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PubMed2003

Electrochemical degradation of bromopyrogallol red in presence of cobalt ions.

This paper summarizes the results of a degradation test of bromopyrogallol red (BPR) and textile dye wastewater (TDW) with a conventional three-electrode potentiostatic system in the presence of cobalt ions (electro Co(2+)-H2O2 system). H2O2, produced by the two-electron reduction of O2 at the cathode, would react with Co2+ ions, leading to the generation of hydroxyl radicals (*OH), which caused the degradation of the organic pollutants. With BPR degradation process as the reference point, the optimal conditions (pH=4.0 and the concentration of Co2+ is 0.1 mM) and the treating capacity of the system were both studied and compared with electro-Fenton's reagent. Many benefits were shown by the electro Co(2+)-H2O2 system, such as less metal ions consumption, more moderate conditions and faster reaction process. Treated with the system for 0.5 h, chemical oxygen demand and biological oxygen demand of TDW (pH=5.2), without pH adjustment, were reduced by 95.7% and 92.7%, respectively. These characteristics make the method another appropriate solution for wastewater treatment, especially for those contaminated by organic pollutants.

Cobalt↗
PubMed1983

[Substrate specificity of phenoloxidase (EC 1.14.18.1)].

Using 10 microns thick cryostat-slides of spleen and gut from white rats the following substances (in 2 different concentrations) were tested as substrates for the enzyme phenoloxidase compared with dihydroxyphenylalanine: pyrogallic acid, resorcin, 2.4-dinitrophenol, tyraminhydrochloride, o-cresol, and epinephrine. Only pyrogallic acid and resorcin resulted in positive reaction. Resorcin showed a positive reaction only when the higher concentration is employed. The investigations show clearly that the detectable enzyme in gut, spleen, and oral cavity is a polyphenoloxidase, which occurs consequently not only in granulocytes.

Animals↗
PubMed1997

Scanning tunnelling microscopy observation of cytochrome-c denaturation induced by bromopyrogal red on highly oriented pyrolytic graphite.

The denaturation of cytochrome-c (cyt-c) induced by bromopyrogal red (BPR) was studied by scanning tunnelling microscopy (STM) on the electrochemically pretreated highly oriented pyrolytic graphite (HOPG) surface. STM images reveal that denatured cyt-c molecules exist in variable states including aggregates, globular compact, partially unfolded and combined with BPR molecule. The apparently low image contrast of denatured cyt-c observed in this experiment comparing to that of native cyt-c molecules, and the relative low image contrast of the unfolded part comparing with the compact globular part, are ascribed to the unfavourable tunnelling paths for the conformational variations of denatured cyt-c molecules.

Animals↗
PubMed2000

Laccase activity tests and laccase inhibitors.

Sulfhydryl organic compounds described as laccase inhibitors: dithiothreitol, thioglycolic acid, cysteine, diethyldithiocarbamic acid, and sodium azide were tested for their activity toward laccase of Trametes versicolor in different test systems utilising 2, 2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and 2, 6-dimethoxyphenol as enzyme substrates. Only sodium azide acted as a true laccase inhibitor and showed no significant interference with the enzyme tests. All other substances did not significantly inhibit the laccase activity and the previously reported inhibitory effects result from the reductions of the reaction products such as ABTS radical cation and diquinone or subsequent non-enzymatic interactions during substrate oxidation. The latter apparently forms a complex with unreacted ABTS displaying varied spectral characteristics and resulting in an underestimation of enzyme activity.

Benzothiazoles↗
PubMed1990

Acute toxicity testing in the nonlethal dose range: a new approach.

A new modification of acute toxicity testing of chemicals in rats is presented. Instead of using death as the principal criterion of toxicity, it is based on a careful, standardized clinical assessment of toxic signs measured in the nonlethal dose range. Test compounds are administered to groups of rats at four dose levels, selected on the basis of pilot experiments. General indices of toxicity, i.e., body weight gain, food and water consumption, and body temperature, are recorded at regular intervals; activity in the home cage is monitored continuously with a newly developed passive infrared device; neurobehavioral dysfunctions are assessed repeatedly with a checklist; and routine hematology is done on the 4th day after administration of the test compounds. All measured signs of toxicity are scored in relation to the control groups so that the absolute magnitude of the score increases as a function of the deviation from the normal conditions of the animals. In order to take into consideration the course of intoxication and the rate of recovery, toxicity scores are added over the duration of the whole experiment. For each variable measured, the resulting total scores are converted into a relative point system, scaling from 0 to 10 points. These points are added to a single "total ToxScore" value for each dose group. A regression line is calculated for these total ToxScore points, and the dose giving 15 total ToxScore points is determined. Based on the results obtained with nine reference substances, a classification system is proposed that is comparable to that based on LD50 values. It is concluded that the proposed test procedure provides much more information on the signs of acute toxicity, the course of the intoxication, the slope of the dose-effect curve, and the rate of recovery than does the standard LD50 test. In addition, the degree of distress and suffering of the animals is reduced.

