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PubMed1971

Enzymic formation of p-hydroxybenzoate from p-hydroxycinnamate.

An enzyme that converts p-hydroxycinnamate into p-hydroxybenzoate was found in rat liver. It is localized in the mitochondria and requires ATP. The activity is lost when the mitochondria are stored frozen overnight. Addition of magnesium chloride, cytochrome c, GSH, coenzyme A or potassium cyanide did not have any effect on the activity. When the rats were fed with alpha-p-chlorophenoxyisobutyrate, the rate of formation of p-hydroxybenzoate increased twofold. The reaction has some similar properties to fatty acid oxidation, but appears to be different in many respects.

Adenosine Triphosphate↗

PubMed1973

Polyprenyl pyrophosphate-p-hydroxybenzoate polyprenyltransferase activity in mitochondria of broad-bean seeds and yeast.

Cell-free homogenates prepared from broad-bean seeds and yeast cells are capable of synthesizing 4-carboxy-2-polyprenylphenols from p-hydroxybenzoate and either isopentenyl pyrophosphate or protein-bound polyprenyl pyrophosphates (produced by incubating a Micrococcus lysodeikticus extract with isopentenyl pyrophosphate). The mitochondria contained all the polyprenyl pyrophosphate-p-hydroxybenzoate polyprenyltransferase activity; however, unlike the homogenates they could not synthesize a side chain from isopentenyl pyrophosphate and had to be provided with protein-bound polyprenyl pyrophosphates.

Benzoates↗

PubMed2000

Purification and properties of hydroquinone hydroxylase, a FAD-dependent monooxygenase involved in the catabolism of 4-hydroxybenzoate in Candida parapsilosis CBS604.

The ascomycetous yeast Candida parapsilosis CBS604 catabolizes 4-hydroxybenzoate through the initial formation of hydroquinone (1, 4-dihydroxybenzene). High levels of hydroquinone hydroxylase activity are induced when the yeast is grown on either 4-hydroxybenzoate, 2,4-dihydroxybenzoate, 1,3-dihydroxybenzene or 1, 4-dihydroxybenzene as the sole carbon source. The monooxygenase constitutes up to 5% of the total amount of protein and is purified to apparent homogeneity in three chromatographic steps. Hydroquinone hydroxylase from C. parapsilosis is a homodimer of about 150 kDa with each 76-kDa subunit containing a tightly noncovalently bound FAD. The flavin prosthetic group is quantitatively resolved from the protein at neutral pH in the presence of chaotropic salts. The apoenzyme is dimeric and readily reconstituted with FAD. Hydroquinone hydroxylase from C. parapsilosis catalyzes the ortho-hydroxylation of a wide range of monocyclic phenols with the stoichiometric consumption of NADPH and oxygen. With most aromatic substrates, no uncoupling of hydroxylation occurs. Hydroxylation of monofluorinated phenols is highly regiospecific with a preference for C6 hydroxylation. Binding of phenol highly stimulates the rate of flavin reduction by NADPH. At pH 7.6, 25 degrees C, this step does not limit the rate of overall catalysis. During purification, hydroquinone hydroxylase is susceptible towards limited proteolysis. Proteolytic cleavage does not influence the enzyme dimeric nature but results in relatively stable protein fragments of 55, 43, 35 and 22 kDa. N-Terminal peptide sequence analysis revealed the presence of two nick sites and showed that hydroquinone hydroxylase from C. parapsilosis is structurally related to phenol hydroxylase from Trichosporon cutaneum. The implications of these findings for the catalytic mechanism of hydroquinone hydroxylase are discussed.

Amino Acid Sequence↗

PubMedDate not supplied

An apparent anti-Jka reacting only in the presence of methyl esters of hydroxybenzoic acid.

An apparent anti-Jka, reacting only in the presence of methyl esters of hydroxybenzoic acid (HBA), was detected in an individual with Jk (a+) red blood cells. The antibody was first detected when a commercial low-ionic-strength-solution preparation containing the preservative methyl paraben (a methyl ester of hydroxybenzoic acid) was used in compatibility testing. Negative reactions were obtained when regular saline, albumin, and enzyme technics were employed. The positive indirect antiglobulin tests were due to cell-bound complement; no IgG was detected. The patient had no clinical or hematologic evidence of hemolytic anemia and was transfused with Jk(a+) red blood cells with no ill effects. It is postulated that immune complexes formed between the antibody and the chemical may result in a site complementary to some aspect of the Jka antigen. When this complex binds to Jk(a+) cells, complement is activated and some complement components remain on the cells. We do not know why only Jk(a+) cells were involved in these reactions.

