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PubMed1995

Close Correlation between Heat Shock Response and Cytotoxicity in Neurospora crassa Treated with Aliphatic Alcohols and Phenols.

In Neurospora crassa the aliphatic alcohols methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, ethylene glycol, glycerol, and allyl alcohol and the phenolic compounds phenol, hydroquinone, resorcinol, pyrogallol, phloroglucinol, sodium salicylate, and acetylsalicylic acid were analyzed with respect to their capacities to induce heat shock proteins (HSP) and to inhibit protein synthesis. Both the alcohols and phenols showed the greatest levels of HSP induction at concentrations which inhibited the overall protein synthesis by about 50%. The abilities of the different alcohols to induce the heat shock response are proportional to their lipophilicities: the lipophilic alcohol isobutanol is maximally inductive at about 0.6 M, whereas the least lipophilic alcohol, methanol, causes maximal induction at 5.7 M. The phenols, in general, show a higher capability to induce the heat shock response. The concentrations for maximal induction range between 25 mM (sodium salicylate) and 100 mM (resorcinol). Glycerol (4.1 M) shifted the concentration necessary for maximal HSP induction by hydroquinone from 50 to 200 mM. The results reveal that the induction of HSP occurs under conditions which considerably constrain cell metabolism. The heat shock response, therefore, does not represent a sensitive marker for toxicity tests but provides a good estimate for the extent of cell damage.

Journal Article↗
PubMed1995

Isolation and characterization of an anaerobic ruminal bacterium capable of degrading hydrolyzable tannins.

An anaerobic diplococcoid bacterium able to degrade hydrolyzable tannins was isolated from the ruminal fluid of a goat fed desmodium (Desmodium ovalifolium), a tropical legume which contains levels as high as 17% condensed tannins. This strain grew under anaerobic conditions in the presence of up to 30 g of tannic acid per liter and tolerated a range of phenolic monomers, including gallic, ferulic, and p-coumaric acids. The predominant fermentation product from tannic acid breakdown was pyrogallol, as detected by high-performance liquid chromatography and mass spectrometry. Tannic acid degradation was dependent on the presence of a sugar such as glucose, fructose, arabinose, sucrose, galactose, cellobiose, or soluble starch as an added carbon and energy source. The strain also demonstrated resistance to condensed tannins up to a level of 4 g/liter.

Animals↗
PubMed1998

Purification and characterization of gallic acid decarboxylase from pantoea agglomerans T71

Oxygen-sensitive gallic acid decarboxylase from Pantoea (formerly Enterobacter) agglomerans T71 was purified from a cell extract after stabilization by reducing agents. This enzyme has a molecular mass of approximately 320 kDa and consists of six identical subunits. It is highly specific for gallic acid. Gallic acid decarboxylase is unique among similar decarboxylases in that it requires iron as a cofactor, as shown by plasma emission spectroscopy (which revealed an iron content of 0.8 mol per mol of enzyme subunit), spectrophotometric analysis (absorption shoulders at 398 and 472 nm), and inhibition of the enzyme activity by 2,2'-bipyridyl, o-phenanthroline, and EDTA. Another interesting feature of this strain is the fact that it contains a tannase, which is used together with the gallic acid decarboxylase in a two-enzyme resting cell bioconversion to synthesize valuable pyrogallol from readily available tannic acid.

Journal Article↗
PubMed1999

Purification and characterization of a secreted laccase of Gaeumannomyces graminis var. tritici.

We purified a secreted fungal laccase from filtrates of Gaeumannomyces graminis var. tritici cultures induced with copper and xylidine. The active protein had an apparent molecular mass of 190 kDa and yielded subunits with molecular masses of 60 kDa when denatured and deglycosylated. This laccase had a pI of 5.6 and an optimal pH of 4.5 with 2,6-dimethoxyphenol as its substrate. Like other, previously purified laccases, this one contained several copper atoms in each subunit, as determined by inductively coupled plasma spectroscopy. The active enzyme catalyzed the oxidation of 2, 6-dimethoxyphenol (Km = 2.6 x 10(-5) +/- 7 x 10(-6) M), catechol (Km = 2.5 x 10(-4) +/- 1 x 10(-5) M), pyrogallol (Km = 3.1 x 10(-4) +/- 4 x 10(-5) M), and guaiacol (Km = 5.1 x 10(-4) +/- 2 x 10(-5) M). In addition, the laccase catalyzed the polymerization of 1, 8-dihydroxynaphthalene, a natural fungal melanin precursor, into a high-molecular-weight melanin and catalyzed the oxidation, or decolorization, of the dye poly B-411, a lignin-like polymer. These findings indicate that this laccase may be involved in melanin polymerization in this phytopathogen's hyphae and/or in lignin depolymerization in its infected plant host.