Acetanilides↗
PubMed2003

Roles of human liver cytochrome P450 3A4 and 1A2 enzymes in the oxidation of myristicin.

The aim of this work was to identify the form(s) of human liver cytochrome P450 (CYP) involved in the hepatic transformation of myristicin to its major metabolite, 5-allyl-1-methoxy-2,3-dihydroxybenzene. When microsomes prepared from different human liver samples were compared, the activity of 5-allyl-1-methoxy-2,3-dihydroxybenzene formation was well correlated (r(2)=0.87) with nifedipine oxidation (a marker of CYP3A4). With a microsomal sample having high CYP3A4 activity, microsomal oxidation of myristicin to the major metabolite (5-allyl-1-methoxy-2,3-dihydroxybenzene) was markedly inhibited by gestodene and ketoconazole, selective inhibitors of CYP3A enzymes, but not by any of several other P450 inhibitors. Antibodies raised against CYPs 3A4 and 1A2 could also inhibit the oxidation of myristicin, but antibodies recognizing other CYPs had no effect. The oxidation of myristicin to 5-allyl-1-methoxy-2,3-dihydroxybenzene was catalyzed by purified bacterial recombinant CYPs 3A4 and 1A2. These results provide evidence that CYP3A4 (and possibly other CYP3A enzymes) and CYP1A2 play roles in the formation of the major metabolite, 5-allyl-1-methoxy-2,3-dihydroxybenzene.

Alkenes↗
PubMed1998

In vitro and in vivo metabolism of myristicin in the rat.

Myristicin [5-allyl-1-methoxy-2,3-(methylenedioxy)benzene] is a flavoring plant constituent and has been known to produce significant psychopharmacological responses as well as insecticidal activity. From in vitro and in vivo metabolism of myristicin, the two metabolites 5-allyl-1-methoxy-2,3-dihydroxybenzene and 1'-hydroxymyristicin were identified using GC-MS after derivatization of sample matrices with a mixture of BSTFA-TMCS. Those metabolites from in vitro study were also confirmed in urine after an oral administration of myrisitcin to rats, and enzymatic hydrolysis of urine suggested that these metabolites were excreted as conjugated forms as well.

Allylbenzene Derivatives↗
PubMed2001

Nutmeg (myristicin) poisoning--report on a fatal case and a series of cases recorded by a poison information centre.

In literature, cases of nutmeg abuse have been described repeatedly, but only one fatal case of poisoning was reported [1]. In the present case, myristicin (4 microg/ml) was detected for the first time in the postmortal serum of a 55-year-old woman. Identification was achieved with the aid of UV-VIS spectroscopy and TLC; for quantification, HPLC was used. Because also flunitrazepam (0.072 microg/ml) was found, death had probably been due to the combined toxic effect of both substances. From 1996 to 1998, in a series of cases, seven poisonings with nutmeg were recorded by the Erfurt Poison Information Centre. Even where higher doses (20-80 g of powder) had been ingested, a life-threatening situation was never observed. In one of these cases, a myristicin blood level of 2 microg/ml was measured 8h after ingestion of two to three tablespoonful of nutmeg powder (approx. 14-21 g, or 280-420 mg/kg).

Adolescent↗
PubMed1987

Homogentisic acid autoxidation and oxygen radical generation: implications for the etiology of alkaptonuric arthritis.

