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PubMed1995

The ESR properties, DNA nicking, and DNA association of aged solutions of catechol versus aqueous extracts of tar from cigarette smoke.

Previous studies in our laboratories have shown that extracts from mainstream or sidestream tobacco smoke nick DNA. These solutions contain the tar semiquinone free radical, and the tar radical becomes associated with cellular DNA. Aged solutions of catechol contain a semiquinone species that has ESR properties similar to those of the radical in cigarette tar extracts, and we have used these catechol solutions as a model for the tar radical. Both the radical in aged catechol solutions and the cigarette tar radical become associated with the DNA in mammalian cells and also nick DNA. The nicking of DNA caused by both tar and aged catechol solutions follows saturation kinetics. Aged catechol solutions thus allow the study of a model for the radical present in cigarette tar, without interference from the other toxic constituents in tar extracts.

Animals↗
PubMed1995

Cloning and sequencing of the catechol 2,3-dioxygenase gene of Alcaligenes sp. KF711.

The catechol 2,3-dioxygenase is an aromatic ring-fission enzyme catalyzing the conversion of catechol to 2-hydroxymuconic semialdehyde. A catechol 2,3-dioxygenase gene has been cloned from chromosomal DNA of Alcaligenes sp. KF711, and its sequence was determined. The catechol 2,3-dioxygenase gene was consisted of 927 nucleotides with ATG initiation codon and TGA termination codon, which can encode a polypeptide of molecular weight 35 kDa containing 308 amino acid residues. G+C content of the gene was 58 mol%, and a putative ribosome-binding sequence was identified at about 10 nucleotides upstream from the ATG initiation codon. The sequence of catechol 2,3-dioxygenase from Alcaligenes sp. KF711 exhibited 81-92% homology at nucleotide level and 84-92% homology at amino acid level with those of corresponding enzymes encoded in xylE of TOL plasmid, nahH of NAH7 plasmid, and dmpB of Pseudomonas CF600.

Alcaligenes↗
PubMed1995

Cloning of salicylate hydroxylase gene and catechol 2,3-dioxygenase gene and sequencing of an intergenic sequence between the two genes of Pseudomonas putida KF715.

The salicylate hydroxylase can convert the salicylate to catechol, and catechol 2,3-dioxygenase catalizes the conversion of catechol to 2-hydroxymuconic semialdehyde. A salicylate hydroxylase gene and a catechol 2,3-dioxygenase have been cloned from chromosomal DNA of P. putida KF715. The two genes have different promoters. An open reading frame with 339 nucleotides preceded by a putative ribosome-binding sequence (GGAGG) was identified in the intergenic sequence between salicylate hydroxylase gene and catechol 2,3-dioxygenase gene of P. putida KF715 and its sequence analyzed. This open reading frame can encode a polypeptide of molecular weight 13 kDa containing 112 amino acids, whose sequence exhibited 87% homology with that of ferredoxin encoded in NAH7 of P. putida PpG7 and significant homology with those of redox components in phenol hydroxylase, benzoate 1,2-dioxygenase, toluate 1,2-dioxygenase, xylene monooxygenase, and toluene 4-monooxygenase.

Amino Acid Sequence↗
PubMed1997

Structure of catechol 2,3-dioxygenase gene encoded in TOM plasmid of Pseudomonas cepacia G4.

The catechol 2,3-dioxygenase is an extradiol-type dioxygenase which cleaves the C-C bond at the meta position of catechol to form 2-hydroxymuconic semialdehyde. A catechol 2,3-dioxygenase gene (tomB) in the TOM plasmid of P. cepacia G4 has been cloned and its nucleotide sequence was analyzed. The enzyme gene consisted of 945 base pairs with an ATG initiation codon and a TGA termination codon which can encode a polypeptide of molecular weight 35 kDa containing 314 amino acid residues, and a putative ribosome-binding sequence was identified at approximately 10 nucleotides upstream of the initiation codon. The deduced amino acid sequence of catechol 2,3-dioxygenase from P. cepacia G4 exhibited 79-82% homologies with those of 3-methylcatechol 2,3-dioxygenase of P. putida UCC2 and catechol 2,3-dioxygenase of P. pickettii PKO1.

Amino Acid Sequence↗
PubMed1997

Characterization of the gene encoding catechol 2,3-dioxygenase from Achromobacter xylosoxidans KF701.

