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PubMed2000

4-Hydroxybenzoate uptake in an isolated soil Acinetobacter sp.

The isolated soil bacteria Acinetobacter strain BEM2 is able to utilize some xenobiotic aromatic compounds as a carbon source. In this study the metabolism of 4-hydroxybenzoate (4-HBA) by strain BEM2 was characterized. Degradation involved a meta-cleavage pathway yielding 3,4-dihydroxybenzoate (3,4-DHBA) as an intermediate and CO(2) as the principal product from the C atoms in the aromatic ring. 4-HBA uptake was studied, and the kinetic parameters were determined. The uptake was shown to be directly coupled to ATP hydrolysis and its synthesis, according to the Mitchell chemiosmotic hypothesis.

Acinetobacter↗
PubMed2006

Influence of crystal structure on the compaction properties of n-alkyl 4-hydroxybenzoate esters (parabens).

PURPOSE: The aim of the study is to examine the influence of slip planes on the nanoindentation hardness and compaction properties of methyl, ethyl, n-propyl, and n-butyl 4-hydroxybenzoate (parabens). METHODS: Molecular modeling calculations, embodying the attachment energy concept, were performed to predict the slip planes in the crystal lattices, whereas the nanoindentation hardness of the crystals and the tensile strength of directly compressed compacts were measured. RESULTS: Unlike the other three parabens, methyl paraben has no slip planes in its crystal lattice, and its crystals showed greater nanoindentation hardness, corresponding to lower plasticity, whereas its tablets exhibited substantially lower tensile strength than those of ethyl, propyl, or butyl paraben. CONCLUSIONS: The nanoindentation hardness of the crystals and the tensile strength of directly compressed tablets were each found to correlate directly with the absence or presence of slip planes in the crystal structures of the parabens because slip planes confer greater plasticity. This work presents a molecular insight into the influence of crystal structural features on the tableting performance of molecular crystals in general and of crystalline pharmaceuticals in particular.

Crystallization↗
PubMed2004

The AtPPT1 gene encoding 4-hydroxybenzoate polyprenyl diphosphate transferase in ubiquinone biosynthesis is required for embryo development in Arabidopsis thaliana.

4-Hydroxybenzoate polyprenyl diphosphate transferase (4HPT) is the key enzyme that transfers the prenyl side chain to the benzoquione frame in ubiquinone (UQ) biosynthesis. The Arabidopsis AtPPT1 cDNA encoding 4HPT was cloned by reverse transcription-polymerase chain reaction (RT-PCR) based on the information of the Arabidopsis genomic sequence, and the function of the gene was determined. Heterologous expression of the AtPPT1 gene enabled restoration of the respiratory ability and UQ synthesis in a yeast mutant that was defective in 4HPT activity. The mitochondrial fraction that was prepared from the yeast mutant, which expressed the AtPPT1 gene, exhibited 4HPT enzymatic activity with geranyl diphosphate (GPP) as the prenyl substrate. This indicated that the AtPPT1 gene encodes active 4HPT with a broad substrate specificity in terms of the prenyl donor. The AtPPT1 mRNA was predominantly expressed in the flower cluster, and the green fluorescent protein (GFP) fused with the signal peptide of AtPPT1 was translocated into the mitochondria. T-DNA insertion mutation that disrupts the AtPPT1 gene in Arabidopsis resulted in the arrest of embryo development at an early stage of zygotic embryogenesis. These results demonstrate that the AtPPT1 gene involved in the biosynthesis of mitochondrial UQ plays an essential role in embryo development in Arabidopsis .

Alkyl and Aryl Transferases↗
PubMed1976

Membrane-associated reactions in ubiquinone biosynthesis in Escherichia coli. 3-Octaprenyl-4-hydroxybenzoate carboxy-lyase.

A sensitive and quantitative assay for 3-octaprenyl-4-hydroxybenzoate carboxy-lyase has been developed. This enzyme, which catalyses the third reaction in ubiquinone biosynthesis in Escherichia coli, was partially purified and some of its properties determined. It was found that a considerable proportion of the carboxylyase activity could be separated from the membrane fraction in cell extracts prepared using a French press. Gel filtration showed the molecular weight of the enzyme to be about 340 000. For optimal activity the carboxy-lase was shown to require Mn2+, washed membranes or an extract of phospholipids, and an unidentified heat stable factor of molecular weight less than 10 000. The carboxy-lyase reaction was also shown to be strongly stimulated by dithiothreitol and methanol. The properties of the carboxy-lyase are compared with the three other enzymes concerned with ubiquinone biosynthesis in E. coli which have been studied in vitro. The fact that the substrate of the carboxy-lyase is membrane-bound and the enzyme is stimulated by phospholipid suggests that it normally functions in association with the cytoplasmic membrane in vivo.