Antigen-Antibody Complex↗

PubMed2003

Purification and characterization of PrbA, a new esterase from Enterobacter cloacae hydrolyzing the esters of 4-hydroxybenzoic acid (parabens).

The esterase PrbA from Enterobacter cloacae strain EM has previously been shown to confer additional resistance to the esters of 4-hydroxybenzoic acid (parabens) to two species of Enterobacter. The PrbA protein has been purified from E. cloacae strain EM using a three-step protocol resulting in a 60-fold increase in specific activity. The molecular mass of the mature enzyme was determined to be 54,619 +/- 1 Da by mass spectrometry. It is highly active against a series of parabens with alkyl groups ranging from methyl to butyl, with K(m) and V(max) values ranging from 0.45 to 0.88 mM and 0.031 to 0.15 mM/min, respectively. The K(m) and V(max) values for p-nitrophenyl acetate were 3.7 mM and 0.051 mM/min. PrbA hydrolyzed a variety of structurally analogous compounds, with activities larger than 20% relative to propyl paraben for methyl 3-hydroxybenzoate, methyl 4-aminobenzoate, or methyl vanillate. The enzyme showed optimum activity at 31 degrees C and at pH 7.0. PrbA was able to transesterify parabens with alcohols of increasing chain length from methanol to n-butanol, achieving 64% transesterification of 0.5 mm propyl paraben with 5% methanol within 2 h. PrbA was inhibited by 1-chloro-3-tosylamido-4-phenyl-2-butanone and 1-chloro-3-tosylamido-7-amino-2-heptanone (TLCK), with K(i) values of 0.29 and 0.20 mM, respectively, and was irreversibly inhibited by Diisopropyl fluorophosphate (DFP) or diethyl pyrocarbonate. The stoichiometry of addition of DFP to the enzyme was 1:1 and only 1 TLCK molecule was found in TLCK-modified enzyme, as measured by mass spectrometry. Analysis of the tryptic digest of the DFP-modified PrbA demonstrated that the addition of a DFP molecule occurred at Ser-189, indicating the location of the active serine.

Amino Acid Sequence↗

PubMed1985

Secondary metabolites of benzo[a]pyrene: 3-hydroxy-trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene, a biliary metabolite of 3-hydroxybenzo[a]pyrene in the rat.

Rats administered 3-hydroxybenzo[a]pyrene (50 mg/kg, i.p.), excrete via the bile metabolites which, after treatment with beta-glucuronidase and aryl sulphatase, yield, in addition to 3-hydroxybenzo[a]pyrene, 3-hydroxy-trans-7,8-dihydro-7,8-dihydroxybenzo[a]pyrene (3-OH-BP-7,8-diol) and a minor, highly labile, metabolite tentatively identified as 3,5-dihydroxybenzo[a]pyrene. These novel metabolites are readily isolated in a pure state via preparative layer chromatography. The structure of the 3-OH-BP-7,8-diol was revealed by its u.v., proton magnetic resonance and mass spectral properties. Its hydroxyl functions are in a predominantly quasi-diequatorial conformation.

Animals↗

PubMed1986

Reactive intermediates from 3-hydroxybenzo[a]pyrene and its glucuronide.

3-Hydroxybenzo[a]pyrene (3-OH-BaP) is oxidized by the horseradish peroxidase/H2O2 system to benzo[a]pyrene-3,6-quinone. In the presence of N-acetylcysteine one other product is also formed. This was identified by its chemical, and u.v., mass and n.m.r. spectral properties as 6-(H-acetyl-cystein-S-yl)-3-hydroxybenzo[a]pyrene (6-NAc-cys-3-OH-BaP). Replacement of the N-acetylcysteine by glutathione leads to the formation of a 3-OH-BaP-glutathione adduct. Enzymic hydrolysis of benzo[a]pyrene-3-glucuronide in the presence of N-acetylcysteine yields, in addition to 3-OH-BaP, a product which co-chromatographs with 6-NAc-cys-3-OH-BaP and has identical chemical and spectral characteristics.

