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At least 343 records · Page 19Linked to original sources
PubMed1987

The elucidation of the microheterogeneity of highly purified p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens by various biochemical techniques.

Highly purified p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens can be separated into at least five fractions by anion-exchange chromatography. All fractions exhibit the same specific activity and the enzyme exists mainly in the dimeric form in solution. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of a mixture of the different fractions reveals two apparent forms of enzyme molecules, while isoelectric focusing experiments, on the other hand, reveal six apparently different forms of enzyme molecules. It is shown that the different forms of enzyme molecules are due to the (partial) oxidation of Cys-116 in the sequence of the enzyme. This interpretation of the data is supported by kinetic measurements of the formation of hybrid dimeric molecules monitored by fast protein liquid chromatography, using purified enzyme containing Cys-116 either in the native and or the fully oxidized (sulfonic acid) state. By chemical modification studies using maleimide derivatives, 5,5'-dithiobis(2-nitrobenzoate) and H2O2, it is shown that sulfenic, sulfinic and sulfonic acid derivatives of Cys-116 are products of oxidation. The results are briefly discussed with respect to the possibility that this isolation artifact might also be partially responsible for the appearance of multiple forms of enzyme molecules in other biochemical preparations.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1988

Chemical modification of tyrosine-38 in p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens by 5'-p-fluorosulfonylbenzoyladenosine: a probe for the elucidation of the NADPH binding site? Involvement in catalysis, assignment in sequence and fitting to the tertiary structure.

p-Hydroxybenzoate hydroxylase from Pseudomonas fluorescens was covalently modified by the nucleotide analog 5'-(p-fluorosulfonylbenzoyl)-adenosine in the presence of 20% dimethylsulfoxide. The inactivation reaction is pH-dependent and does not obey pseudo-first-order kinetics, due to spontaneous hydrolysis of the reagent. The kinetic data further indicate that a weak, reversible enzyme-inhibitor complex is an intermediate in the inactivation reaction and that only one amino acid residue is responsible for the loss of activity. The inactivation is strongly inhibited by NADPH and 2',5'ADP. Steady-state kinetics and 2',5'ADP bioaffinity chromatography of the modified enzyme suggest that the essential residue is not directly involved in NADPH binding. Sequence studies show that Tyr-38 is the main residue protected from modification in the presence of NADPH. From crystallographic studies it is known that the hydroxyl group of Tyr-38 is 1.84 nm away from the active site. Model-building studies using computer graphics show that this distance can be accommodated when FSO2BzAdo binds in an extended conformation with the sulfonylbenzoyl portion in an orientation different from the nicotin-amide ring of NADPH.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1987

The influence of viscosity on the migration of chloramphenicol and 4-hydroxybenzoic acid through glycerogelatin gels.

Migration of chloramphenicol and 4-hydroxybenzoic acid from solutions in 1-octanol into Glycerol Suppository Base, BP and soft gelatin capsule shells is reported. Rates of migration through the gels, quantified in terms of diffusion coefficients, are given. An electron spin resonance probing technique was used to determine the microscopic viscosity. The latter, rather than the bulk viscosity, was shown to be the major rheological influence on the rate of diffusion.

Chloramphenicol↗
PubMed1987

On the mechanism of transport of salicylate and p-hydroxybenzoic acid across human red cell membranes.

The pH-dependence of efflux of salicylate and p-hydroxybenzoic acid (PHB) from human red cells indicates that the un-ionized species penetrates the membrane. No effect of the anion channel blocker 4,4'-diisothiocyano-2,2'-disulphonic stilbene was observed. The temperature-dependence of efflux suggests that the energy barrier to transport of salicylate and PHB is the transfer of the acids from water into the membrane, rather than transport through the membrane interior. Intracellular binding of both acids was found to be pH-dependent.

Biological Transport↗
PubMed1979

Inhibition of Clostridium botulinum by p-hydroxybenzoic acid n-alkyl esters.

Twelve straight-chain esters, C(5) to C(14), C(16), and C(18), of p-hydroxybenzoic acid were prepared, and their melting points, solubilities in water at 25 degrees C, infrared spectra, dissociation constants (pK(a)), and activities against Clostridium botulinum were determined. These studies also included four commercial straight-chain esters, C(1) to C(4). The most potent activity was exhibited by undecyl and dodecyl esters, which are about 300 times as active as sodium nitrite. Quadratic and cubic equations were developed correlating the activity with pK(a) values and chain length of the esters, respectively.

Chemical Phenomena↗
PubMed1996

Characterization of Desulfitobacterium chlororespirans sp. nov., which grows by coupling the oxidation of lactate to the reductive dechlorination of 3-chloro-4-hydroxybenzoate.

