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PubMed2000

Catechol-binding serines of beta(2)-adrenergic receptors control the equilibrium between active and inactive receptor states.

The binding free energy for the interaction between serines 204 and 207 of the fifth transmembrane helix of the beta(2)-adrenergic receptor (beta(2)-AR) and catecholic hydroxyl (OH) groups of adrenergic agonists was analyzed using double mutant cycles. Binding affinities for catecholic and noncatecholic agonists were measured in wild-type and mutant receptors, carrying alanine replacement of the two serines (S204A, S207A beta(2)-AR), a constitutive activating mutation, or both. The free energy coupling between the losses of binding energy attributable to OH deletion from the ligand and from the receptor indicates a strong interaction (nonadditivity) as expected for a direct binding between the two sets of groups. However, we also measured a significant interaction between the deletion of OH groups from the receptor and the constitutive activating mutation. This suggests that a fraction of the decrease in agonist affinity caused by serine mutagenesis may involve a shift in the conformational equilibrium of the receptor toward the inactive state. Direct measurements using a transient transfection assay confirm this prediction. The constitutive activity of the (S204A, S207A) beta(2)-AR mutant is 50 to 60% lower than that of the wild-type beta(2)-AR. We conclude that S204 and S207 do not only provide a docking site for the agonist, but also control the equilibrium of the receptor between active (R*) and inactive (R) forms.

Amino Acid Substitution↗
PubMed2000

[Cloning of a new catechol 1,2-dioxygenase gene (tfd C) from Plesiomonas and its expression in the E. coli].

A new catechol-1,2-dioxygenase gene (tfd C) was cloned from the Plesiomonas using the PCR method. Primers were designed according to the reported sequence of Catechol-1,2-dioxygenase (C120) gene from Alcaligenes eutroplus. The amplified fragment contained a 765 bp open reading frame (ORF), encoding a protein of 255 amino acids. The new tfd C gene shared a high homology with the one cloned from Alcaligenes eutroplus, showing only one base difference at 693 site (C-->A) and consequently one amino acid difference at 228 site (P-->T). The ORF was cloned to the plasmid pBluescriptII KS, which was transferred to E. coli JM109 and a positive clone, pBt2G, was then selected. A significant activity of C120 was detected in the positive clone. When the ORF was cloned to the plasmid pET-30a, which was transferred to E. coli BL21(DE3) plysS, the expected 33 kD protein was detected from a positive clone, pET30A, by SDS-PAGE. The C120 is a key enzyme in degrading aromatic pollutants in the environment. In order to use plants to degrade aromatic pollutants, the gene will be introduced into the turfgrass. To express the gene properly in plants, its translation initiation codon was modified from GTG to ATG. A similar activity of C120 was obtained following the modification.

Amino Acid Sequence↗
PubMed2005

Genetic susceptibility of catechol-O-methyltransferase polymorphism in Japanese patients with breast cancer.

Polymorphic catechol-O-methyltransferase (COMT) catalyzes the O-methylation of catechol estrogens. It has been reported that COMT polymorphism is a representative genetic trait related to the susceptibility of an individual to breast cancer. However, there is no consensus concerning the association between breast cancer in Japanese patients and COMT polymorphism. To analyze the polymorphism distribution in Japanese patients with breast cancer, a molecular genotyping method using a polymerase chain reaction-based restriction fragment length polymorphism (PCR-RFLP) was used. Based on an analysis of 201 Japanese patients with breast cancer and 352 healthy control subjects, a significant difference was observed in either the distribution of genotypes (p=0.03) or allele frequencies between the two groups (p=0.01). The relative risk of breast cancer for genotypes (COMT(Met/Met) and COMT(Val/Met)) including the variant allele (COMT(Met)) was 1.47 compared to the wild allele (COMT(Val)) and homozygote (COMT(Val/Val)). Furthermore, the distribution of genotypes in post-menopausal patients with breast cancer showed a significant difference with that of healthy subjects of the same menopausal status (p=0.01). No significant difference was found between the distribution of genotypes and clinicopathological features of the cancer. These results suggest that COMT polymorphism may thus be implicated as a genetic trait affecting the susceptibility of an individual to breast cancer in a Japanese population and be an important genetic risk factor in the development of breast cancer in post-menopausal women.