Acetylcysteine↗

PubMed2006

Functional characterization of OsPPT1, which encodes p-hydroxybenzoate polyprenyltransferase involved in ubiquinone biosynthesis in Oryza sativa.

Prenylation of the aromatic intermediate p-hydroxybenzoate (PHB) is a critical step in ubiquinone (UQ) biosynthesis. The enzyme that catalyzes this prenylation reaction is p-hydroxybenzoate polyprenyltransferase (PPT), which substitutes an aromatic proton at the m-position of PHB with a prenyl chain provided by polyprenyl diphosphate synthase. The rice genome contains three PPT candidates that share significant similarity with the yeast PPT (COQ2 gene), and the rice gene showing the highest similarity to COQ2 was isolated by reverse transcription-PCR and designated OsPPT1a. The deduced amino acid sequence of OsPPT1a contained a putative mitochondrial sorting signal at the N-terminus and conserved domains for putative substrate-binding sites typical of PPT protein family members. The subcellular localization of OsPPT1a protein was shown to be mainly in mitochondria based on studies using a green fluorescent protein-PPT fusion. A yeast complementation study revealed that OsPPT1a expression successfully recovered the growth defect of the coq2 mutant. A prenyltransferase assay using recombinant protein showed that OsPPT1a accepted prenyl diphosphates of various chain lengths as prenyl donors, whereas it showed strict substrate specificity for the aromatic substrate PHB as a prenyl acceptor. The apparent K (m) values for geranyl diphosphate and PHB were 59.7 and 6.04 microM, respectively. The requirement by OsPPT1a and COQ2 for divalent cations was also studied, with Mg2+ found to produce the highest enzyme activity. Northern analysis showed that OsPPT1a mRNA was accumulated in all tissues of O. sativa. These results suggest that OsPPT1a is a functional PPT involved in UQ biosynthesis in O. sativa.

Alkyl and Aryl Transferases↗

PubMed1994

Formation of 4-hydroxybenzoate in Escherichia coli: characterization of the ubiC gene and its encoded enzyme chorismate pyruvate-lyase.

Chorismate pyruvate-lyase from Escherichia coli converts chorismate to 4-hydroxybenzoate. The enzyme was enriched 3000-fold by overexpression and chromatographic purification. It has an apparent Km value for chorismate of 6.1 microM and an isoelectric point of pH 6.45. The enzyme activity did not require metal cofactors. Promoter sequences in the 5' flanking sequences of the ubiCA operon were localized by transcription and translation of active chorismate pyruvate-lyase in vitro from different PCR fragments. Sequencing of the ubiC gene of the mutant strain AN244 revealed a G-->A transition resulting in a change from glutamic acid to lysine. A feeding experiment with [1,7-13C2]shikimate confirmed the chorismate pyruvate-lyase as the sole enzymic source of 4-hydroxybenzoate in vivo.

Bacterial Proteins↗

PubMed1993

Ciliotoxicity of methyl- and propyl-p-hydroxybenzoates: a dose-response and surface-response study.

The effect of methyl-p-hydroxybenzoate (methyl paraben, MHB) and propyl-p-hydroxybenzoate (propyl paraben, PHB) on ciliary beat frequency was investigated using surface-response methodology. Both compounds are shown to be ciliotoxic at concentrations equal to or lower than those in use for preserving aqueous formulations. The dose-response curves show the typical sigmoidal pattern. Interaction by the two compounds is evidenced by the curved response surface for ciliotoxicity.

Animals↗

PubMed2001

Hydrolysis of 4-hydroxybenzoic acid esters (parabens) and their aerobic transformation into phenol by the resistant Enterobacter cloacae strain EM.