Catechol 2,3-dioxygenase (C23O) catalyzes a meta cleavage of the aromatic ring in catechol to form 2-hydroxymuconic semialdehyde. A C23O gene was cloned from chromosomal DNA of A. xylosoxidans KF701, a soil bacterium degrading biphenyl, and expressed in E. coli HB101. In substrate specificity to catechol and its analogs, the C23O exhibited the highest aromatic ring-fission activity to catechol, and its relative activity to other dihydroxylated aromatics was 4-chlorocatechol > 4-methylcatechol > 3-methylcatechol >> 2, 3-dihydroxybiphenyl. Aromatic ring-fission activity of the C23O to catechol was about 40-fold higher than that to 2,3-dihydroxybiphenyl. Nucleotide sequence analysis of the C23O gene from A. xylosoxidans KF701 revealed an open reading frame consisting of 924 base pairs, and identified a putative ribosome-binding sequence (AGGTGA) at about 10 nucleotides upstream from the initiation codon. The open reading frame can encode a polypeptide chain with molecular weight of 34 kDa containing 307 amino acid residues. The deduced amino acid sequence of the C23O exhibited the highest homology with that of C23O from Pseudomonas sp. IC with 96% identity, and the least homology with that of C23O from P. putida F1 with 22% identity among reported C23O sequences. Furthermore, comparison of the C23O sequence with other extradiol dioxygenases has led to identification of evolutionally conserved amino acid residues whose possible catalytic and structural roles are proposed.

Alcaligenes↗
PubMed1988

Catechol estrogen concentrations in maternal and umbilical circulation at different modes of delivery.

To investigate the role of catechol estrogens in human parturition, these steroids were analyzed in samples from the maternal venous and umbilical venous and arterial plasma at vaginal (n = 28) and abdominal (n = 28) delivery. To ensure the appropriateness of collection of umbilical artery and venous blood samples, progesterone content was also determined. Although there is no significant difference in maternal vein content of catechol estrogens between the two groups, the umbilical venous (p = 0.03) and arterial (p = 0.002) plasma concentrations are significantly higher at vaginal delivery than those measured at abdominal delivery. In view of the present data and the importance of catechol estrogens in prostaglandin synthesis and in potentiating the activity of catecholamines through competitive inhibition of catechol-O-methyltransferase, it is suggested that catechol estrogens may play a role in triggering the events involved in the onset of labor and delivery in humans.

Cesarean Section↗
PubMed1983

Colorimetric determination of catechol siderophores in microbial cultures.

A highly sensitive spectrophotometric method for the selective detection of catechol compounds such as catechol siderophores (e.g., enterobactin) is described. The basis of the method involves the ability of the vicinal aromatic hydroxyl groups under acidic conditions to bring about a reduction of Fe3+ (from ferric ammonium citrate) to Fe2+. Detection of Fe2+ in the presence of Fe3+ is made with 1,10-phenanthroline under previously established conditions. The assay mixture is heated at 60 degrees C for 1 h to accelerate the development of color which is subsequently measured at 510 nm. The Beer-Lambert law is obeyed over the range of 0.16 to 60 microM 2,3-dihydroxybenzoic acid. Compared to the Arnow nitration method, the assay is more responsive, is approximately seven times more sensitive, and is effective with catechols substituted at positions 3 and 4. The method gives positive results with catechols such as DL-DOPA, L-dopamine, (+/-)-epinephrine, and DL-norepinephrine. Very rapid color development is obtained with ascorbic acid and p-diols, while m-diols are poorly detected. Low degrees of reactivity are shown by hydroxylamino and hydroxamate compounds. Phenolic, sulfydryl, indolyl, and quinonyl derivatives do not interfere with the reaction. The method has been adapted to determine catechol compounds in the culture medium of bacterial cells grown at different iron concentrations.

Catechols↗
PubMed1982

Substrate stereospecificity and selectivity of catechol-O-methyltransferase for DOPA, DOPA derivatives and alpha-substituted catecholamines.