Ascomycota↗
PubMed2005

The Brucella abortus Cu,Zn superoxide dismutase is required for optimal resistance to oxidative killing by murine macrophages and wild-type virulence in experimentally infected mice.

Two-dimensional gel electrophoretic analysis of cell lysates from Brucella abortus 2308 and the isogenic hfq mutant Hfq3 revealed that the RNA binding protein Hfq (also known as host factor I or HF-I) is required for the optimal stationary phase production of the periplasmic Cu,Zn superoxide dismutase SodC. An isogenic sodC mutant, designated MEK2, was constructed from B. abortus 2308 by gene replacement, and the sodC mutant exhibited much greater susceptibility to killing by O(2)(-) generated by pyrogallol and the xanthine oxidase reaction than the parental 2308 strain supporting a role for SodC in protecting this bacterium from O(2)(-) of exogenous origin. The B. abortus sodC mutant was also found to be much more sensitive to killing by cultured resident peritoneal macrophages from C57BL6J mice than 2308, and the attenuation displayed by MEK2 in cultured murine macrophages was enhanced when these phagocytes were treated with gamma interferon (IFN-gamma). The attenuation displayed by the B. abortus sodC mutant in both resting and IFN-gamma-activated macrophages was alleviated, however, when these host cells were treated with the NADPH oxidase inhibitor apocynin. Consistent with its increased susceptibility to killing by cultured murine macrophages, the B. abortus sodC mutant also displayed significant attenuation in experimentally infected C57BL6J mice compared to the parental strain. These experimental findings indicate that SodC protects B. abortus 2308 from the respiratory burst of host macrophages. They also suggest that reduced SodC levels may contribute to the attenuation displayed by the B. abortus hfq mutant Hfq3 in the mouse model.

Animals↗
PubMed1972

Electron transport systems of Nitrosomonas: isolation of a membrane-envelope fraction.

Freezing and thawing of Nitrosomonas, followed by centrifugation of the homogenate at 3,000 x g, resulted in a fraction which appeared to consist of an intact membrane-envelope complex and contained approximately 50% of the cell protein and more than 90% of the ubiquinone and cytochrome A-type mammalian cytochrome c oxidase activity. The supernatant fraction, resulting from subsequent centrifugation of the extract at 100,000 x g, contained approximately 50% of the cell protein and more than 80% of the B- and C-type cytochrome and P-463 and the enzymes glutamate dehydrogenase; hydroxylamine dehydrogenase; nitrite synthetase; nitrite reductase; and 2,6-dichlorophenolindophenol-, p-phenylenediamine-, pyrogallol-, and hydroquinone-oxidase. Data on the concentration of electron transport components in Nitrosomonas are presented.

Bacterial Proteins↗
PubMed1984

Properties of salicylate hydroxylase and hydroxyquinol 1,2-dioxygenase purified from Trichosporon cutaneum.

Salicylate hydroxylase (salicylate 1-monooxygenase, EC 1.14.13.1) was purified from the soil yeast Trichosporon cutaneum. The enzyme contained flavin adenine dinucleotide and was monomeric, with a molecular weight of 45,300. In addition to salicylate, the four isomeric dihydroxybenzoates having one hydroxyl adjacent to carboxyl in the benzene nucleus were oxidatively decarboxylated without formation of hydrogen peroxide. One of these isomers, gentisate, was rapidly oxidized to hydroxyquinol by the enzyme but did not serve as an effective single carbon source for T. cutaneum; however, when growing with salicylate, cells also readily utilized gentisate for growth. Hydroxyquinol 1,2-dioxygenase (EC 1.13.11....) is a newly investigated enzyme which was purified from T. cutaneum grown with 4-hydroxybenzoate. The enzyme was red, contained ferric iron, and was specific for hydroxyquinol; catechol and pyrogallol were oxidized at less than 1% of the rate for hydroxyquinol, and no activity could be detected against seven other catechols. The enzyme was composed of two nonidentical subunits having molecular weights of 39,600 and 38,200 and was apparently dimeric.

Dioxygenases↗
PubMed1995

Purification and characterization of 6-chlorohydroxyquinol 1,2-dioxygenase from Streptomyces rochei 303: comparison with an analogous enzyme from Azotobacter sp. strain GP1.

