The hepatic synthesis of lipids from [1-(14)C]glucose was marginally increased in adrenalectomized rats. 6. The additional NADP(+) found when liver is extracted with 0.02n-sulphuric acid-0.1m-sodium sulphate is less affected than the NADP(+) extracted with 0.1n-hydrochloric acid in adrenalectomized or glucagon-treated rats. Hooded Norway rats appear to have less of this extra form of NADP(+) than albino rats. 7. An attempt has been made to correlate the observed changes in the nicotinamide nucleotides with metabolic patterns prevailing in different hormonal conditions.

Adrenalectomy↗
PubMed1965

The microbial oxidation of methanol. The alcohol dehydrogenase of Pseudomonas sp. M27.

1. No primary hydrogen acceptor other than phenazine methosulphate has been found for the alcohol dehydrogenase from Pseudomonas sp. M27. 2. None of a wide range of vitamins or cofactors has any effect on the activity of the enzyme. 3. The enzyme is far less sensitive to metal-chelating agents and thiol reagents than are other alcohol dehydrogenases. 4. Methanol is oxidized at least as fast as other alcohols by this enzyme and its well-defined substrate specificity is different from that of other alcohol dehydrogenases. Only primary alcohols are oxidized; the general formula for an oxidizable substrate is R.CH(2).OH, where R may be H or [Formula: see text] 5. Whole organisms oxidize only those alcohols that are oxidized by the isolated enzyme.

Alcohol Oxidoreductases↗
PubMed1969

The pentose phosphate pathway of glucose metabolism. Enzyme profiles and transient and steady-state content of intermediates of alternative pathways of glucose metabolism in Krebs ascites cells.

1. The pentose phosphate pathway in Krebs ascites cells was investigated for regulatory reactions. For comparison, the glycolytic pathway was studied simultaneously. 2. Activities of the pentose phosphate pathway enzymes were low in contrast with those of the enzymes of glycolysis. The K(m) values of glucose 6-phosphate dehydrogenase for both substrate and cofactor were about four times the reported upper limit for the enzyme from normal tissues. Fructose 1,6-diphosphate and NADPH competitively inhibited 6-phosphogluconate dehydrogenase. 3. About 28% of the hexokinase activity was in the particulate fraction of the cells. The soluble enzyme was inhibited by fructose 1,6-diphosphate and ribose 5-phosphate, but not by 3-phosphoglycerate. The behaviour of the partially purified soluble enzyme in vitro in a system simulating the concentrations of ATP, glucose 6-phosphate and P(i) found in vivo is reported. 4. Kinetics of metabolite accumulation during the transient state after the addition of glucose to the cells indicated two phases of glucose phosphorylation, an initial rapid phase followed abruptly by a slow phase extending into the steady state. 5. Of the pentose phosphate pathway intermediates, accumulation of 6-phosphogluconate, sedoheptulose 7-phosphate and fructose 6-phosphate paralleled the accumulation of glucose 6-phosphate. Erythrose 4-phosphate reached the steady-state concentration by 2min., whereas the pentose phosphates accumulated linearly. 6. The mass-action ratios of the pentose phosphate pathway reactions were calculated. The transketolase reaction was at equilibrium by 30sec. and then progressively shifted away from equilibrium towards the steady-state ratio. The glucose 6-phosphate dehydrogenase was far from equilibrium at all times. 7. Investigation of the flux of [(14)C]glucose carbon confirmed the existence of an operative pentose phosphate pathway in ascites cells, contributing 1% of the total flux in control cells and 10% in cells treated with phenazine methosulphate. 8. The pentose phosphate formed by way of the direct oxidative route and estimated from the (14)CO(2) yields represented 20% of the total accumulated pentose phosphate, the other 80% being formed by the non-oxidative reactions of the pentose phosphate pathway. 9. The pentose phosphate pathway appears to function as two separate pathways, both operating towards pentose phosphate formation. Control of the two pathways is discussed.