Strain Co23, an anaerobic spore-forming microorganism, was enriched and isolated from a compost soil on the basis of its ability to grow with 2,3-dichlorophenol (DCP) as its electron acceptor, ortho chlorines were removed from polysubstituted phenols but not from monohalophenols. Growth by chlororespiration was indicated by a growth yield of 3.24 g of cells per mol of reducing equivalents (as 2[H]) from lactate oxidation to acetate in the presence of 3-chloro-4-hydroxybenzoate but no growth in the absence of the halogenated electron acceptor. Other indicators of chlororespiration were the fraction of electrons from the electron donor used for dechlorination (0.67) and the H2 threshold concentration of < 1.0 ppm. Additional electron donors utilized for reductive dehalogenation were pyruvate, formate, butyrate, crotonate, and H2. Pyruvate supported homoacetogenic growth in the absence of an electron acceptor. Strain Co23 also used sulfite, thiosulfate, and sulfur as electron acceptors for growth, but it did not use sulfate, nitrate or fumarate. The temperature optimum for growth was 37 degrees C; however, the rates of dechlorination were optimum at 45 degrees C and activity persisted to temperatures as high as 55 degrees C. The 16S rRNA sequence was determined, and strain Co23 was found to be related to Desulfitobacterium dehalogenans JW/IU DC1 and Desulfitobacterium strain PCE1, with sequence similarities of 97.2 and 96.8%, respectively. The phylogenetic and physiological properties exhibited by strain Co23 place it into a new species designated Desulfitobacterium chlororespirans.

Anaerobiosis↗
PubMed2002

Aerobic metabolism of 4-hydroxybenzoic acid in Archaea via an unusual pathway involving an intramolecular migration (NIH shift).

A novel haloarchaeal strain, Haloarcula sp. strain D1, grew aerobically on 4-hydroxybenzoic acid (4HBA) as a sole carbon and energy source and is the first member of the domain Archaea reported to do so. Unusually, D1 metabolized 4HBA via gentisic acid rather than via protocatechuic acid, hydroquinone, or catechol. Gentisate was detected in 4HBA-grown cultures, and gentisate 1,2-dioxygenase activity was induced in 4HBA-grown cells. Stoichiometric accumulation of gentisate from 4HBA was demonstrated in 4HBA-grown cell suspensions containing 2,2'-dipyridyl (which strongly inhibits gentisate 1,2-dioxygenase). To establish whether initial 1-hydroxylation of 4HBA with concomitant 1,2-carboxyl group migration to yield gentisate occurred, 2,6-dideutero-4HBA was synthesized and used as a substrate. Deuterated gentisate was recovered from cell suspensions and identified as 3-deutero-gentisate, using gas chromatography-mass spectrometry and proton nuclear magnetic resonance spectroscopy. This structural isomer would be expected only if a 1,2-carboxyl group migration had taken place, and it provides compelling evidence that the 4HBA pathway in Haloarcula sp. strain D1 involves a hydroxylation-induced intramolecular migration. To our knowledge, this is the first report of a pathway which involves such a transformation (called an NIH shift) in the domain Archaea.

2,2'-Dipyridyl↗
PubMed1984

Determination of HDL-cholesterol using 2,4,6-tribromo-3-hydroxybenzoic acid with a commercial CHOD-PAP reagent.

The Boehringer one-component high-performance cholesterol oxidase reagent has been modified by the inclusion of 2,4,6-tribromo-3-hydroxybenzoic acid (TBHBA) to give a fourfold increase in sensitivity to a molar absorbance of approximately equal to 29,000 with respect to cholesterol. The resulting reagent system is particularly suitable for the determination of plasma HDL-cholesterol for which a reagent of high sensitivity is required. A simple method of bromination avoiding the use of elemental bromine is used to prepare TBHBA. The modified reagent system has been found to have good within- and between-batch precision and has shown itself to be reliable and trouble-free.

Bromobenzoates↗
PubMedDate not supplied

Dimethacrylates derived from hydroxybenzoic acids.

Since the color stabilities and durabilities of current composite and pit and fissure sealant resins need improvement, it is worthwhile to evaluate innovations that might accomplish this goal. Accordingly, three crystalline dimethacrylate monomers with low melting points were prepared from the isomeric hydroxybenzoic acids and 2-bromo-ethyl methacrylate. These monomers can be purified by crystallization and liquified by admixture in various proportions to obtain a polymerizable liquid of suitable viscosity at room temperature. In contrast to the analogous dimethacrylate monomers that were derived from the phthalic acid isomers, these aromatic ether-ester dimethacrylates do not form colored charge-transfer complexes with tertiary aromatic amine accelerators. These monomers and their polymers should be elevated for use in composites and pit and fissure sealant formulations.