Enterobacter cloacae strain EM was isolated from a commercial dietary mineral supplement stabilized by a mixture of methylparaben and propylparaben. It harbored a high-molecular-weight plasmid and was resistant to high concentrations of parabens. Strain EM was able to grow in liquid media containing similar amounts of parabens as found in the mineral supplement (1,700 and 180 mg of methyl and propylparaben, respectively, per liter or 11.2 and 1.0 mM) and in very high concentrations of methylparaben (3,000 mg liter(-1), or 19.7 mM). This strain was able to hydrolyze approximately 500 mg of methyl-, ethyl-, or propylparaben liter(-1) (3 mM) in less than 2 h in liquid culture, and the supernatant of a sonicated culture, after a 30-fold dilution, was able to hydrolyze 1,000 mg of methylparaben liter(-1) (6.6 mM) in 15 min. The first step of paraben degradation was the hydrolysis of the ester bond to produce 4-hydroxybenzoic acid, followed by a decarboxylation step to produce phenol under aerobic conditions. The transformation of 4-hydroxybenzoic acid into phenol was stoichiometric. The conversion of approximately 500 mg of parabens liter(-1) (3 mM) to phenol in liquid culture was completed within 5 h without significant hindrance to the growth of strain EM, while higher concentrations of parabens partially inhibited its growth.

Biodegradation, Environmental↗

PubMed2003

Genetic engineering of a highly solvent-tolerant Pseudomonas putida strain for biotransformation of toluene to p-hydroxybenzoate.

The solvent-tolerant strain Pseudomonas putida DOT-T1E has been engineered for biotransformation of toluene into 4-hydroxybenzoate (4-HBA). P. putida DOT-T1E transforms toluene into 3-methylcatechol in a reaction catalyzed by toluene dioxygenase. The todC1C2 genes encode the alpha and beta subunits of the multicomponent enzyme toluene dioxygenase, which catalyzes the first step in the Tod pathway of toluene catabolism. A DOT-T1EdeltatodC mutant strain was constructed by homologous recombination and was shown to be unable to use toluene as a sole carbon source. The P. putida pobA gene, whose product is responsible for the hydroxylation of 4-HBA into 3,4-hydroxybenzoate, was cloned by complementation of a Pseudomonas mendocina pobA1 pobA2 double mutant. This pobA gene was knocked out in vitro and used to generate a double mutant, DOT-T1EdeltatodCpobA, that was unable to use either toluene or 4-HBA as a carbon source. The tmo and pcu genes from P. mendocina KR1, which catalyze the transformation of toluene into 4-HBA through a combination of the toluene 4-monoxygenase pathway and oxidation of p-cresol into the hydroxylated carboxylic acid, were subcloned in mini-Tn5Tc and stably recruited in the chromosome of DOT-T1EdeltatodCpobA. Expression of the tmo and pcu genes took place in a DOT-T1E background due to cross-activation of the tmo promoter by the two-component signal transduction system TodST. Several independent isolates that accumulated 4-HBA in the supernatant from toluene were analyzed. Differences were observed in these clones in the time required for detection of 4-HBA and in the amount of this compound accumulated in the supernatant. The fastest and most noticeable accumulation of 4-HBA (12 mM) was found with a clone designated DOT-T1E-24.

Biotransformation↗

PubMed1990

Selection of Acinetobacter calcoaceticus mutants deficient in the p-hydroxybenzoate hydroxylase gene (pobA), a member of a supraoperonic cluster.

p-Hydroxybenzoate hydroxylase, the product of the pobA gene, gives rise to protocatechuate, which is metabolized by enzymes encoded by the pca operon in Acinetobacter calcoaceticus. Mutations in pcaD prevented growth of A. calcoaceticus with succinate in the presence of p-hydroxybenzoate. Mutants selected on this medium contained the original mutation in pcaD and also carried spontaneous mutations in pobA. These independently expressed genes were cotransformed with a frequency of 15% and thus are components of a supraoperonic cluster.

Acinetobacter↗

PubMed1994

Characterization of the pcaR regulatory gene from Pseudomonas putida, which is required for the complete degradation of p-hydroxybenzoate.