The metabolic disorder, alkaptonuria, is distinguished by elevated serum levels of 2,5-dihydroxyphenylacetic acid (homogentisic acid), pigmentation of cartilage and connective tissue and, ultimately, the development of inflammatory arthritis. Oxygen radical generation during homogentisic acid autoxidation was characterized in vitro to assess the likelihood that oxygen radicals act as molecular agents of alkaptonuric arthritis in vivo. For homogentisic acid autoxidized at physiological pH and above, yielding superoxide (O2-)2 and hydrogen peroxide (H2O2), the homogentisic acid autoxidation rate was oxygen dependent, proportional to homogentisic acid concentration, temperature dependent and pH dependent. Formation of the oxidized product, benzoquinoneacetic acid was inhibited by the reducing agents, NADH, reduced glutathione, and ascorbic acid and accelerated by SOD and manganese-pyrophosphate. Manganese stimulated autoxidation was suppressed by diethylenetriaminepentaacetic acid (DTPA). Homogentisic acid autoxidation stimulated a rapid cooxidation of ascorbic acid at pH 7.45. Hydrogen peroxide was among the products of cooxidation. The combination of homogentisic acid and Fe3+-EDTA stimulated hydroxyl radical (OH.) formation estimated by salicylate hydroxylation. Ferric iron was required for the reaction and Fe3+-EDTA was a better catalyst than either free Fe3+ or Fe3+-DTPA. SOD accelerated OH. production by homogentisic acid as did H2O2, and catalase reversed much of the stimulation by SOD. Catalase alone, and the hydroxyl radical scavengers, thiourea and sodium formate, suppressed salicylate hydroxylation. Homogentisic acid and Fe3+-EDTA also stimulated the degradation of hyaluronic acid, the chief viscous element of synovial fluid. Hyaluronic acid depolymerization was time dependent and proportional to the homogentisic acid concentration up to 100 microM. The level of degradation observed was comparable to that obtained with ascorbic acid at equivalent concentrations. The hydroxyl radical was an active intermediate in depolymerization. Thus, catalase and the hydroxyl radical scavengers, thiourea and dimethyl sulfoxide, almost completely suppressed the depolymerization reaction. The ability of homogentisic acid to generate O2-, H2O2 and OH. through autoxidation and the degradation of hyaluronic acid by homogentisic acid-mediated by OH. production suggests that oxygen radicals play a significant role in the etiology of alkaptonuric arthritis.

Alkaptonuria↗
PubMed2003

Simultaneous determination of 2-methoxyphenol, 2-methoxy-4-methylphenol, 2,6-dimethoxyphenol and 4'-hydroxy-3'-methoxyacetophenone in urine by capillary gas chromatography.

A method for the simultaneous determination of 2-methoxyphenol, 2-methoxy-4-methylphenol, 2,6-dimethoxyphenol and 4'-hydroxy-3'-methoxyacetophenone in urine has been described. The metabolites were analyzed after enzymatic hydrolysis and extraction on octyl (C8) cartridges by using gas chromatography with flame ionization detection and a 5/95% copolymer of diphenyl-poly(dimethylsiloxane) capillary column. Methoxyphenols were well separated within 12 min. Recovery was over 90% in the range from 0.5 to 20 microg/ml; the detection limit was varying in the range of 0.05-0.11 microg/ml. The relative standard deviations and the accuracy were in the range of 3.1-15.5 and 2.4-16.0%, respectively.

Acetophenones↗
PubMed1994

Mechanism of manganese peroxidase compound II reduction. Effect of organic acid chelators and pH.

The effect of oxalate, malonate, lactate, and succinate chelators on the reduction of Phanerochaete chrysosporium manganese peroxidase compound II by MnII was investigated using stopped-flow techniques. All rate data were collected from single-turnover experiments under pseudo-first-order conditions. With oxalate, the reduction of compound II by MnII exhibited saturation behavior when the observed pseudo-first-order rate constants were plotted against oxalate concentration. The plots passed through the origin, indicating that the reduction by MnII is irreversible at all concentrations of oxalate. Maximal stimulation of the rate of compound II reduction occurred at 2 mM oxalate, the concentration of oxalate found in the extracellular medium of agitated cultures of this fungus. In contrast, maximal stimulation of the reduction of compound II by MnII only was observed at high (> 20 mM) nonphysiological concentrations of malonate and lactate. Furthermore, at low concentrations of malonate and lactate, the reduction of compound II appeared to be reversible. These results suggest that at physiological concentrations oxalate chelates and stabilizes MnIII, enhancing its efficient removal from the enzyme. The rate constants for compound II reduction exhibited bell-shaped curves as a function of pH and had optima at pHs 5.0-5.4. In the presence of succinate, triphasic kinetics were observed for compound II reduction by MnII. In contrast to the reduction of compound II by MnII, various chelators had no observable effect on the formation of compound I. However, they did affect the steady-state oxidation of 2,6-dimethoxyphenol.