Adult↗
PubMed2005

Adsorption of catechol from aqueous solution by aminated hypercrosslinked polymers.

Adsorption of catechol from aqueous solution with the hypercrosslinked polymeric adsorbent NDA-100 and its derivatives AH-1, AH-2 and AH-3 aminated by dimethylamine, the commercial resin Amberlite XAD-4 and weakly basic anion exchanger resin D301 was compared. It was found that the aminated hypercrosslinked resins had the highest adsorption capacities among the tested polymers. The empirical Freundlich equation was successfully employed to describe the adsorption process. Specific surface area and micropore structure of the adsorbent, in company with tertiary amino groups on matrix affected the adsorption performance towards catechol. In addition, thermodynamic study was carried out to interpret the adsorption mechanism. Kinetic study testified that the tertiary amino groups on the polymer matrix could decrease the adsorption rate and increase the adsorption apparent activation energy.

Adsorption↗
PubMed1990

Oxidation and DNA binding of (+)-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene in mouse epidermis in vivo and effects of coadministration of catechol.

Using a stereochemical probe as described by Marnett (Carcinogenesis (Lond.), 8: 1365-1373, 1987), we have investigated the mechanism of oxidation of (+)-[3H]BaP-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene [(+)-[3H]BaP-7,8-diol] in mouse epidermis in vivo. Groups of mice were topically treated with (+)-[3H]BaP-7,8-diol (60 nmol/mouse) and sacrificed at intervals from 1/2 to 8 h post treatment. (-)-Anti- and (+)-syn-7,8-[3H]dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (BPDE) were formed as metabolites in a ratio of about 4 to 1, respectively, as determined by HPLC analysis of the hydrolysis products. Pretreatment of mice with indomethacin, an inhibitor of prostaglandin H synthase, did not alter the ratio of anti- to syn-BPDE-derived hydrolysis products. Pretreatment of mice with the cytochrome P-450 inducer, beta-naphthoflavone, yielded twice the level of syn-[3H]BPDE in mouse skin at the 1/2-h survival point. However, this enhancing effect diminished over time. Coadministration of 1,2-dihydroxybenzene (catechol) with (+)-[3H]BaP-7,8-diol decreased the formation of (-)-anti-[3H]BPDE and also decreased lipid peroxidation, as measured by the extent of formation of thiobarbituric acid-reactive material in mouse epidermis. Analysis of mouse epidermal DNA adducts 24 h after topical application (+)-[3H]BaP-7,8-diol indicated that the major adduct is not formed from the major metabolite (-)-anti-BPDE. Acid hydrolysis of the major adduct resulted in the formation of a small amount of r-7,c-9,c-10,t-8-tetrahydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene and two unidentified products different from 7,8,9,10-tetrahydroxy-7,8,9,10-tetrahydro-BaP. Coadministered catechol suppressed the formation of this adduct by 30%. The present observation suggests that a peroxyl radical-mediated epoxidation pathway is involved in the oxidation of (+)-[3H]BaP-7,8-diol in mouse skin in vivo.

Animals↗
PubMed1989

[Screening of strains producing extracellular catechol 1,2-dioxygenase and fermentation conditions].