Bacterial Proteins↗
PubMed1984

Ortho-hydroxybenzoates may act at the protein fraction to enhance membrane permeability.

Experimental observation suggests that the ability of ortho-hydroxybenzoates to alter the permeability of rat rectal epithelial membrane may involve an interaction between the ortho-isomer and the membrane protein. Such an interaction may cause a temporary structural modification of the protein rendering the membrane permeable to compounds normally poorly absorbed from the rectal compartment.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

Characterization of polyprenyldiphosphate: 4-hydroxybenzoate polyprenyltransferase from Escherichia coli.

Polyprenyldiphosphate: 4-hydroxybenzoate polyprenyltransferase (4-HB polyprenyltransferase) is a key enzyme in ubiquinone biosynthesis in E. coli, encoded by the gene ubiA. By overexpression of ubiA and isolation of the membrane fraction, the enzyme was enriched approx. 3000-fold and characterized. The enzyme is membrane-bound and could not be solubilized by hypotonic buffer or detergent treatment. The enzymatic activity is optimal at pH 7.8 and depends on the presence of magnesium ions. Geranyldiphosphate (GPP), all-trans-farnesyldiphosphate (FPP) and all-trans-solanesyldiphosphate (SPP) are accepted as side chain precursors. The apparent Km values for these substances are are 254 microM, 22 microM and 31 microM, respectively. No reaction was observed with omega-t2-c5-octaprenyldiphosphate, in which five double bounds have cis-configuration. The reaction is stimulated by 0.01% CHAPS, but strongly inhibited by sodiumdeoxycholate, Tween 80 and Triton X-100. The amino acid sequence shows striking similarities to 4-HB hexaprenyltransferase from yeast. Sequence homologies to other prenyltransferases are discussed.

Alkyl and Aryl Transferases↗
PubMed1986

Sequence-specific modification of DNA by 6-hydroxybenzo[a]pyrene.

6-Hydroxybenzo[a]pyrene cleaved phi X174 supercoiled DNA to open circular DNA in the presence of heavy metal ions. It induced an alkali-labile modification in DNA via an oxygen-radical-mediated reaction; the most frequent alkali-labile sites were on the 3' side of the pyrimidine residues of the pyrimidine cluster.

Bacteriophage phi X 174↗
PubMed1991

para-hydroxybenzoate as an intermediate in the anaerobic transformation of phenol to benzoate.

Anaerobic phenol transformation was studied using a consortium which transformed phenol to benzoate without complete mineralization of benzoate. Products of monofluorophenol transformation indicated para-carboxylation. Phenol and benzoate were detected during para-hydroxybenzoate (p-OHB) degradation. p-OHB was detected in phenol-transforming cultures containing 6-hydroxynicotinic acid (6-OHNA), a structural analogue of p-OHB, or at elevated initial concentrations of phenol (greater than or equal to 5 mM), or benzoate (greater than or equal to 10 mM).

Anaerobiosis↗
PubMed1980

Genetic differences between C57BL/6 and DBA/2 mice in the inductions of UDP-glucuronyl transferases for 3-hydroxybenzo(a)pyrene, p-nitrophenol, and bilirubin by 3-methylcholanthrene.

In C57BL/6 mice, aryl hydrocarbon hydroxylase (AHH) increased 1 day after treatment with 3-methylcholanthrene, and induction of UDP-glucuronyl transferases for 3-hydroxybenzo(a)pyrene, p-nitrophenol and bilirubin in the liver microsomes was observed 2 to 5 days later. In DBA/2 mice, neither AHH nor transferase activities were influenced by 3-methylcholanthrene. These results suggest that induction of activating and detoxicating enzymes is genetically linked.

Animals↗
PubMed2005

Uterotrophic effects of benzophenone derivatives and a p-hydroxybenzoate used in ultraviolet screens.