Basidiomycota↗
PubMed1999

Arginine 177 is involved in Mn(II) binding by manganese peroxidase.

Site-directed mutations R177A and R177K in the gene encoding manganese peroxidase isozyme 1 (mnp1) from Phanerochaete chrysosporium were generated. The mutant enzymes were expressed in P. chrysosporium during primary metabolic growth under the control of the glyceraldehyde-3-phosphate dehydrogenase gene promoter, purified to homogeneity, and characterized by spectroscopic and kinetic methods. The UV-vis spectra of the ferric and oxidized states and resonance Raman spectra of the ferric state were similar to those of the wild-type enzyme, indicating that the heme environment was not significantly affected by the mutations at Arg177. Apparent K(m) values for Mn(II) were approximately 20-fold greater for the R177A and R177K MnPs than for wild-type MnP. However, the apparent K(m) values for the substrates, H(2)O(2) and ferrocyanide, and the k(cat) values for Mn(II) and ferrocyanide oxidation were similar to those of the wild-type enzyme. The second-order rate constants for compound I (MnPI) reduction of the mutant MnPs by Mn(II) were approximately 10-fold lower than for wild-type MnP. In addition, the K(D) values calculated from the first-order plots of MnP compound II (MnPII) reduction by Mn(II) for the mutant enzymes were approximately 22-fold greater than for wild-type MnP. In contrast, the first-order rate constants for MnPII reduction by Mn(II) were similar for the mutant and wild-type MnPs. Furthermore, second-order rate constants for the wild-type and mutant enzymes for MnPI formation, for MnPI reduction by bromide, and for MnPI and MnPII reduction by ferrocyanide were not significantly changed. These results indicate that both the R177A and R177K mutations specifically affect the binding of Mn, whereas the rate of electron transfer from Mn(II) to the oxidized heme apparently is not affected.

Amino Acid Substitution↗
PubMedDate not supplied

Block copolymer microdomains: a novel medium for enzymatic reactions.

Block copolymers exhibit the phenomenon of microdomain formation in pure states as well as in solutions. The microdomains vest the block copolymer assemblies with the intriguing characteristics of microheterogeneous media. We demonstrate that this microheterogeneity in hydrophobic-hydrophilic block copolymer systems can be exploited for immobilizing enzymes and to carry out enzymatic reactions. Examples involving cholesterol oxidase and horseradish peroxidase are provided here. The observed changes in the enzymatic activity in block copolymer microdomains from that in the aqueous media are interpreted in terms of the hydrophobicity of the reaction microenvironment. The block copolymer microdomains are simple to generate, well defined, and easily reproducible. Therefore, they hold significant potential as media for enzymatic biosynthetic reactions when the substrates or the reaction products are water insoluble.

Benzocycloheptenes↗
PubMedDate not supplied

Degradation of water-insoluble dyes by microperoxidase-11, an effective and stable peroxidative catalyst in hydrophilic organic media.

Microperoxidase-11 (MP-11), a heme-containing undecapeptide, derived from horse heart cytochrome c was utilized as a peroxidative catalyst. Catalytic characteristics of MP-11 in hydrophilic organic media were studied using 2,6-dimethoxyphenol as a reducing substrate in a series of organic solvents at various concentrations, indicating that MP-11 was active in water-miscible organic solvents but at least 5% water was compulsory for the catalytic action. Thus, MP-11 was not active in hydrophobic solvents. The pH of the water portion in the media affected the reaction rate. The optimal pH was found to be 9, where a release of protons from either an oxidizing or reducing substrate to the media was facilitated. The decolorization of water-insoluble synthetic dyes by MP-11 in 90% methanol was attempted. MP-11 showed effective decolorization activities against either azo or anthraquinone dyes. The degradation pathway for Solvent Orange 7 was investigated in detail, showing that MP-11 catalyzed the oxidative cleavage of the azo linkage to generate 1,2-naphthoquinone and 2,4-dimethylphenol as key intermediates.

Animals↗