The substrate specificity of highly purified pig liver catechol-O-methyltransferase has been investigated kinetically. This enzyme shows stereospecificity towards the naturally occurring L-isomer of 3,4-dihydroxyphenylalanine (DOPA) which has a higher affinity and maximal velocity as a substrate than the D-form. We have confirmed the implication of the in vivo study of Ito et al. [1], that methylation of 5-S-L-cysteinyl-L-DOPA is catalysed extremely slowly by catechol-O-methyltransferase, despite the comparatively high affinity of the enzyme for the substrate. Salbutamol is not a substrate for the enzyme and DL-threo-3,4-dihydroxyphenylserine (DOPS) is such a poor substrate that accurate kinetic analysis proved impossible. Alpha-substitution of DOPA, noradrenaline and isoprenaline causes a decrease in the affinity of catechol-O-methyltransferase for these compounds. However, the "suicide' inhibitors of aromatic-L-amino acid decarboxylase (DOPA decarboxylase), fluoro- and difluoro-alpha-methyl DOPA are more superior catechol-O-methyltransferase substrates than alpha-methyl DOPA, presumably because the electron-withdrawing effect of the presence of fluorine in their structure overcomes the steric influence of the alpha-methyl group. A DOPA decarboxylase inhibitor in clinical use, benserazide, is, however, a much superior catechol-O-methyltransferase substrate and may have the therapeutic advantage of decreasing methylation of L-DOPA [2]. Alpha-Methyl dopamine has a lower Km and higher Vmax than the parent compound.

Animals↗
PubMed1983

Catechol estrogens and the control of gonadotropin and prolactin secretion in man.

The catechol estrogens, the 2- or 4-hydroxylated metabolites of estrone and estradiol, have pharmacologic properties of both estrogens and catecholamines and are formed from estrogens in peripheral tissues and in the brain. This has led to speculation that they may mediate some of the feedback effects of estrogens upon gonadotropins and prolactin (PRL). Studies testing these hypotheses are still few and have not been conclusive. There have been reports that the catechol estrogen 2-hydroxyestrone (2-OHE1) might act as a partial estrogen antagonist, stimulating gonadotropin secretion; and that it might have dopamine-like effects, suppressing the secretion of PRL. In studies testing the chronic and acute effects of catechol estrogens on LH, FSH, and PRL in men and women, we found that they behaved as estrogens, suppressing gonadotropins when given in doses high enough to compensate for their rapid clearance and degradation. We found no evidence that they suppress PRL secretion. The weight of available evidence suggests that these effects are mediated by estrogen receptor interactions; and that the formation of catechol estrogens is not an obligatory step in the feedback effects of estrogens, although it may have a modulatory role. Plasma levels of catechol estrogens are too low for them to exert circulating neuroendocrine effects.

Animals↗
PubMed1986

Protection of rat hepatocytes from tert-butyl hydroperoxide-induced injury by catechol.

Metabolism of tert-butyl hydroperoxide (TBHP, 2.0 mM) by glutathione peroxidase within isolated rat hepatocytes caused a rapid oxidation of intracellular reduced glutathione and ultimately NADPH through glutathione reductase. TBHP also caused the formation of surface blebs in the hepatocyte plasma membrane followed by the leakage of cytosolic enzymes, such as lactate dehydrogenase, into the incubation medium. Catechol (0.1 mM) protected hepatocytes from the cytotoxic effects of TBHP but did not prevent the rapid oxidation of glutathione indicating normal metabolism of TBHP through glutathione reductase. In contrast, addition of catechol to the hepatocyte incubations prevented TBHP-induced depletion of intracellular NADPH and increased the total NADP+ + NADPH concentration without altering significantly the intracellular NADP+ content or the NADPH/NADP + NADPH ratio. Catechol did not alter TBHP stimulation of the pentose phosphate pathway. Hepatocytes incubated with sublethal concentrations of TBHP (1.0 mM) did not leak lactate dehydrogenase into the medium but did lose intracellular potassium. In these experiments, TBHP caused a sustained increase in phosphorylase alpha activity suggesting that TBHP metabolism may be associated with a sustained increase in cytosolic free Ca2+. In the presence of catechol, phosphorylase alpha activity was increased by 5 min but returned toward control by 20 min. These data suggest that catechol may be protecting hepatocytes from TBHP-induced injury by preventing a sustained rise in cytosolic free Ca2+ concentration.

Animals↗
PubMed1982

Hydroquinone and catechol reduce the frequency of progenitor B lymphocytes in mouse spleen and bone marrow.

