Calorimetric study of smectic polymorphism in octyloxyphenyl-nitrobenzoyloxy benzoate + decyloxyphenyl-nitrobenzoyloxy benzoate mixtures.
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Journal Article↗
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CLINICAL AND EXPERIMENTAL STUDIES ON SODIUM BENZOATE: The Value of the Sodium Benzoate Test of Renal Function, and the Effect of Injury of the Liver on Hippuric Acid Synthesis.
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Journal Article↗
Disposition of sodium benzoate in newborn infants with hyperammonemia.
Sodium benzoate lowers serum ammonia concentrations by the activation of a non-urea cycle pathway of ammonia removal. The disposition of sodium benzoate was monitored in four hyperammonemic newborn infants, using a simple and newly developed assay for benzoate and hippurate, to assess (1) the metabolic capability of patients of this age to utilize this pathway for nitrogen removal, (2) the potential risks of benzoate toxicity at clinically achieved serum benzoate concentrations, and (3) the value of routine monitoring of serum benzoate concentrations in this patient population. In three of the four infants, more than half of the administered benzoate was converted to hippurate. Hippurate was effectively cleared by the neonatal kidney, although removal of unconjugated benzoate by peritoneal dialysis or urinary excretion was slow compared with the metabolic conversion to hippurate. There was a considerable interpatient variability in benzoate metabolism; consequently, an eight-fold range in serum benzoate concentrations (2.14 to 16.0 mM/L) was found after patients had received benzoate for longer than 24 hours. These serum benzoate concentrations were calculated to be capable of producing substantial (four to 25 times) increases in free bilirubin concentrations in jaundiced infants. Although sodium benzoate offers considerable promise for the treatment of hyperammonemia, toxicity appears likely in some infants receiving this drug in currently recommended doses. Monitoring of serum concentrations appears to be warranted. Dosage reduction in jaundiced infants and in those with demonstrated insufficiency of benzoate metabolism is recommended.
Ammonia↗
The role of benzoate in anaerobic degradation of terephthalate.
The effects of acetate, benzoate, and periods without substrate on the anaerobic degradation of terephthalate (1, 4-benzene-dicarboxylate) by a syntrophic methanogenic culture were studied. The culture had been enriched on terephthalate and was capable of benzoate degradation without a lag phase. When incubated with a mixture of benzoate and terephthalate, subsequent degradation with preference for benzoate was observed. Both benzoate and acetate inhibited the anaerobic degradation of terephthalate. The observed inhibition is partially irreversible, resulting in a decrease (or even a complete loss) of the terephthalate-degrading activity after complete degradation of benzoate or acetate. Irreversible inhibition was characteristic for terephthalate degradation only because the inhibition of benzoate degradation by acetate could well be described by reversible noncompetitive product inhibition. Terephthalate degradation was furthermore irreversibly inhibited by periods without substrate of only a few hours. The inhibition of terephthalate degradation due to periods without substrate could be overcome through incubation of the culture with a mixture of benzoate and terephthalate. In this case no influence of a period without substrate was observed. Based on these observations it is postulated that decarboxylation of terephthalate, resulting in the formation of benzoate, is strictly dependent on the concomitant fermentation of benzoate. In the presence of higher concentrations of benzoate, however, benzoate is the favored substrate over terephthalate, and the culture loses its ability to degrade terephthalate. In order to overcome the inhibition of terephthalate degradation by benzoate and acetate, a two-stage reactor system is suggested for the treatment of wastewater generated during terephthalic acid production.
Acetates↗
Interspecies acetate transfer influences the extent of anaerobic benzoate degradation by syntrophic consortia.