The pca branch of the beta-ketoadipate pathway in Pseudomonas putida is responsible for the complete degradation of p-hydroxybenzoate through ortho cleavage of the initial pathway metabolite, protocatechuate. The pcaR regulatory locus has been found to be required for both induction of all of the genes within the pca regulon (pcaBDC, pcaIJ, and pcaF) and the chemotactic response of the bacteria to aromatic compounds. Insertional inactivation mutagenesis, using Tn5 and mini-Tn5 transposons, was used to locate, clone, and sequence this pcaR regulatory gene. The pcaR gene product, when overexpressed in Escherichia coli, possessed a specific affinity for the pcaIJ promoter region and demonstrated that the entire PcaR protein was required for this function. The deduced amino acid sequence of the PcaR regulatory peptide bears little resemblance to its counterpart in the other branch of the pathway, CatR, but exhibits significant homology to its regulatory antecedent, PobR, which regulates the initial breakdown of p-hydroxybenzoate into protocatechuate. Comparisons of the pcaIJ and pcaR promoter regions revealed conservation of a 15-bp sequence centered around the -10 region in both sequences. This, together with previously defined deletional studies with the pcaIJ promoter region, suggests that PcaR exerts its regulatory effect through protein-DNA interactions within this region, which would be unusually close to the transcriptional start site of pcaIJ for a positive regulator.

Amino Acid Sequence↗

PubMed1969

Biosynthesis of ubiquinone in Escherichia coli K-12: location of genes affecting the metabolism of 3-octaprenyl-4-hydroxybenzoic acid and 2-octaprenylphenol.

Two genes (ubiB and ubiD) concerned with two successive reactions in ubiquinone biosynthesis in Escherichia coli were mapped and found to be closely linked. Mutant strains of E. coli carrying the ubiB(-) and ubiD(-) alleles were shown to accumulate 2-octaprenylphenol and 3-octaprenyl-4-hydroxybenzoic acid, respectively. These compounds were isolated and identified by using nuclear magnetic resonance and mass and infrared spectroscopy. Cell extracts from the mutant strain carrying the ubiD(-) allele lack 3-octaprenyl-4-hydroxybenzoate decarboxylase activity.

Benzoates↗

PubMed1998

Antimicrobial activity of 4-hydroxybenzoic acid and trans 4-hydroxycinnamic acid isolated and identified from rice hull.

Two antimicrobial substances in rice hull were isolated and identified as 4-hydroxybenzoic acid and trans 4-hydroxycinnamic acid by LC-MS, and 1H- and 13C-NMR. An evaluation of 50% inhibition of growth (IC50) revealed that the two substances had different inhibition profiles against various microorganisms. Most of the gram-positive and some gram-negative bacteria were sensitive to trans 4-hydroxycinnamic acid and 4-hydroxybenzoic acid at IC50 concentrations of 100-170 and 160 micrograms/ml, respectively.

Anti-Bacterial Agents↗

PubMed1984

Pharmacokinetic pilot study with imidazole 2-hydroxybenzoate using new analytical methods.

Imidazole 2-hydroxybenzoate is a new antiphlogistic compound with analgesic and antipyretic properties undergoing clinical investigations. The purpose of this pilot study was to evaluate new methods for the quantitation of imidazole, salicylic acid and salicyluric acid in plasma and urine. Imidazole metabolites caused considerable methodologic difficulties in plasma and urine. They were below the detectable limit. Salicylic acid metabolites were present in plasma also under the limit of detection (0.5 microgram/ml). In urine the metabolite salicyluric acid was measured in considerable quantities, whereas gentisinic acid was under the limit of detection. Three healthy volunteers were given a single p.o. dose of 750 mg imidazole 2-hydroxybenzoate in order to examine the practicability of these new methods a well as to evaluate the pharmacokinetics. The data are presented and interpreted. Further studies in this respect are advised.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1976

Lack of carcinogenicity of 4-, 5-, 6-, 7-, 8-, 9-, and 10-hydroxybenzo(a)pyrene on mouse skin.

Seven phenols of benzo(a)pyrene (4-, 5-, 6-, 7-, 8-, 9-, and 10-hydroxybenzo(a)pyrene) were tested for carcinogenicity on mouse skin by application of 0.4 mumole of compound once every two weeks for 56 weeks. None of the seven phenols tested was carcinogenic to mouse skin, while treatment with the same dose of benzo(a)pyrene produced tumors in 92% of the treated animals. The lack of carcinogenicity of 7- and 8-hydroxybenzo(a)pyrene indicates that the strong carcinogenic activity previously reported for benzo(a)pyrene 7,8-oxide was not due to either phenolic isomerization product of this arene oxide.

Animals↗