Ultraviolet (UV) sunscreen products are popular because of concerns about UV radiation and skin cancer. Unfortunately, some of these products contain agents with estrogenic activity. We used an ovariectomized rat uterotrophic assay to measure the estrogenic activities of 2,4-dihydroxybenzophenone (2,4-DHBP), 2,2',4,4'-tetrahydroxybenzophenone (2,2',4,4'-THBP), and 4-hydroxybenzoic acid isobutyl ester (isobutyl-paraben), which are agents in UV sunscreens, and ethynyl estradiol (EE) and bisphenol A (BPA), which are positive controls. All chemicals increased rat uterine weights. The 10% effective doses (ED10, mg/kg/day) of EE, BPA, 2,4-DHBP, 2,2',4,4'-THBP, and isobutyl-paraben, as determined by Hill equation analysis, where 5E-5, 41.1, 544.6, 33.0, and 230.9, respectively, and their relative potencies against EE were about 1/800,000, 1/10,000,000, 1/600,000, and 1/4,000,000, respectively. Our findings indicated that UV screens contain weak estrogenic compounds.

Animals↗
PubMed2004

Lack of spermatotoxic effects of methyl and ethyl esters of p-hydroxybenzoic acid in rats.

Parabens are alkyl esters of p-hydroxybenzoic acid widely used as preservatives in foodstuffs, cosmetics toiletries and pharmaceuticals. These compounds are known to exert a weak estrogenic activity in estrogen receptor assays in vitro. In addition butyl and propyl parabens show uterotrophic activity in vivo. It was previously shown that exposure of post-weaning rats and mice to butyl or propyl parabens adversely affects the secretion of testosterone and the function of the male reproductive system. In the present study, it is shown that methyl and ethyl parabens do not adversely affect the secretion of sex hormones or the male reproductive function. Methyl and ethyl parabens were administered to 25-27-day-old rats assigned to five groups of eight animals each, at doses of 0.1% and 1.0% each in the rat's diet. At the end of 8 weeks, the rats were sacrificed by decapitation and the weights of the testes, epididymides, prostates, seminal vesicles and preputial glands were determined. There were no treatment-related effects of either compound on the organ weights in any of the study groups. Neither compound exhibited anti-spermatogenic effects nor elicited changes in levels of testosterone, LH and FSH at a dose level of about 1000 mg/kg of body weight per day.

Animals↗
PubMed2006

Fast simultaneous determination of urinary 1-hydroxypyrene and 3-hydroxybenzo[a]pyrene by liquid chromatography-tandem mass spectrometry.

A fast analysis method using liquid chromatography-atmospheric pressure chemical ionization tandem mass spectrometry was developed for the simultaneous determination of the 1-hydroxypyrene (1-OHP) and 3-hydroxybenzo[a]pyrene (3-OHBaP) in urine. Mass transitions were monitored at m/z 219.3-200.0 for 1-OHP and m/z 269.2-252.2 for 3-OHBaP. Only 10 min was needed for the analysis. The recovery was 60% for 3-OHBaP and 91% for 1-OHP, respectively. And the method detection limits were 0.49 microg/L for 1-OHP and 1.03 microg/L for 3-OHBaP. The inter- and intra-day relative standard deviations were in the range of 2.8-8.9% for 1-OHP and 9.7-20.8% for 3-OHBaP, respectively. The developed method was successfully used to measure urinary PAH metabolites of student volunteers in a high school.

Adolescent↗
PubMed2004

Raman spectroscopy of p-hydroxybenzoic acid aqueous solution and surface-unenhanced Raman scattering on silver colloid with ultraviolet excitation.

A high-quality Raman spectrum of p-hydroxybenzoic acid (PHBA) aqueous solution (10(-2) M) under ultraviolet (UV) excitation at 325 nm was obtained, which could not be observed with visible and near infrared (NIR) excitations due to the low concentration in aqueous solution. However, the surface-unenhanced Raman scattering of PHBA in silver colloid excited by ultraviolet was unexpectedly observed, which was quite different from the cases excited with NIR and visible light, by which the SERS effect was very remarkable. This indicated that the SERS of the PHBA-silver colloid system showed selectivity to excitation wavelength. The enhancement mechanisms at different excitation wavelength regions are discussed.