Benzoate degradation by an anaerobic, syntrophic bacterium, strain SB, in coculture with Desulfovibrio sp. strain G-11 reached a threshold value which depended on the amount of acetate added and ranged from about 2.5 to 29.9 (mu)M. Increasing acetate concentrations also uncompetitively inhibited benzoate degradation. The apparent V(infmax) and apparent K(infm) for benzoate degradation decreased with increasing acetate concentration, but the benzoate degradation capacities (V(infmax)/K(infm)) of cell suspensions remained comparable. The addition of an acetate-using bacterium to cocultures after the threshold was reached resulted in the degradation of benzoate to below the detection limit. Mathematical simulations showed that the benzoate threshold was not predicted by the inhibitory effect of acetate on benzoate degradation kinetics. With nitrate instead of sulfate as the terminal electron acceptor, no benzoate threshold was observed in the presence of 20 mM acetate even though the kinetics of benzoate degradation were slower with nitrate rather than sulfate as the electron acceptor. When strain SB was grown with Desulfovibrio sp. strain DG2 that had a fourfold-lower V(infmax) for hydrogen use than strain G-11, the V(infmax) for benzoate degradation was 37-fold lower than that of strain SB-G-11 cocultures. The Gibb's free energy for benzoate degradation was less negative in cell suspensions with a threshold than in suspensions without a threshold. These studies showed that the threshold was not a function of the inhibition of benzoate degradation by acetate or the toxicity of the undissociated form of acetate. Rather, a critical or minimal Gibb's free energy may exist where thermodynamic constraints preclude further benzoate degradation.
Journal Article↗
Benzoate-coenzyme A ligase from Thauera aromatica: an enzyme acting in anaerobic and aerobic pathways.
In the denitrifying member of the beta-Proteobacteria Thauera aromatica, the anaerobic metabolism of aromatic acids such as benzoate or 2-aminobenzoate is initiated by the formation of the coenzyme A (CoA) thioester, benzoyl-CoA and 2-aminobenzoyl-CoA, respectively. Both aromatic substrates were transformed to the acyl-CoA intermediate by a single CoA ligase (AMP forming) that preferentially acted on benzoate. This benzoate-CoA ligase was purified and characterized as a 57-kDa monomeric protein. Based on V(max)/K(m), the specificity constant for 2-aminobenzoate was 15 times lower than that for benzoate; this may be the reason for the slower growth on 2-aminobenzoate. The benzoate-CoA ligase gene was cloned and sequenced and was found not to be part of the gene cluster encoding the general benzoyl-CoA pathway of anaerobic aromatic metabolism. Rather, it was located in a cluster of genes coding for a novel aerobic benzoate oxidation pathway. In line with this finding, the same CoA ligase was induced during aerobic growth with benzoate. A deletion mutant not only was unable to grow anaerobically on benzoate or 2-aminobenzoate, but also aerobic growth on benzoate was affected. This suggests that benzoate induces a single benzoate-CoA ligase. The product of benzoate activation, benzoyl-CoA, then acts as inducer of separate anaerobic or aerobic pathways of benzoyl-CoA, depending on whether oxygen is lacking or present.
Aerobiosis↗
[Effect of estradiol benzoate on the heat shock protein 70, 90 expressions in endometrial glandular epithelial cell].