The enzyme which cleaves the benzene ring of 6-chlorohydroxyquinol was purified to apparent homogeneity from an extract of 2,4,6-trichlorophenol-grown cells of Streptomyces rochei 303. Like the analogous enzyme from Azotobacter sp. strain GP1, it exhibited a highly restricted substrate specificity and was able to cleave only 6-chlorohydroxyquinol and hydroxyquinol and not catechol, chlorinated catechols, or pyrogallol. No extradiol-cleaving activity was observed. In contrast to 6-chlorohydroxyquinol 1,2-dioxygenase from Azotobacter sp. strain GP1, the S. rochei enzyme had a distinct preference for 6-chlorohydroxyquinol over hydroxyquinol (kcat/Km = 1.2 and 0.57 s-1.microM-1, respectively). The enzyme from S. rochei appears to be a dimer of two identical 31-kDa subunits. It is a colored protein and was found to contain 1 mol of iron per mol of enzyme. The NH2-terminal amino acid sequences of 6-chlorohydroxyquinol 1,2-dioxygenase from S. rochei 303 and from Azotobacter sp. strain GP1 showed a high degree of similarity.

Amino Acid Sequence↗
PubMed1995

Biochemical and genetic analyses of a catalase from the anaerobic bacterium Bacteroides fragilis.

A single catalase enzyme was produced by the anaerobic bacterium Bacteroides fragilis when cultures at late log phase were shifted to aerobic conditions. In anaerobic conditions, catalase activity was detected in stationary-phase cultures, indicating that not only oxygen exposure but also starvation may affect the production of this antioxidant enzyme. The purified enzyme showed a peroxidatic activity when pyrogallol was used as an electron donor. It is a hemoprotein containing one heme molecule per holomer and has an estimated molecular weight of 124,000 to 130,000. The catalase gene was cloned by screening a B. fragilis library for complementation of catalase activity in an Escherichia coli catalase mutant (katE katG) strain. The cloned gene, designated katB, encoded a catalase enzyme with electrophoretic mobility identical to that of the purified protein from the B. fragilis parental strain. The nucleotide sequence of katB revealed a 1,461-bp open reading frame for a protein with 486 amino acids and a predicted molecular weight of 55,905. This result was very close to the 60,000 Da determined by denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified catalase and indicates that the native enzyme is composed of two identical subunits. The N-terminal amino acid sequence of the purified catalase obtained by Edman degradation confirmed that it is a product of katB. The amino acid sequence of KatB showed high similarity to Haemophilus influenzae HktE (71.6% identity, 66% nucleotide identity), as well as to gram-positive bacterial and mammalian catalases. No similarities to bacterial catalase-peroxidase-type enzymes were found. The active-site residues, proximal and distal hemebinding ligands, and NADPH-binding residues of the bovine liver catalase-type enzyme were highly conserved in B. fragilis KatB.

Amino Acid Sequence↗
PubMed1967

Enzymatic oxidation of tetramethyl-p-phenylenediamine and p-phenylenediamine by the electron transport particulate fraction of Azotobacter vinelandii.

The ability of the electron transport particulate fraction of Azotobacter vinelandii strain O to oxidize tetramethyl-p-phenylenediamine (TMPD) and p-phenylenediamine (PPD) was examined in detail. The highest specific activity for TMPD and PPD oxidation concentrated in the A. vinelandii O R(3) fraction. The A. vinelandii O R(3) fraction was used to develop a standard manometric assay which gave optimal oxidation rates for both of these dyes. The conditions of the assay and all essential related enzymatic kinetic parameters are presented. Other para derivatives of phenylenediamines also were oxidized readily, whereas ortho and meta derivatives were not. Hydroquinone, p-hydroxybenzoic acid, p-cresol, tyrosine, pyrogallol, pyrocatechol, and diphenylamine were not able to serve as electron donors for the A. vinelandii O R(3) system. The probable involvement of a particle-bound cytochrome oxidase is indicated by the marked sensitivity of both TMPD and PPD oxidation to cyanide, axide, phenylhydrazine, hydroxylamine, and, to a lesser degree, carbon monoxide.

Aniline Compounds↗
PubMed1968

Purification and properties of peroxidase from Nitrosomonas europaea.

Peroxidase from the obligate chemosynthetic bacterium Nitrosomonas europaea was purified 1,500-fold, and its properties were examined. The enzyme had a molecular weight of 53,000 and exhibited characteristic absorption maxima at 410, 524, and 558 mmu. The optimal pH and temperature were 7.5 and 44 C, respectively. The peroxidase reaction had an energy of activation of 5,850 cal/mole and required a primary substrate (H(2)O(2)) concentration of 7 x 10(-6)m to proceed at half maximal velocity (K(m)). Reduced cytochrome, c,p-phenylenediamine and pyrogallol acted as hydrogen donors to the purified peroxidase-H(2)O(2) complex. Conditions most suitable for the chemical oxidation of ammonium by H(2)O(2) were determined. The reaction was rapid and produced nitrite but no nitrate. Hydroxylamine was not detected as an intermediate, but it could substitute for ammonium in the system. Neither the rate nor the extent of these reactions was influenced by purified peroxidase, and no evidence was obtained to support a conclusion that the enzyme performs a vital role in the transformation of ammonium to nitrite by N. europaea.