Hydroquinone and catechol are two metabolites of benzene that are potential inducers of hematotoxicity. We investigated the in vivo toxicity of these metabolites toward the development of polyclonal, plaque-forming cells (PC-PFC) from progenitor B lymphocytes. Dextran sulfate (DxS), lipopolysaccharide (LPS), or the two mitogens combined (DxS + LPS) were used to induce proliferation and maturation of these progenitors to PC-PFC. Groups of 4 C57BL/6 mice were exposed to 2 daily doses, either intravenously or intraperitoneally, of hydroquinone (100 mg/kg) or catechol (75 mg/kg) for 3 consecutive days. Spleen and marrow cells were harvested for culture 1 day later. The results demonstrated that both metabolites were cytotoxic to spleen cells. Hydroquinone (100 mg/kg) also reduced marrow cellularity, whereas catechol (75 mg/kg) did not significantly affect marrow cellularity. Each compound reduced the frequency of PC-PFC developed from the spleens and marrows of treated mice, but only catechol selectively inhibited the maturation of LPS-activated marrow progenitors into end-stage PC-PFC. These experiments demonstrate the immunotoxic potential of hydroquinone and catechol in vivo through the reduction of progenitor B lymphocytes and suggest that inhibition of precursor cell maturation may play a significant role in the hematotoxicity observed after chronic exposure to benzene.

Animals↗
PubMed1983

Mutagenicity and co-mutagenicity of catechol on Salmonella.

Catechol was not mutagenic for Salmonella typhimurium TA98, TA100 or TA1537 in the presence or absence of S9 mix. At the lower level of S9 in the Ames method, the mutagenic activity of benzo[a]pyrene decreased with the increased addition of catechol. When catechol was added to the pre-incubation mixture at a higher concentration than in the conventional Ames method, the mutagenic activity of benzo[a]pyrene increased with the increased addition of catechol. Catechol is believed to be a co-mutagen for benzo[a]pyrene in the presence of a sufficient amount of S9 in the incubation mixture.

Benzopyrenes↗
PubMed1988

The A-type potassium current: catechol-induced blockage in snail neurons.

The effects of catechol (1-12.5 mM) on membrane properties, action potential and membrane ionic currents were investigated in identified snail neurons under current- and voltage-clamp conditions. Catechol hardly influenced the resting membrane potential, or the action potential amplitude and duration, but it increased the spike voltage threshold and slightly decreased the input resistance. Catechol specifically decreased the amplitude of the potassium A-currents in a dose-dependent way (Kd = 5 mM), without significant modulation of other potassium currents. The time constants of decay of A-current increased and the steady-state activation or inactivation curve shifted to more positive potentials in the catechol solutions. The blocking effect of catechol on A-currents followed a one-to-one binding stoichiometry (nH = 0.8).

Action Potentials↗
PubMed1991

Catechol blocks the fast outward potassium current in melanotrophs of the rat pituitary.

The effect of catechol on the fast voltage-gated K+ current (IK(f)) of acutely dissociated rat melanotrophs was investigated in whole-cell recordings. Half-maximal inhibition of IK(f) occurred at an external concentration of 1.7 mM and this effect was associated with a decrease of the rate of the current decay. Internal catechol had no measurable effect on IK(f). Catechol appeared to be equally effective as a blocker of the slow voltage-gated K+ current (IK(s)). Despite this lack of specificity the blocking action of catechol was voltage- and frequency-independent and was rapidly reversible. Catechol therefore represents a useful alternative to 4-aminopyridine as a blocker of IK(f).

Animals↗
PubMed2005

Structure of catechol 1,2-dioxygenase from Pseudomonas arvilla.

Catechol 1,2-dioxygenase was first studied by Hayaishi and colleagues in 1950. In 1967, catechol 1,2-dioxygenase from Pseudomonas arvilla C-1 (PaCTD) was chosen as a model system for the catecholic intradiol dioxygenases due to its activity, stability and expression level. Here we report the 2.65 A structure of the betabeta isozyme of PaCTD. The structure supports the hypothesis first made by Vetting and Ohlendorf [The 1.8A crystal structure of catechol 1,2-dioxygenase reveals a novel hydrophobic helical zipper as a subunit linker, Struct. Fold. Des. 8 (2000) 429-440.] that the catechol 1,2-dioxygenases are lipid binding proteins. The 5 amino-terminal helices involved in dimerization and forming the lipid binding site are shown to be plastic in their positions and orientations. The sequence differences between the alpha and beta polypeptides are located at the part of the monomers distant from dimerization surface and thus permit the formation of the 3 isozymes (alphaalpha, alphabeta, and betabeta) of PaCTD. The reported inactivation by sulfhydryl-modifying reagents is explained by the structure. The 10-residue Helix F (residues 203-212) is proposed to be central in communicating between the lipid binding site and the active site.

Amino Acid Sequence↗
PubMed2005

A linear correlation between energy of LMCT band and oxygenation reaction rate of a series of catecholatoiron(III) complexes: initial oxygen binding during intradiol catechol oxygenation.