OBJECTIVE: To explore the effect of estradiol benzoate on the expressions of heat shock protein (HSP) 70, 90 in endometrial glandular epithelial cell. METHODS: Normal endometrial glandular epithelial cells were isolated, and cultured by enzymolysis method and identified by electron microscopy and immunohistochemical analysis. The normal endometrial glandular epithelial cells were treated with culture medium only, estradiol benzoate (10(-9), 10(-8), 10(-7) or 10(-6) mol/L), estradiol benzoate (10(-9), 10(-8), 10(-7) or 10(-6) mol/L) and antiestrogen ICI 182780 (fulvestrant, faslodex, 1 micromol/L) and ICI 182780 only for 6, 12, 18, 24 hours respectively. The dose- and time-related effect of estradiol benzoate and ICI 182780 on the cell growth was measured by mononuclear cell direct cytotoxicity assay (methyl thiazolyl tetrazolium assay), and that on the expression of HSP70 and HSP90 in normal endometrial glandular epithelial cell in vitro was measured by immunohistochemical analysis and computerized image analysis system. RESULTS: Estradiol benzoate stimulated cell growth in a time- and dose-dependent manner and the effect was attenuated by the antiestrogen ICI 182780. The average cell growth rates of 10(-9), 10(-8), 10(-7), 10(-6) mol/L estradiol benzoate for 24 hours were (170 +/- 9)%, (207 +/- 11)%, (231 +/- 12)%, (257 +/- 10)%, which were significantly higher than those of 6 hours [(117 +/- 13)%, (129 +/- 10)%, (146 +/- 10)%, (176 +/- 6)%, P < 0.05] and that those estradiol + ICI 182780 for 24 hours [(137 +/- 4)%, (145 +/- 10)%, (151 +/- 9)%, (167 +/- 3)%, P < 0.05]. Estradiol benzoate treatment resulted in a time- and dose-dependent increase of the expression of HSP90 and decrease of HSP70 in human endometrial glandular epithelial cell. The expression of HSP90 in 10(-9), 10(-8), 10(-7), 10(-6) mol/L estradiol benzoate for 24 hours were (64.8 +/- 10.7)%, (75.9 +/- 12.6)%, (80.4 +/- 8.2)%, (83.2 +/- 7.6)%, which were significantly higher than that of the control [(28.0 +/- 3.3)%, (29.0 +/- 5.6)%, (29.0 +/- 5.0)%, (30.0 +/- 6.4)%, P < 0.05] and that of estradiol benzoate + ICI 182780 for 24 hours [(28.2 +/- 2.1)%, (29.7 +/- 3.2)%, (35.0 +/- 4.7)%, (34.7 +/- 6.5)%, P < 0.05]. The expression of HSP70 in 10(-9), 10(-8), 10(-7), 10(-6) mol/L estradiol benzoate for 24 hours were (38.4 +/- 5.7)%, (35.3 +/- 4.9)%, (32.5 +/- 3.1)%, (25.3 +/- 6.2)%, which were significantly lower than that of the control. The estradiol benzoate-induced effects on HSP70 levels were not attenuated by the antiestrogen ICI 182780. CONCLUSIONS: The effects of estradiol benzoate on the cell growth and HSP90 expression are estrogen receptor-dependent and the expression of HSP90 may be beneficial to the cell growth. The effect of estradiol on the expression of HSP70 is estrogen receptor-independent and the expression of HSP70 may protect the cell from damage.
Cell Proliferation↗
Benzoate fermentation by the anaerobic bacterium Syntrophus aciditrophicus in the absence of hydrogen-using microorganisms.
The anaerobic bacterium Syntrophus aciditrophicus metabolized benzoate in pure culture in the absence of hydrogen-utilizing partners or terminal electron acceptors. The pure culture of S. aciditrophicus produced approximately 0.5 mol of cyclohexane carboxylate and 1.5 mol of acetate per mol of benzoate, while a coculture of S. aciditrophicus with the hydrogen-using methanogen Methanospirillum hungatei produced 3 mol of acetate and 0.75 mol of methane per mol of benzoate. The growth yield of the S. aciditrophicus pure culture was 6.9 g (dry weight) per mol of benzoate metabolized, whereas the growth yield of the S. aciditrophicus-M. hungatei coculture was 11.8 g (dry weight) per mol of benzoate. Cyclohexane carboxylate was metabolized by S. aciditrophicus only in a coculture with a hydrogen user and was not metabolized by S. aciditrophicus pure cultures. Cyclohex-1-ene carboxylate was incompletely degraded by S. aciditrophicus pure cultures until a free energy change (DeltaG') of -9.2 kJ/mol was reached (-4.7 kJ/mol for the hydrogen-producing reaction). Cyclohex-1-ene carboxylate, pimelate, and glutarate transiently accumulated at micromolar levels during growth of an S. aciditrophicus pure culture with benzoate. High hydrogen (10.1 kPa) and acetate (60 mM) levels inhibited benzoate metabolism by S. aciditrophicus pure cultures. These results suggest that benzoate fermentation by S. aciditrophicus in the absence of hydrogen users proceeds via a dismutation reaction in which the reducing equivalents produced during oxidation of one benzoate molecule to acetate and carbon dioxide are used to reduce another benzoate molecule to cyclohexane carboxylate, which is not metabolized further. Benzoate fermentation to acetate, CO(2), and cyclohexane carboxylate is thermodynamically favorable and can proceed at free energy values more positive than -20 kJ/mol, the postulated minimum free energy value for substrate metabolism.