Chemistry Techniques, Analytical↗
PubMed1981

Ketamine potentiates catecholamine responses of vascular smooth muscle by inhibition of extraneuronal uptake.

Effects of ketamine on responses to sympathomimetic amines were studied using isolated aortic and pulmonary artery strips from the rabbit. Ketamine (1.1 x 10(-5) to 3.7 x 10(-4) M) potentiated adrenaline-contracted strips. Potentiation was not impaired in tissues from animals pretreated with reserpine, with 6-hydroxydopamine, or its tissues pretreated with cocaine. Pretreatment of the strips with the catechol O-methyltransferase (COMT) inhibitors tropolone or pyrogallol or the inhibitor of extraneuronal uptake 17 beta-estradiol blocked the potentiation by ketamine; in addition, potentiation by the COMT and extraneuronal uptake inhibitors was abolished or greatly reduced by ketamine. In rabbit aorta, ketamine potentiated responses to the catecholamines (adrenaline greater than nordefrine greater than noradrenaline) but not to the noncatecholamines phenylephrine, methoxamine, and synephrine; instead a slight relaxant effect was observed. Ketamine potentiated, whereas cocaine inhibited, responses to tyramine Experiments using the technique of oil immersion demonstrated that ketamine reduced the rate at which aortic strips inactivate adrenaline even when monoamine oxidase (MAO) and neuronal uptake processes were fully inhibited. Uptake studies showed that ketamine and 17 beta-estradiol reduced extraneuronal accumulation of [3H]adrenaline in aortic strips. We conclude that ketamine is an inhibitor of extraneuronal uptake in the vascular smooth muscles studied and the importance of this mechanism in producing its known cardiovascular effect is discussed.

Animals↗
PubMed1993

Antihepatotoxic activity of phenolic flavan-3-ols and their derivatives.

The protective activity against carbon tetrachloride induced hepatotoxicity of several phenolic flavan-3-ols and their derivatives has been assessed. Our research showed that monomers possessing a pyrogallol moiety as the B-ring had greater activity and this was not directly related to the stereo-chemistry of the hydroxyl group at C-3 in the flavan unit. However, when a galloyl group was linked to the hydroxyl group to form a gallate, this product exhibited markedly more activity than other analogs. These results suggest that the antihepatotoxic activity of phenolic flavan-3-ols and their derivatives seem to be related to the galloylation at the C-3 hydroxyl group in the flavan skeleton rather than the structure of another moiety or the degree of condensation.

Animals↗
PubMed2001

Impairment of endothelial nitric oxide production by acute glucose overload.

We examined the effects of acute glucose overload (pretreatment for 3 h with 23 mM D-glucose) on the cellular productivity of nitric oxide (NO) in bovine aortic endothelial cells (BAEC). We had previously reported (Kimura C, Oike M, and Ito Y. Circ Res, 82: 677-685, 1998) that glucose overload impairs Ca(2+) mobilization due to an accumulation of superoxide anions (O(2)(-)) in BAEC. In control cells, ATP induced an increase in NO production, assessed by diaminofluorescein 2 (DAF-2), an NO-sensitive fluorescent dye, mainly due to Ca(2+) entry. In contrast, ATP-induced increase in DAF-2 fluorescence was impaired by glucose overload, which was restored by superoxide dismutase, but not by catalase or deferoxamine. Furthermore, pyrogallol, an O(2)(-) donor, also attenuated ATP-induced increase in DAF-2 fluorescence. In contrast, a nonspecific intracellular Ca(2+) concentration increase induced by the Ca(2+) ionophore A-23187, which depletes the intracellular store sites, elevated DAF-2 fluorescence in both control and high D-glucose-treated cells in Ca(2+)-free solution. These results indicate that glucose overload impairs NO production by the O(2)(-)-mediated attenuation of Ca(2+) entry.

Adenosine Triphosphate↗
PubMed2000

SOD-1 expression in pig coronary arterioles is increased by exercise training.