Two strains of Pseudomonus sp. having the extracellular catechol 1, 2-dioxygenase activity were selected from 112 bacterial strains. The conditions for enzyme production of the strains were examined. The optimal temperature and pH for enzyme formation were 30 degrees C and pH 6.8-7.0 respectively. Enzyme formation was enhanced by sodium benzoate, and was markedly inhibited by glucose, maltose and glycerol. Ammoniacal nitrogen sources were essential for cell growth and enzyme production. Sodium succinate was an effective inducer for enzyme formation. When the organism was grown in 0.15% sodium benzoate medium (pH 6.8-7.0) at 30 degrees C for 72 hours, about 10 units of catechol 1,2 dioxygenase per ml was obtained.

Catechol 1,2-Dioxygenase↗
PubMed1987

[Mechanism of the suppressive effect of catechol estrogen on the preovulatory LH surge].

The administration of 100 micrograms 2-hydroxyestrone (2-OHE1) or 2-hydroxyestradiol-17 beta (2-OHE2) at 0900h or 1000h in the morning of proestrus into normal 4-day cycling rats results in suppression of the preovulatory LH surge in the afternoon of that day. The LH-RH content of the median eminence in control rats decreases sharply in the afternoon from elevated noon levels. However, the catechol estrogen-treated rats do not show this decrease. These results indicate that the catecholestrogens block the preovulatory LH surge by preventing the release of LH-RH from the median eminence, but do not interfere with the synthesis and accumulation of LH-RH. Furthermore, injections of non-uterotropic 2-OHE1 twice at 30 minutes intervals into ovariectomized rats fail to affect the LH tonic secretion by 180 minutes after the initial injection. These data indicate that catechol estrogen interferes with the brief neuronal triggering phase necessary for LH-RH release, but does not affect the LH tonic secretion which is an estrogen-independent process.

Animals↗
PubMed1985

Effect of amphetamine on brain catecholamines, brain beta-endorphin, serum prolactin, catechol-O-methyltransferase and monoamine oxidase of various organs in the rat.

Rats were treated with amphetamine to induce an amphetamine psychosis which resembles paranoid schizophrenia. Brain catecholamines, brain beta-endorphin, serum prolactin as well as catechol-O-methyltransferase and monoamine oxidase were subsequently measured. The norepinephrine levels were significantly lower in brain regions of rats treated with amphetamine whereas levels of dopamine and beta-endorphin remained the same. No significant changes were found in the levels of catechol-O-methyltransferase, monoamine oxidase and serum prolactin. In view of recent findings by other investigators in this field, our results suggest an important role of the adrenergic system in the pathogenesis of amphetamine psychosis.

Amphetamine↗
PubMed1985

Catechol formation of fluoro- and bromo-substituted estradiols by hamster liver microsomes. Evidence for dehalogenation.

We have examined the validity of using fluorine-substituted estrogens as probes to assess the significance of 2- and 4-hydroxylation in estrogen-induced carcinogenesis in the hamster. Liver microsomes from castrated hamsters were incubated with 2-fluoro-, 4-fluoro-, or 2,4-difluoroestradiols and analogous bromo-substituted estradiols to determine the extent of 2- and 4-hydroxylation with these substrates. Estrogen 2- and 4-hydroxylase activity was determined by radioenzymatic assay, and the 3H-labeled monomethyl ether products were identified by high performance liquid chromatography. With unsubstituted 17 beta-estradiol as substrate, 97% of the product formed was 2-hydroxylated, and 3% was 4-hydroxylated. The monosubstituted fluoroestradiols exhibited more than a 2-fold enhanced ability to form catechol estrogens compared with their corresponding bromoestradiols. Data presented herein indicate substantial defluorination when 2-fluoroestradiol was the substrate, which amounted to 36% of the total product formed, and 32% of the rate of 2-hydroxylation found with unsubstituted 17 beta-estradiol as substrate. Interestingly, the rate of 4-hydroxylation was elevated 20- and 6.7-fold, respectively, when 2-fluoroestradiol and 2,4-difluoroestradiol were the substrates compared to the rate with 17 beta-estradiol. Moreover, both 4-fluoroestradiol and 2,4-difluoroestradiol exhibited at least a 1.6-fold greater rate of 2-hydroxylation compared with 17 beta-estradiol. In contrast, the rate of dehalogenation with 2-bromoestradiol was only 12% of that found with 2-fluoroestradiol. No debromination was obtained with 4-bromoestradiol, and essentially no catechols were formed using 2,4-dibromoestradiol as substrate with these hamster liver microsomes. These data clearly provide evidence for defluorination of these substituted estrogens, particularly at the C-2 position, and seriously hamper the use of fluoroestrogens in studies of hormonal carcinogenicity.