Acetates↗
The influence of functionality on the adsorption of p-hydroxy benzoate and phthalate at the hematite-electrolyte interface.
Kinetics of adsorption of p-hydroxy benzoate and phthalate on hematite-electrolyte interface were investigated at a constant ionic strength, I = 5 x 10(-4) mol dm(-3), pH 5 and at three different temperatures. The state of equilibrium for the adsorption of p-hydroxy benzoate onto hematite surfaces was attained at 70 h, whereas it was 30 h for phthalate-hematite system. None of the three kinetics models (Bajpai, pseudo first order and pseudo second order) is applicable in the entire experimental time period; however, the pseudo second order kinetics model is considered to be better than the pseudo first order kinetics model in estimating the equilibrium concentration both the p-hydroxy benzoate-hematite and phthalate-hematite systems. The variation of adsorption density of p-hydroxy benzoate and phthalate onto hematite surfaces as a function of concentration of adsorbate was studied over pH range 5-9 at a constant ionic strength, I = 5 x 10(-4) mol dm(-3) and at constant temperature. The adsorption isotherms for both the systems were Langmuir in nature and the maximum adsorption density (Gamma(max)) of p-hydroxy benzoate is approximately 1.5 times more than that of phthalate on hematite at pH 5 and 30 degrees C in spite of an additional carboxylic group at ortho position in phthalate. This is due to the more surface area coverage by phthalate than that of p-hydroxy benzoate on hematite surface. The activation energy was calculated using Arrhenius equation and the activation energy for adsorption of p-hydroxy benzoate at hematite-electrolyte interface is approximately 1.8 times more than that of phthalate-hematite system. The negative Gibbs free energy indicates that the adsorption of p-hydroxy benzoate and phthalate on hematite surfaces is favourable. The FTIR spectra of p-hydroxy benzoate and phthalate after adsorption on hematite surfaces were recorded for obtaining the bonding properties of adsorbates. The phenolic nu(CO) appears at approximately 1271 cm(-1) after adsorption of p-hydroxy benzoate on hematite surfaces, which shifted by 10 cm(-1) to higher frequency region. The phenolic group is not deprotonated and is not participating in the surface complexation. The shifting of the nu(as)(COO-) and nu(s)(COO-) bands and non-dissolution of hematite suggest that the p-hydroxy benzoate and phthalate form outer-sphere surface complex with hematite surfaces in the pH range of 5-7.
Journal Article↗
New aerobic benzoate oxidation pathway via benzoyl-coenzyme A and 3-hydroxybenzoyl-coenzyme A in a denitrifying Pseudomonas sp.
A denitrifying Pseudomonas sp. is able to oxidize aromatic compounds compounds completely to CO2, both aerobically and anaerobically. It is shown that benzoate is aerobically oxidized by a new degradation pathway via benzoyl-coenzyme A (CoA) and 3-hydroxybenzoyl-CoA. The organism grew aerobically with benzoate, 3-hydroxybenzoate, and gentisate; catechol, 2-hydroxybenzoate, and protocatechuate were not used, and 4-hydroxybenzoate was a poor substrate. Mutants were obtained which were not able to utilize benzoate as the sole carbon source aerobically but still used 3-hydroxybenzoate or gentisate. Simultaneous adaptation experiments with whole cells seemingly suggested a sequential induction of enzymes of a benzoate oxidation pathway via 3-hydroxybenzoate and gentisate. Cells grown aerobically with benzoate contained a benzoate-CoA ligase (AMP forming) (0.1 mumol min-1 mg-1) which converted benzoate but not 3-hydroxybenzoate into its CoA thioester. The enzyme of 130 kDa composed of two identical subunits of 56 kDa was purified and characterized. Cells grown aerobically with 3-hydroxybenzoate contained a similarly active CoA ligase for 3-hydroxybenzoate, 3-hydroxybenzoate-CoA ligase (AMP forming). Extracts from cells grown aerobically with benzoate catalyzed a benzoyl-CoA- and flavin adenine dinucleotide-dependent oxidation of NADPH with a specific activity of at least 25 nmol NADPH oxidized min-1 mg of protein-1; NADH and benzoate were not used. This new enzyme, benzoyl-CoA 3-monooxygenase, was specifically induced during aerobic growth with benzoate and converted [U-14C]benzoyl-CoA stoichiometrically to [14C]3-hydroxybenzoyl-CoA.