The oxygen reactivity of catecholatoiron(III) complexes has been examined using a series of catecholate ligands as the substrate. All the complexes examined here, [Fe(III)(TPA)(R-Cat)]BPh(4) (1-9) (TPA: tris(pyridin-2-ylmethyl)amine; R-Cat: substituted catecholate ligand, R=3,5-(t)Bu(2) (1), 3,6-(t)Bu2 (2), 3,5-Me2 (3), 3,6-Me2 (4), 4-(t)Bu (5), 4-Me (6), H (7), 4-Cl (8) and 3-Cl (9)), exclusively afforded the intradiol cleaving products of the catecholate ligands upon exposure to O2. It was revealed that 1-7 can be categorized into two classes based on their electrochemical properties; i.e., the complexes having the dialkyl-substituted (group A) and the mono- or non-substituted (group B) catecholate ligands. In spite of their classification, these two groups show a linear correlation between the logarithm of the reaction rate constant with O2 and the energy of the catecholate-to-iron(III) LMCT band, although 2 shows a large negative deviation from the correlation line. Based on this LMCT-energy dependent reactivity of 1 and 3-9 as well as the very low reactivity of 2, we have discussed on the mechanisms of the reaction of [Fe(III)(TPA)(R-Cat)]BPh4 with O2.

Catechols↗
PubMed2005

Synthesis of the catechols of natural and synthetic estrogens by using 2-iodoxybenzoic acid (IBX) as the oxidizing agent.

A method for the synthesis of 2-hydroxyestrone/estradiol, 4-hydroxyestrone/estradiol, 3'-hydroxydiethylstilbestrol, 3'-hydroxyhexestrol, and 3'-hydroxydienestrol is reported, in which 2-iodoxybenzoic acid (IBX) and the corresponding phenolic estrogen are reacted. Treatment of the natural estrogens, estrone/estradiol, with stoichiometric amounts of IBX in dimethylformamide initially yielded a mixture of estrone/estradiol-2,3- and -3,4-quinones, which were reduced in situ to the corresponding catechols by treatment with a 1 M aqueous solution of ascorbic acid. Chromatographic separation of the reaction products afforded 2- and 4-hydroxyestrone/estradiol in good overall yields (79%). In the case of the synthetic estrogens containing two identical phenolic rings, protection of one ring is a prerequisite for the synthesis of the monocatechol. Thus, diethylstilbestrol and dienestrol were protected at one phenol ring as their methyl ethers. The resulting monophenols were treated with stoichiometric amounts of IBX for 1 h, followed by treatment with 1 M aqueous ascorbic acid to obtain the corresponding catechols in more than 70% yield. Furthermore, the catechol of diethylstilbestrol, protected at one ring, was reduced by catalytic hydrogenation at the C3-C4 double bond to obtain 3'-hydroxyhexestrol in 90% yield. Removal of the protected methoxy groups of the synthetic estrogen catechols was carried out by treatment with a 1 M solution of boron tribromide in dichloromethane. This method is highly efficient for the preparative scale synthesis of catechols of both natural and synthetic estrogens.

Boron↗
PubMed2003

Hydroquinone and catechol interfere with T cell cycle entry and progression through the G1 phase.

Cigarette smoking causes profound suppression of pulmonary T cell responses, which is associated with increased susceptibility to respiratory tract infections and decreased tumor surveillance. Hydroquinone (HQ) and catechol, at concentrations comparable to those found in cigarette smoke, are potent inhibitors of T cell activation and proliferation. We have previously shown that HQ and catechol inhibit ribonucleotide reductase, the rate-limiting enzyme in DNA synthesis. In this report we demonstrate that HQ and catechol also inhibit blastogenesis by interfering with T cell cycle entry and progression through the G(1) phase. In an attempt to localize the point in the cell cycle where arrest occurred, a set of key markers of activation and cell cycle progression were examined, including induction of c-Myc, up regulation of RNA synthesis, surface expression of CD71, and induction of E2F-dependent gene expression. Addition of HQ or catechol prior to stimulation inhibited each of these events without decreasing cell viability. However, production of IL-2 and surface expression of CD69 and CD25 were not affected, indicating that HQ and catechol inhibit only certain cell cycle events. These studies provide further indication of the regulatory pathways by which cigarette smoke inhibits T cell responses in the lungs of smokers.

Antigens, CD↗