Acrylates↗
PubMed1998

Synthesis and anti-human immunodeficiency virus type 1 integrase activity of hydroxybenzoic and hydroxycinnamic acid flavon-3-yl esters.

A series of new hydroxybenzoic and hydroxycinnamic acid flavon-3-yl esters were synthesized in order to obtain compounds targeting the human immunodeficiency virus (HIV) type 1 integrase (IN). The esters were tested for anti-IN and anti-reverse transcriptase (RT) activity in enzyme assays and for anti-HIV-1, anti-proliferative and anti-topoisomerase activity in cell-based assays. In enzyme assays, the two gallic acid flavon-3-yl esters showed a notable IN inhibition (IC50 values were 8.3 and 9.1 microM, respectively), while the two caffeic acid flavon-3-yl esters exhibited a modest activity (IC50 75 and 60 microM, respectively). Replacement of hydroxyl groups resulted in loss of potency. Caffeic acid 3',4'-dichloroflavon-3-yl ester also inhibited the RT activity whereas it was not active on human topoisomerases. It therefore represents an interesting example of a compound specifically targeting more than one step of the virus replication cycle.

Anti-HIV Agents↗
PubMedDate not supplied

Oxidative decarboxylation of para-hydroxybenzoic acids by peroxidases under in vivo and in vitro conditions.

Oxidative decarbyxylation of p-hydroxybenzoic acids in plant cell suspension cultures is catalyzed by peroxidases. This reaction has been characterized in vivo and in vitro. Decarboxylation of substituted benzoic acids yields monomeric, dimeric and oligomeric benzoquinones. All peroxidases obtained from soybean (Glycine max) cell suspension cultures by gel electrophoresis are equally capable to decarboxylate p-hydroxygenzoic acids as indicated by their rather low differences in specific activity for various benzoic acids.

Decarboxylation↗
PubMed1981

A genetic approach to the biosynthesis of the rifamycin-chromophore in Nocardia mediterranei. IV. Identification of 3-amino-5-hydroxybenzoic acid as a direct precursor of the seven-carbon amino starter-unit.

3-Amino-5-hydroxybenzoic acid was investigated for its ability to induce rifamycin biosynthesis in an appropriate mutant of Nocardia mediterranei and identified as a direct precursor of the seven-carbon amino starter-unit for the biosynthesis of ansamycins. A model for the biosynthesis of different types of ansamycins is presented and discussed.

Aminobenzoates↗
PubMed1983

3-Amino-5-hydroxybenzoic acid in antibiotic biosynthesis. VI. Directed biosynthesis studies with ansamycin antibiotics.

Biosynthesis of the ansamycin antibiotic actamycin (2) was markedly increased by the addition of the precursor 3-amino-5-hydroxybenzoic acid (1) to the producing Streptomyces fermentation. Similar addition of the 4-chloro, 6-chloro, N-methyl and O-methyl analogues 4, 6, 5 and 7 of the amino acid 1 reduced actamycin production and did not yield structurally modified ansamycins. These results with the analogues 4, 5 and 7 indicate that the corresponding chlorine, N-methyl and O-methyl substituents present in the nuclei of various ansamycins are introduced at biosynthetic stages beyond the level of the amino acid 1.

Aminobenzoates↗
PubMed1991

Biosynthesis of the streptovaricins: 3-amino-5-hydroxybenzoic acid as a precursor to the meta-C7N unit.

[Carboxy-14C]-3-amino-5-hydroxybenzoic acid (AHBA) has been shown to be incorporated by Streptomyces spectabilis to the extent of greater than 0.1% (35: 1 dilution) in the ansamycin antibiotic streptovaricin C, the major component of the streptovaricin complex. When [carboxy-13C]AHBA was similarly administered, C-21 (quinone methide carbonyl at 188.3 ppm) of streptovaricin C was specifically labeled (at twenty one times natural abundance). In preparation for the 13C incorporation study the 13C NMR spectrum of streptovaricin C was investigated, making extensive use of short- and long-range HETCOR. These assignments revise some of those proposed earlier for streptovaricin C.

Aminobenzoates↗
PubMed1991

Interpretation of the spectra observed during oxidation of p-hydroxybenzoate hydroxylase reconstituted with modified flavins.