Acyl Coenzyme A↗
2-Hydroxycyclohexanecarboxyl coenzyme A dehydrogenase, an enzyme characteristic of the anaerobic benzoate degradation pathway used by Rhodopseudomonas palustris.
A gene, badH, whose predicted product is a member of the short-chain dehydrogenase/reductase family of enzymes, was recently discovered during studies of anaerobic benzoate degradation by the photoheterotrophic bacterium Rhodopseudomonas palustris. Purified histidine-tagged BadH protein catalyzed the oxidation of 2-hydroxycyclohexanecarboxyl coenzyme A (2-hydroxychc-CoA) to 2-ketocyclohexanecarboxyl-CoA. These compounds are proposed intermediates of a series of three reactions that are shared by the pathways of cyclohexanecarboxylate and benzoate degradation used by R. palustris. The 2-hydroxychc-CoA dehydrogenase activity encoded by badH was dependent on the presence of NAD(+); no activity was detected with NADP(+) as a cofactor. The dehydrogenase activity was not sensitive to oxygen. The enzyme has apparent K(m) values of 10 and 200 microM for 2-hydroxychc-CoA and NAD(+), respectively. Western blot analysis with antisera raised against purified His-BadH identified a 27-kDa protein that was present in benzoate- and cyclohexanecarboxylate-grown but not in succinate-grown R. palustris cell extracts. The active form of the enzyme is a homotetramer. badH was determined to be the first gene in an operon, termed the cyclohexanecarboxylate degradation operon, containing genes required for both benzoate and cyclohexanecarboxylate degradation. A nonpolar R. palustris badH mutant was unable to grow on benzoate or cyclohexanecarboxylate but had wild-type growth rates on succinate. Cells blocked in expression of the entire cyclohexanecarboxylate degradation operon excreted cyclohex-1-ene-1-carboxylate into the growth medium when given benzoate. This confirms that cyclohex-1-ene-1-carboxyl-CoA is an intermediate of anaerobic benzoate degradation by R. palustris. This compound had previously been shown not to be formed by Thauera aromatica, a denitrifying bacterium that degrades benzoate by a pathway that is slightly different from the R. palustris pathway. 2-Hydroxychc-CoA dehydrogenase does not participate in anaerobic benzoate degradation by T. aromatica and thus may serve as a useful indicator of an R. palustris-type benzoate degradation pathway.
Alcohol Oxidoreductases↗
Cloning and characterization of benzoate catabolic genes in the gram-positive polychlorinated biphenyl degrader Rhodococcus sp. strain RHA1.