Journal Article↗
PubMed2006

Comparative investigation of the pathogenicity of three Mycobacterium tuberculosis mutants defective in the synthesis of p-hydroxybenzoic acid derivatives.

p-Hydroxybenzoic acid derivatives (p-HBADs) are glycoconjugates secreted by all Mycobacterium tuberculosis isolates whose contribution to pathogenicity remains to be determined. The pathogenicity of three transposon mutants of M. tuberculosis deficient in the biosynthesis of some or all forms of p-HBADs was studied. Whilst the mutants grew similarly to the wild-type strain in macrophages and C57BL/6 mice, two of the mutants induced a more severe and diffuse inflammation in the lungs. The lack of production of some or all forms of p-HBADs in these two mutants also correlated with an increased secretion of the pro-inflammatory cytokines tumour-necrosis factor alpha, interleukin 6 and interleukin 12 in vivo. We propose that the loss of production of p-HBADs by tubercle bacilli results in their diminished ability to suppress the pro-inflammatory response to infection and that this ultimately provokes extensive pulmonary lesions in the C57BL/6 model of tuberculosis infection.

Animals↗
PubMed2004

Solvent effects on infrared spectra of methyl 4-hydroxybenzoate in pure organic solvents and in ethanol/CCl4 binary solvents.

Infrared spectroscopy studies of methyl 4-hydroxybenzoate (MHB) in 17 different organic solvents and in ethanol/CCl4 binary solvent were undertaken to investigate the solvent-solute interactions. The frequencies of carbonyl stretching vibration nu(C=O) of MHB in single solvents were correlated with the solvent acceptor number (AN) and the linear solvation energy relationships (LSER). The assignments of the two bands of nu(C=O) of MHB in alcohols and the single one of that in non-alcoholic solvents were discussed. The shifts of nu(C=O) of MHB in ethanol/CCl4 binary solvents showed that several kinds of solute-solvent hydrogen bonding interactions coexisted in the mixture solvents, with a change in the mole fraction of ethanol in the binary solvents.

Alcohols↗
PubMed2006

3-Hydroxybenzo[a]pyrene in the urine of smokers and non-smokers.

The people studied were male volunteers without occupational and dietary exposure to PAH: 27 smokers (10 cigarettes or more) and 27 non-smokers matched for age and socio-professional category. For each person, all the 24h voided urine samples were reassembled in a single sample. 1-Hydroxypyrene (1-OHPy) and 3-hydroxybenzo[a]pyrene (3-OHBaP) were then determined by automated column-switching high-performance liquid chromatography. Urinary 1-OHPy ranged from 0.041 to 0.530 micromol/molCreatinine (arithmetic mean 0.144, median 0.115) for smokers and from 0.01 to 0.148 mmol/molCreatinine (arithmetic mean 0.044, median 0.032) for non-smokers. These values are close to those of some other studies. Urinary 3-OHBaP ranged from <0.01 to 0.084 nmol/molCreatinine (arithmetic mean 0.030, median 0.023) for smokers and from <0.01 to 0.045 nmol/molCreatinine (arithmetic mean 0.014, median 0.011) for non-smokers. Considering more particularly the urinary 3-OHBaP values, the influence of smoking could be important among workers exposed to low levels of BaP (<100 ng/m(3)) and the concentrations for smokers were equivalent to most of the preshift values of exposed workers. The dietary BaP intake was slightly lower than the BaP intake for an average smoker. From the present study, temporary basic reference levels may be proposed for urinary 3-OHBaP.

Adult↗
PubMed2004

Degradation of 4-hydroxybenzoic acid by combined ultrasound irradiation and catalytic wet peroxide oxidation.

The aim of this study is to explore the potential benefits from the combined use of ultrasound irradiation and catalytic wet peroxide oxidation for the degradation of 4-hydroxybenzoic acid (4-HBA). The target compound degradation was studied under direct and indirect sonication, while silent conditions were employed as reference. The catalyst, a mixed (Al-Fe) pillared clay named FAZA, was in the form of powder and of extrudates. In the case of extrudates it was observed that ultrasound improves the catalyst performance due to reduction of diffusion resistance, thereby increasing the conversion after 4 h by 12-15 times. Increasing the initial concentration of 4-HBA was found to lead to lower conversion. The combined ultrasonic/catalytic process appears very promising for environmental applications.

Journal Article↗