Adenosine Triphosphate↗
PubMed1973

Trimethylamine metabolism in obligate and facultative methylotrophs.

1. Twelve bacterial isolates that grow with trimethylamine as sole source of carbon and energy were obtained in pure culture. All the isolates grow on methylamine, dimethylamine and trimethylamine. One isolate, bacterium 4B6, grows only on these methylamines whereas another isolate, bacterium C2A1, also grows on methanol but neither grows on methane; these two organisms are obligate methylotrophs. The other ten isolates grow on a variety of C(i) and other organic compounds and are therefore facultative methylotrophs. 2. Washed suspensions of the obligate methylotrophs bacteria 4B6 and C2A1, and of the facultative methylotrophs bacterium 5B1 and Pseudomonas 3A2, all grown on trimethylamine, oxidize trimethylamine, dimethylamine, formaldehyde and formate; only bacterium 5B1 and Ps. 3A2 oxidize trimethylamine N-oxide; only bacterium 4B6 does not oxidize methylamine. 3. Cell-free extracts of trimethylamine-grown bacteria 4B6 and C2A1 contain a trimethylamine dehydrogenase that requires phenazine methosulphate as primary hydrogen acceptor, and evidence is presented that this enzyme is important for the growth of bacterium 4B6 on trimethylamine. 4. Cell-free extracts of eight facultative methylotrophs, including bacterium 5B1 and Ps. 3A2, do not contain trimethylamine dehydrogenase but contain instead a trimethylamine monooxygenase and trimethylamine N-oxide demethylase. It is concluded that two different pathways for the oxidation of trimethylamine occur amongst the isolates.

Arthrobacter↗
PubMed1975

Plastid development in primary leaves of Phaseolus vulgaris. Development of plastid adenosine triphosphatase activity during greening.

The etioplasts of dark-grown bean leaves showed ATPase (adenosine triphosphatase) activity which had a pH optimum of 8.5, was stimulated by dithiothreitol and unaffected by light-triggering. Bean chloroplasts showed a low activity of dark-induced ATPase with a pH optimum of 8.5 and a substantial amount of light-triggered activity with a pH optimum of 8.0. The light-triggered activity depended on dithiothreitol and Mg2+ and was promoted by phenazine methosulphate. Light-triggered ATPase activity was completely inhibited by 20mum-dicyclohexylcarbodi-imide. Etioplasts developed light-triggered ATPase activity in response to 30 min illumination of the etiolated leaves. During the 48 h of light-induced greening of dark-grown leaves there was a 70% increase of the chloroplast ATPase activity found after light-triggering and a 30% fall in the dark-induced activity, both expressed on a per leaf basis. As the larger part of these changes occurred during the first 30 min of illumination, it is concluded that most or all of the chloroplast ATPase was present in the etioplast, a conclusion identical with that of Lockshin et al. (1971) for maize. During 48 h of greening there was a tenfold increase in the amount of thylakoid membrane in the leaf together with an 83% fall in the ATPase activity per m2 of thylakoid membrane, measured after light-triggering.

Adenosine Triphosphatases↗
PubMed1977

Solubilization, partial purification and properties of N-methylglutamate dehydrogenase from Pseudomonas aminovorans.