Benzoate catabolism is thought to play a key role in aerobic bacterial degradation of biphenyl and polychlorinated biphenyls (PCBs). Benzoate catabolic genes were cloned from a PCB degrader, Rhodococcus sp. strain RHA1, by using PCR amplification and temporal temperature gradient electrophoresis separation. A nucleotide sequence determination revealed that the deduced amino acid sequences encoded by the RHA1 benzoate catabolic genes, benABCDK, exhibit 33 to 65% identity with those of Acinetobacter sp. strain ADP1. The gene organization of the RHA1 benABCDK genes differs from that of ADP1. The RHA1 benABCDK region was localized on the chromosome, in contrast to the biphenyl catabolic genes, which are located on linear plasmids. Escherichia coli cells containing RHA1 benABCD transformed benzoate to catechol via 2-hydro-1,2-dihydroxybenzoate. They transformed neither 2- nor 4-chlorobenzoates but did transform 3-chlorobenzoate. The RHA1 benA gene was inactivated by insertion of a thiostrepton resistance gene. The resultant mutant strain, RBD169, neither grew on benzoate nor transformed benzoate, and it did not transform 3-chlorobenzoate. It did, however, exhibit diminished growth on biphenyl and growth repression in the presence of a high concentration of biphenyl (13 mM). These results indicate that the cloned benABCD genes could play an essential role not only in benzoate catabolism but also in biphenyl catabolism in RHA1. Six rhodococcal benzoate degraders were found to have homologs of RHA1 benABC. In contrast, two rhodococcal strains that cannot transform benzoate were found not to have RHA1 benABC homologs, suggesting that many Rhodococcus strains contain benzoate catabolic genes similar to RHA1 benABC.
Base Sequence↗
Selenocysteine-containing proteins in anaerobic benzoate metabolism of Desulfococcus multivorans.
The sulfate-reducing bacterium Desulfococcus multivorans uses various aromatic compounds as sources of cell carbon and energy. In this work, we studied the initial steps in the aromatic metabolism of this strictly anaerobic model organism. An ATP-dependent benzoate coenzyme A (CoA) ligase (AMP plus PPi forming) composed of a single 59-kDa subunit was purified from extracts of cells grown on benzoate. Specific activity was highest with benzoate and some benzoate derivatives, whereas aliphatic carboxylic acids were virtually unconverted. The N-terminal amino acid sequence showed high similarities with benzoate CoA ligases from Thauera aromatica and Azoarcus evansii. When cultivated on benzoate, cells strictly required selenium and molybdenum, whereas growth on nonaromatic compounds, such as cyclohexanecarboxylate or lactate, did not depend on the presence of the two trace elements. The growth rate on benzoate was half maximal with 1 nM selenite present in the growth medium. In molybdenum- and/or selenium-depleted cultures, growth on benzoate could be induced by addition of the missing trace elements. In extracts of cells grown on benzoate in the presence of [75Se]selenite, three radioactively labeled proteins with molecular masses of approximately 100, 30, and 27 kDa were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The 100- and 30-kDa selenoproteins were 5- to 10-fold induced in cells grown on benzoate compared to cells grown on lactate. These results suggest that the dearomatization process in D. multivorans is not catalyzed by the ATP-dependent Fe-S enzyme benzoyl-CoA reductase as in facultative anaerobes but rather involves unknown molybdenum- and selenocysteine-containing proteins.
Amino Acid Sequence↗
Benzoate stimulates glutamate release from perfused rat liver.
In isolated perfused rat liver, benzoate addition to the influent perfusate led to a dose-dependent, rapid and reversible stimulation of glutamate output from the liver. This was accompanied by a decrease in glutamate and 2-oxoglutarate tissue levels and a net K+ release from the liver; withdrawal of benzoate was followed by re-uptake of K+. Benzoate-induced glutamate efflux from the liver was not dependent on the concentration (0-1 mM) of ammonia (NH3 + NH4+) in the influent perfusate, but was significantly increased after inhibition of glutamine synthetase by methionine sulphoximine or during the metabolism of added glutamine (5 mM). Maximal rates of benzoate-stimulated glutamate efflux were 0.8-0.9 mumol/min per g, and the effect of benzoate was half-maximal (K0.5) at 0.8 mM. Similar Vmax. values of glutamate efflux were obtained with 4-methyl-2-oxopentanoate, ketomethionine (4-methylthio-2-oxobutyrate) and phenylpyruvate; their respective K0.5 values were 1.2 mM, 3.0 mM and 3.8 mM. Benzoate decreased hepatic net ammonia uptake and synthesis of both urea and glutamine from added NH4Cl. Accordingly, the benzoate-induced shift of detoxication from urea and glutamine synthesis to glutamate formation and release was accompanied by a decreased hepatic ammonia uptake. The data show that benzoate exerts profound effects on hepatic glutamate and ammonia metabolism, providing a new insight into benzoate action in the treatment of hyperammonaemic syndromes.