Oxidation of reduced p-hydroxybenzoate hydroxylase by oxygen in the presence of 2,4-dihydroxybenzoate and azide proceeds via three well established intermediates. Reconstitution of the apoprotein with either 8-thiophenyl-FAD, 8-fluoro-FAD, 8-chloro-FAD, or 8-sulfonyl-FAD does not alter this sequence of events. However, the peak positions of the intermediate spectra are somewhat shifted relative to those of native enzyme. Comparison of the spectra for intermediates II and III leads to the conclusion that the spectrum for intermediate II is a composite. One component is the spectrum of an intermediate III-like species, and the other appears to be related to the substrate. The substrate component is pH-dependent, having an absorbance maximum of 386 nm (extinction, approximately 6,000 M-1 cm-1) at pH 6.6 which shifts to approximately 430 nm (extinction, approximately 11-13,000 M-1 cm-1) at pH 9.2, with a pK of 7.9. The pH dependence for the spectrum of the substrate component combined with the pH independence of the intermediate III-like spectrum satisfactorily accounts for the pH dependence observed for intermediate II, including the fact that the high pH spectrum of native intermediate II is qualitatively quite different from that of 8-sulfonyl-FAD intermediate II.

4-Hydroxybenzoate-3-Monooxygenase↗
PubMed1976

P-Hydroxybenzoic acid hydrazide procedure for serum glucose adapted to the Technicon "SMA 12/60," and compared with other glucose methods.

We adapted the p-hydroxybenzoic acid hydrazide procedure for serum glucose for use with the Technicon SMA 12/60 AutoAnalyzer. Like the o-toluidine method, this method is based on a general carbohydrate reaction except that it occurs in a mildly alkaline medium and the intense yellow color formed is measured at 400 nm. Advantages of this reagent over o-toluidine include lower cost, less toxicity, and higher purity. Aside from those carbohydrates that are present in serum in insignificant quantities, there are no interferences from various physiological compounds or drugs (hypoglycemic agents) found either in normal persons or diabetics. Within-run and day-to-day values had coefficients of variation of 1.39% and 3.44%, respectively; recoveries ranged from 100 to 102% (mean, 101%). Comparative data showed excellent agreement with the hexokinase (r equals 0.998; y equals 0.950x + 5.91) and glucose oxidase (r equals 0.996; y equals 0.986x + 5.34) enzymatic ("true") glucose methods, and with the o-toluidine procedure (r equals 0.998; y equals 0.979x + 3.14).

Autoanalysis↗
PubMed1988

Enzymic determination of the free cholesterol fraction of high-density lipoprotein in plasma with use of 2,4,6-tribromo-3-hydroxybenzoic acid.

A highly sensitive enzymic colorimetric reagent is described for determination of the free cholesterol fraction of high-density lipoprotein (HDL), which represents about 20% of the total cholesterol content of this lipoprotein. For greater sensitivity with respect to cholesterol, I used 2,4,6-tribromo-3-hydroxybenzoic acid instead of phenol in the cholesterol oxidase/peroxidase/4-aminoantipyrine reagent system. This allows determination of the free cholesterol fraction of HDL isolates prepared with polyethylene glycol 6000, a method for precipitating beta-lipoprotein that involves a twofold dilution of plasma. The reagent, adapted for use with a Cobas-Bio centrifugal analyzer, results in between-run and within-run CVs of less than 3% and a linearity to at least 400 mg of HDL free cholesterol per liter. Comparison with results by Trinder's cholesterol method, which measures cholest-4-en-3-one at 232 nm, showed good correlation (r = 0.9829, slope 1.0001, and y-intercept +2.4797 mg/L). With the manual procedure for HDL free cholesterol, between-batch and within-batch CVs were less than 5%, and results correlated well with those by the automated method (r = 0.9975, slope 0.9839, and y-intercept +2.4327 mg/L). The mean (and SD) HDL free cholesterol for 123 men was 96.8 (30.6) mg/L and for 122 women 136.4 (36.8) mg/L, indicating a distinct sex-related difference, similar to that found for HDL total cholesterol. HDL free cholesterol in plasma may therefore be a potential new predictor of coronary heart disease.

Adult↗
PubMed1977

Controlled evaluation of the antitussive activity of viminol p-hydroxybenzoate.

A double-blind cross-over trial was carried out to evaluate the antitussive activity of viminol p-hydroxybenzoate; the comparison was done with three preparations: a placebo and the drug at two doses, 70 and 140 mg respectively. The responses were scored hourly up to 4 hours after the administration of single doses in the morning to subjects with persistent cough. The highest dose of viminol showed a definite antitussive activity, whereas the lowest did not differ from the placebo. The antitussive effect appears clinically useful for the treatment of cough, but further studies are indicated to define optimal dosage schedules.

Clinical Trials as Topic↗