Animals↗
PubMed1986

Effect of continuous intraventricular estrogen or catechol estrogen treatment on catecholamine turnover in various brain regions.

The effect of 7-day i.v.t. administration of catechol estrogens (CE) or estrogens (5 micrograms/day) on the catecholamine turnover rate of various brain areas was examined in ovariectomized rats. Norepinephrine turnover was increased significantly in the hypothalamus and cerebral cortex by estradiol treatment but not by any CEs tested when compared to control values. However, the turnover rate of dopamine in the cerebral cortex was increased compared to control values only by the 2-hydroxyestrogens (2-hydroxyestradiol and 2-hydroxyestrone) and estradiol was without effect. Only estrogens and CEs with physiologically significant estrogen receptor binding affinities (17 beta-estradiol, moxestrol, 2-hydroxyestradiol and 4-hydroxyestradiol) decreased the turnover rate of dopamine in the corpus striatum compared to control values. Estrogens (17 alpha-estradiol and 2-hydroxyestrone) which are weak ligands for the estrogen receptor did not affect striatal dopamine turnover. In addition, body weight gain measured during estrogen treatment was reduced by CEs and estrogens which have significant estrogen receptor affinities. These results suggest that the CEs may play a role in central modulation of catecholaminergic function by estrogens either through direct actions of the catechol moiety or activation of estrogen receptors.

Animals↗
PubMed1987

Semiquinone anion radicals from addition of amino acids, peptides, and proteins to quinones derived from oxidation of catechols and catecholamines. An ESR spin stabilization study.

Either chemical or enzymatic oxidation of catechols or catecholamines in the presence of nucleophiles (amino acids, peptides, and proteins) leads to the production of ring-substituted o-semiquinones which have been detected by ESR spin stabilization techniques. In many cases, radicals have been completely characterized and structures assigned. Chemical considerations point to a mechanism involving addition of nucleophile to o-quinone, followed by oxidation of product to o-semiquinone. These results confirm that addition occurs in oxidizing polyhydroxy aromatic systems, probably via o-quinone, in a reaction considered to account for much of the toxicity found for catechols and catecholamines.

Amino Acids↗
PubMed1986

Formation of excited states during the oxidation of caffeic and 3,4 dihydroxyphenylacetic acids catalyzed by catechol oxidase.

The oxidation of caffeic and 3,4-dihydroxyphenylacetic acids by catechol oxidase leads to formation of excited species as indicated by chlorophyll sensitized emission. The chemiexcitation step and the transfer are efficient and favoured by the hydrophobic medium. The oxidation of Catecholamines such as L-DOPA, adrenaline and noradrenaline by catechol oxidase does not lead to excitation of chlorophyll.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Animal models of myoclonus using 1,2-dihydroxybenzene (catechol) and chloralose.

A description of the physiological effects and pharmacological actions of catechol (1,2-dihydroxybenzene) and chloralose (monoglucochloralose) on muscular activity in animals has been presented. Catechol produces a stimulus-sensitive state wherein a tactile stimulus to a limb evokes a jerk in the muscles of that limb. This jerk can consist of three components: a polysynaptic spinal reflex, a periphero-corticospinal reflex, and a brainstem reflex. Chloralose also produces a stimulus-sensitive state with two components: a polysynaptic spinal reflex in the stimulated limb and a presumed spino-bulbo-spinal reflex activation of all body flexor muscles. The relevance of these agents as animal models for the mechanism of generation of human myoclonic activity has been discussed.