Ammonium Chloride↗
Flux limitations in the ortho pathway of benzoate degradation of Alcaligenes eutrophus: metabolite overflow and induction of the meta pathway at high substrate concentrations.
The growth behaviour of Alcaligenes eutrophus using various concentrations of benzoate was investigated. In batch culture, growth was exponential and growth rate (mu) and yields (Y) were high [mu = 0.51 h-1 and Yx/benzoate = 0.56 mol carbon (mol carbon)-1] when low concentrations of benzoate (< 5 mM) were used. These kinetic parameters were close to the maxima determined in a benzoate-limited chemostat [mu(max) = 0.55 h-1 and YX/benzoatemax = 0.57 mol carbon (mol carbon)-1] and the part of the energy for maintenance was limited (mATP = 4.3 +/- 2.2 mmol ATP g-1 h-1). When higher concentrations of benzoate were used (up to 40 mM), several metabolic limitations appeared. The specific rate of benzoate consumption was not altered, whereas growth was inhibited [Ki(benzoate) approximately 27 mM]. Furthermore, high concentrations of catechol together with some 1,2-dihydro-1,2-dihydroxybenzoate (DHB) transiently accumulated in the medium. The accumulation of catechol was attributed to limiting flux through catechol 1,2-dioxygenase estimated to be 5.2 mmol g-1 h-1, whereas that of DHB was provoked by an imbalance in the NADH/NAD+ intracellular content. The direct consequence of DHB accumulation was the induction of the meta pathway for the degradation of catechol, and this pathway contributed up to 20% of the total flux of catechol to the central metabolism. Finally, when very high concentrations of benzoate were used (55 mM), both growth and the specific rate of benzoate degradation were diminished due to a strong decrease in benzoate 1,2-dioxygenase specific activity.
Adenosine Triphosphate↗
Effect of sodium benzoate on blood ammonia response to oral glutamine challenge in cirrhotic patients: a note of caution.
OBJECTIVE: The administration of sodium benzoate provides an alternative pathway for the disposal of waste nitrogen and this substance has been used to treat patients with urea cycle defects and more recently cirrhotics with hepatic encephalopathy. The aim of the study was to assess the ammonia-lowering effect of benzoate in cirrhotic patients without overt hepatic encephalopathy. METHODS: Glutamine challenge, a method to induce an increase of blood ammonia, was performed in six cirrhotics before and after 5 days of benzoate treatment (10 microg/day). Number Connection Test and Posner's Attention Test were also performed before and after benzoate treatment. RESULTS: Blood ammonia increased after the glutamine load both before (from 66 +/- 12 microg/dl to 123 +/- 34 microg/dl and 179 +/- 53 microg/dl after 30 and 60 min, respectively; ANOVA p = 0.0004) and after benzoate treatment (from 102 +/- 27 microg/dl to 185 +/- 49 microg/dl and 250 +/- 39 microg/dl after 30 and 60 min, respectively; ANOVA p = 0.00001). However, after benzoate treatment, the basal values (102 +/- 27 vs 66 +/- 12 microg/dl; p = 0.01) and peak increments of ammonia (166 +/- 56 microg/dl vs 102 +/- 40 microg/dl; p = 0.04) were significantly higher than before. The Number Connection test and the Posner's test were not altered by benzoate treatment. CONCLUSIONS: Benzoate increased both the basal and post-glutamine ammonia levels. These results confirm what has already been observed in experimental animals and suggest a note of caution in the use of sodium benzoate in cirrhotic patients.
Administration, Oral↗
Metabolism of benzoate, cyclohex-1-ene carboxylate, and cyclohexane carboxylate by "Syntrophus aciditrophicus" strain SB in syntrophic association with H(2)-using microorganisms.