1. Extracts of amine-grown Pseudomonas aminovorans contained a particle-bound N-methylglutamate dehydrogenase (EC 1.5.99.5). The enzyme was not present in succinate-grown cells, and activity appeared before growth began in succinate-grown cells which had been transferred to methylamine growth medium. 2. Membrane-containing preparations from methylamine-grown cells catalysed an N-methylglutamate-dependent uptake of O2 or reduction of cytochrome c, which was sensitive to inhibitors of the electron-transport chain. 3. N-Methylglutamate dehydrogenase activity with phenazine methosulphate or 2,6-dichlorophenol-indophenol as electron acceptor could be solubilized with 1% (w/v) Triton X-100. The solubilized enzyme was much less active with cytochrome c as electron acceptor and did not sediment in 1 h at 150000g. Solubilization was accompanied by a change in the pH optimum for activity. 4. The solubilized enzyme was partially purified by Sepharose 4B and hydroxyapatite chromatograpy to yield a preparation 22-fold increased in specific activity over the crude extract. 5. The partially-purified enzyme was active with sarcosine, N-methylalanine and N-methylaspartate as well as with N-methylglutamate. Evidence suggesting activity with N-methyl D-amino acids as well as with the L-forms was obtained. 6. The enzyme was inhibited by p-chloromercuribenzoate, iodoacetamide and by both ionic and non-ionic detergents. 2-Oxoglutarate and formaldehyde were also inhibitors. 7. Kinetic analysis confirmed previous workers' observations of a group transfer (Ping Pong) mechanism. 8. Spectral observations suggested that the partially purified preparation contained flavoprotein and a b-type cytochrome. 9. The role of the enzyme in the oxidation of methylamine is discussed.

2,6-Dichloroindophenol↗
PubMed1977

The purification and properties of p-cresol-(acceptor) oxidoreductase (hydroxylating), a flavocytochrome from Pseudomonas putida.

The enzyme that catalyses the hydroxylation of the methyl group of p-cresol was purified from Pseudomonas putida. It has mol.wt. 115000 and appears to contain two subunits of equal molecular weight. One subunit is a c-type cytochrome and the other is a flavoprotein. Reduction of the cytochrome occurred on addition of substrate. The same enzyme catalyses both p-cresol hydroxylation and the further oxidation of the product, 4-hydroxybenzyl alcohol. The stoicheiometry of acceptor reduced per molecule of substrate oxidized is that for two dehydrogenation reactions. The Km for p-cresol is 7.3 x 10(-6) M and that for 4-hydroxybenzyl alcohol is 47.6 x 10(-6) M. The enzyme, which is assayed with phenazine methosulphate as electron acceptor, was stimulated by particulate material, which probably contains the acceptor in vivo.

Cresols↗
PubMed1978

The dye-linked alcohol dehydrogenase of Rhodopseudomonas acidophila. Comparison with dye-linked methanol dehydrogenases.

1. A dye-linked alcohol dehydrogenase was purified 20-fold from extracts of Rhodopseudomonas acidophila 10050 grown anaerobically in the light on methanol/HCO3-. 2. The enzyme resembled many previously reported methanol dehydrogenases from other methylotrophic organisms in coupling to phenazine methosulphate, requiring ammonia as an activator, possessing a pH optimum of 9 and a mol.wt. of approx. 116000. In many other respects the enzyme showed singular properties. 3. The stability of the enzyme under various conditions of temperature and pH was studied. 4. Primary aliphatic amines containing up to nine carbon atoms (the longest tested) were better activators than ammonia. 5. A wide range of primary alcohols and aldehydes served as substrates, with apparent Km values ranging from 57 mM for methanol to 6 micron for ethanol. 6. O2 was an inhibitor competitive with respect to the alcohol substrate. In the presence of O2, apparent Km values of 145 mM were recorded for methanol. 6. Cyanide and alphaalpha'-bipyridine were inhibitors competitive with respect to the amine activator. 7. The properties of the enzyme from Rhodopseudomonas acidophila are compared with those of similar enzymes from other organisms, and implications of the salient differences are discussed.

2,2'-Dipyridyl↗
PubMed1978

The oxidative activities of membrane vesicles from Bacillus caldolyticus. Energy-dependence of succinate oxidation.