Acetylcholine↗
PubMed1981

A study of tobacco carcinogenesis. XX. Role of catechol as a major cocarcinogen in the weakly acidic fraction of smoke condensate.

The weakly acidic fraction of cigarette smoke condensate was fractionated by preparative high-pressure liquid chromatography into major subfractions I-IV. Major subfractions II and III were fractionated further into subfractions A-J. Subfractions A-J were tested for cocarcinogenicity on the skin of noninbred Ha:ICR Swiss albino mice by application with 0.003% benzo[a]pyrene. Subfractions A-C and F-J showed significant cocarcinogenic activity; subfractions A, F, and H were the most active. Catechol was a major component of subfraction A and was also detected in subfractions B-D and F. Major components of the other subfractions included hydroquinone (B), coniferyl alcohol (C and H), hydroxyphenyl alcohols (D), alkyl-2-hydroxy-2-cyclopenten-1-ones (C, D, and F), hydroxyacetophenones (F), phenolic cyano compounds (F), and fatty acids (F). The results demonstrate the importance of catechol as a cocarcinogen in the weakly acidic fraction of cigarette smoke condensate and indicate the presence of other cocarcinogens.

Animals↗
PubMed1982

[Kinetics of the catalytic oxidation of catechol in aqueous solutions of ceruloplasmin in the presence of Fe3+].

The kinetics of oxidation of catechol in aqueous solutions containing ceruloplasmin and Fe3+, were studied. It was found that Fe3+ at low concentrations accelerate the reaction. The inhibiting effect of high concentrations of Fe3+ is due to the formation of catalytically inactive enzyme complexes with catechol oxidation products. A mechanism of this process is proposed.

Catechols↗
PubMed1981

Determination of the position of monooxygenation in the formation of catechol catalyzed by salicylate hydroxylase.

[3,5-2H]Salicylate was obtained by a hydrogen/deuterium exchange reaction carried out in 2H2O. Using this deuterated salicylate as a substrate for salicylate hydroxylase, the product catechol was isolated and characterized with respect to the positions of deuterium retention. Based on nuclear magnetic resonance and mass spectroscopy analyses, the product was identified as [3,5-2H]catechol. It is thus unequivocally demonstrated that salicylate is decarboxylated and hydroxylated at the same ring position. Also consistent with this conclusion is the lack of a kinetic isotope effect for the deuterated salicylate substrate.

Catechols↗
PubMed1994

Ethnic differences in erythrocyte catechol-O-methyltransferase activity in black and white Americans.

Catechol-O-methyltransferase (COMT) catalyzes the O-methylation of catecholamine and catechol drugs such as levodopa and methyldopa. Human COMT activity is inherited as an autosomal co-dominant trait; approximately 25% of white individuals have low activity consistent with homozygosity for a low activity allele, about 50% have intermediate activity (i.e., heterozygous genotype) and 25% have high activity. COMT activity has not been characterized in African-Americans or other black populations. To investigate potential ethnic and gender differences in COMT, we measured erythrocyte COMT activity in 195 unrelated black and 202 unrelated white healthy individuals living in the Southeast United States. Overall, the black population had significantly higher COMT activity than the white population (median 15.7 vs. 11.4 U/ml of packed red blood cell volume; P < .001). Maximum likelihood estimation of COMT activity distribution identified significant ethnic differences, with high activity in 23% of whites and 55% of blacks, intermediate activity in 50% of whites and 38% of blacks and low activity in 27% of whites and 7% of blacks. No greater differences in COMT activity were observed in either ethnic group. We conclude that red blood cell COMT activity is significantly higher in black subjects than white subjects. Hardy-Weinberg estimates indicate that this ethnic difference is due to a higher frequency of high activity COMT alleles in blacks vs. whites (0.74 vs. 0.48).

Adolescent↗