The metabolism of benzoate, cyclohex-1-ene carboxylate, and cyclohexane carboxylate by "Syntrophus aciditrophicus" in cocultures with hydrogen-using microorganisms was studied. Cyclohexane carboxylate, cyclohex-1-ene carboxylate, pimelate, and glutarate (or their coenzyme A [CoA] derivatives) transiently accumulated during growth with benzoate. Identification was based on comparison of retention times and mass spectra of trimethylsilyl derivatives to the retention times and mass spectra of authentic chemical standards. (13)C nuclear magnetic resonance spectroscopy confirmed that cyclohexane carboxylate and cyclohex-1-ene carboxylate were produced from [ring-(13)C(6)]benzoate. None of the metabolites mentioned above was detected in non-substrate-amended or heat-killed controls. Cyclohexane carboxylic acid accumulated to a concentration of 260 microM, accounting for about 18% of the initial benzoate added. This compound was not detected in culture extracts of Rhodopseudomonas palustris grown phototrophically or Thauera aromatica grown under nitrate-reducing conditions. Cocultures of "S. aciditrophicus" and Methanospirillum hungatei readily metabolized cyclohexane carboxylate and cyclohex-1-ene carboxylate at a rate slightly faster than the rate of benzoate metabolism. In addition to cyclohexane carboxylate, pimelate, and glutarate, 2-hydroxycyclohexane carboxylate was detected in trace amounts in cocultures grown with cyclohex-1-ene carboxylate. Cyclohex-1-ene carboxylate, pimelate, and glutarate were detected in cocultures grown with cyclohexane carboxylate at levels similar to those found in benzoate-grown cocultures. Cell extracts of "S. aciditrophicus" grown in a coculture with Desulfovibrio sp. strain G11 with benzoate or in a pure culture with crotonate contained the following enzyme activities: an ATP-dependent benzoyl-CoA ligase, cyclohex-1-ene carboxyl-CoA hydratase, and 2-hydroxycyclohexane carboxyl-CoA dehydrogenase, as well as pimelyl-CoA dehydrogenase, glutaryl-CoA dehydrogenase, and the enzymes required for conversion of crotonyl-CoA to acetate. 2-Ketocyclohexane carboxyl-CoA hydrolase activity was detected in cell extracts of "S. aciditrophicus"-Desulfovibrio sp. strain G11 benzoate-grown cocultures but not in crotonate-grown pure cultures of "S. aciditrophicus". These results are consistent with the hypothesis that ring reduction during syntrophic benzoate metabolism involves a four- or six-electron reduction step and that once cyclohex-1-ene carboxyl-CoA is made, it is metabolized in a manner similar to that in R. palustris.
Benzoates↗
Uptake of benzoate by Rhodopseudomonas palustris grown anaerobically in light.
The uptake and anaerobic metabolism of benzoate were studied in short-term experiments with phototrophic cells of Rhodopseudomonas palustris. Cells that were preincubated and assayed anaerobically in the presence of 1 mM dithiothreitol accumulated [7-14C]benzoate at a rate of at least 0.5 nmol . min-1 . mg-1 of protein. Cells that were preincubated aerobically, or anaerobically in the absence of a reducing agent or an electron donor such as succinate, took up benzoate at reduced rates. Benzoate was removed from the external medium with remarkably high efficiency; initial uptake rates were independent of substrate concentration, and uptake remained linear down to concentrations of less than 1 microM. Uptake rates were not sensitive to external pH in the range of 6.5 to 8.1, and very little free benzoate was found associated with the cells. By contrast, benzoyl coenzyme A (CoA) was formed rapidly in cells exposed to labeled benzoate. Its appearance in such cells, together with the more gradual accumulation of other compounds tentatively identified as reduction products, is consistent with the identification of benzoyl CoA as an intermediate in the anaerobic reductive metabolism of benzoate. The very effective uptake of external benzoate can be explained by its conversion to benzoyl CoA immediately after its passage across the cell membrane by simple or facilitated diffusion. Such a chemical conversion would serve to maintain a downhill concentration gradient between the cell cytoplasm and the cell surroundings, even at very low external benzoate concentrations.
Acyl Coenzyme A↗