1. The properties of membrane vesicles from the extreme thermophile Bacillus caldolyticus were investigated. 2. Vesicles prepared by exposure of spheroplasts to ultrasound contained cytochromes a, b and c, and at 50 degrees C they rapidly oxidized NADH and ascorbate in the presence of tetramethyl-p-phenylenediamine. Succinate and l-malate were oxidized more slowly, and dl-lactate, l-alanine and glycerol 1-phosphate were not oxidized. 3. In the absence of proton-conducting uncouplers the oxidation of NADH was accompanied by a net translocation of H(+) into the vesicles. Hydrolysis of ATP by a dicyclohexylcarbodi-imide-sensitive adenosine triphosphatase was accompanied by a similarly directed net translocation of H(+). 4. Uncouplers (carbonyl cyanide p-trifluoromethoxyphenylhydrazone or valinomycin plus NH(4) (+)) prevented net H(+) translocation but stimulated ATP hydrolysis, NADH oxidation and ascorbate oxidation. The last result suggested an energy-conserving site in the respiratory chain between cytochrome c and oxygen. 5. Under anaerobic conditions the reduction of cytochrome b by ascorbate (with tetramethyl-p-phenylenediamine) was stimulated by ATP hydrolysis, indicating an energy-conserving site between cytochrome b and cytochrome c. However, no reduction of NAD(+) supported by oxidation of succinate, malate or ascorbate occurred, neither did it with these substrates in the presence of ATP under anaerobic conditions, suggesting that there was no energy-conserving site between NADH and cytochrome b. 6. Succinate oxidation, in contrast with that of NADH and ascorbate, was strongly inhibited by uncouplers and stimulated by ATP hydrolysis. These effects were not observed when phenazine methosulphate, which transfers electrons from succinate dehydrogenase directly to oxygen, was present. It was concluded that in these vesicles the oxidation of succinate was energy-dependent and that the reoxidation of reduced succinate dehydrogenase was dependent on the outward movement of H(+) by the protonmotive force. 7. In support of the foregoing conclusion it was shown that the reduction of fumarate by NADH was an energy-conserving process. 8. If the activities of vesicles accurately represent those of the intact organism it appears that in B. caldolyticus the reduction of fumarate to succinate at the expense of reducing equivalents from NADH is energetically favoured over succinate oxidation even under aerobic conditions. This may be related to the need for an ample supply of succinate for haem synthesis in order to provide cytochromes for the organism.

Adenosine Triphosphate↗
PubMed1979

Stimulation of glucose transport in rat adipocytes by insulin, adenosine, nicotinic acid and hydrogen peroxide. Role of adenosine 3':5'-cyclic monophosphate.

Glucose transport into adipocytes of the rat was measured by monitoring the conversion of [1-(14)C]glucose into (14)CO(2). Glucose transport was made rate-limiting by increasing the flux through the pentose phosphate pathway with phenazine methosulphate, an agent that rapidly reoxidizes NADPH. Under these conditions, the observed rate of glucose disappearance from the incubation medium was about 20% higher than the rate of conversion of the C-1 of glucose into (14)CO(2). Apparent rates of glucose transport were significantly increased by insulin, H(2)O(2), adenosine and nicotinic acid. Stimulation of the apparent rate of glucose transport by insulin was dependent on adipocyte concentration, the hormone being most effective at relatively high cell concentrations. Adenosine and nicotinic acid further enhanced the maximum stimulation of glucose transport by insulin. Potentiation of insulin action by adenosine was more pronounced at lower cell concentrations. At relatively high cell concentrations the stimulatory action of insulin was markedly decreased by adenosine deaminase. Stimulation of apparent rates of glucose transport by the compounds noted above were antagonized by agents that increased intracellular cyclic AMP concentrations (theophylline and isoprenaline) and by dibutyryl cyclic AMP. Intracellular concentrations of cyclic AMP were significantly lowered when adipocytes were incubated with insulin, H(2)O(2), adenosine or nicotinic acid. These effects were observed under basal conditions or when intracellular cyclic AMP concentrations were elevated by theophylline or isoprenaline. On the basis of the above data, we suggest that insulin, H(2)O(2), adenosine and nicotinic acid may all stimulate glucose transport in rat adipocytes by lowering the intracellular cyclic AMP concentration. These data therefore support the hypothesis that cyclic AMP inhibits glucose transport in rat adipocytes.

Adenosine↗