Coronary arterioles of exercise-trained (EX) pigs have enhanced nitric oxide (NO.)-dependent dilation. Evidence suggests that the biological half-life of NO. depends in part on the management of the superoxide anion. The purpose of this study was to test the hypothesis that expression of cytosolic copper/zinc-dependent superoxide dismutase (SOD)-1 is increased in coronary arterioles as a result of exercise training. Male Yucatan pigs either remained sedentary (SED, n = 4) or were EX (n = 4) on a motorized treadmill for 16-20 wk. Individual coronary arterioles ( approximately 100-microm unpressurized internal diameter) were dissected and frozen. Coronary arteriole SOD-1 protein (via immunoblots) increased as a result of exercise training (2.16 +/- 0.35 times SED levels) as did SOD-1 enzyme activity (measured via inhibition of pyrogallol autooxidation; approximately 75% increase vs. SED). In addition, SOD-1 mRNA levels (measured via RT-PCR) were higher in EX arterioles (1.68 +/- 0.16 times the SED levels). There were no effects of exercise training on the levels of SOD-2 (mitochondrial), catalase, or p67(phox) proteins. Thus chronic aerobic exercise training selectively increases the levels of SOD-1 mRNA, protein, and enzymatic activity in porcine coronary arterioles. Increased SOD-1 could contribute to the enhanced NO.-dependent dilation previously observed in EX porcine coronary arterioles by improving management of superoxide in the vascular cell environment, thus prolonging the biological half-life of NO.

Animals↗
PubMed1999

Superoxide anion impairs Ca(2+) mobilization in cultured human nasal epithelial cells.

We examined the effects of superoxide anion (O(-2)) on the intracellular Ca(2+) concentration in cultured human nasal epithelial cells. The cells were exposed to O(-2) by pretreatment with xanthine (X) and xanthine oxidase (XO); control cells were treated with X alone. When Ca(2+)-containing Krebs solution was reperfused in the thapsigargin-treated, store-depleted cells, reapplication-induced intracellular Ca(2+) concentration elevation was significantly smaller in X/XO-treated cells than in the control cells, suggesting that O(-2) impairs Ca(2+) release-activated Ca(2+) entry (CRAC). Bath application of ATP induced a steep Ca(2+) transient in both control and X/XO-treated cells. However, the concentration-response curve of the ATP-induced Ca(2+) transient was shifted to a higher concentration in X/XO-treated cells. The impairments of CRAC and ATP-induced Ca(2+) transient induced by X/XO were reversed by superoxide dismutase. Furthermore, all these X/XO-induced effects were also observed in cells pretreated with pyrogallol, also an O(-2) donor. These results indicate that O(-2) impairs at least two mechanisms involved in Ca(2+) mobilization in human nasal epithelial cells, i.e., CRAC and ATP-induced Ca(2+) release.

Adenosine Triphosphate↗
PubMed2001

Reactive oxygen species stimulate VEGF production from C(2)C(12) skeletal myotubes through a PI3K/Akt pathway.

Vascular endothelial growth factor (VEGF) is a potent angiogenic stimulus, the expression of which increases in skeletal muscle after exercise. Because exercise is also accompanied by increased intramuscular reactive oxygen species (ROS) generation, we tested the hypothesis that ROS stimulate VEGF production from skeletal myotubes. Differentiated C(2)C(12) skeletal myotubes exposed to ROS-producing agents exhibited a concentration-dependent increase in VEGF production, whereas undifferentiated myoblasts did not respond to oxidants. Moreover, conditioned medium from ROS-treated myotubes increased the bovine lung microvascular cell proliferation rate. To study the mechanism(s) involved in the stimulation of VEGF production by ROS, myotubes were pretreated with a selective phosphatidylinositol 3-kinase (PI3K) inhibitor, LY-294002, before being exposed to hydrogen peroxide or pyrogallol. LY-294002 attenuated both Akt phosphorylation and VEGF production. In addition, oxidants increased nuclear factor-kappaB-dependent promoter activity in transiently transfected myotubes; however, pretreatment with the pharmacological inhibitor of nuclear factor-kappaB, diethyldithiocarbamate, did not affect the oxidant-stimulated VEGF release. We conclude that ROS induce VEGF release from myotubes via a PI3K/Akt-dependent pathway.

Animals↗
PubMed1991

Pulmonary vascular response to endothelin in rats.

This study investigated the pulmonary vascular response to endothelin (ET) in rats. In conscious rats, an incremental intravenous bolus of ET-1 (100-1,000 pM) caused, after an initial drop in systemic arterial pressure (Psa), a secondary dose-dependent increase of Psa concomitant with a decrease of cardiac output (CO) and heart rate (HR). Pulmonary arterial pressure (Ppa) remained unchanged, and pulmonary vascular resistance (PVR) increased significantly only after 1,000 pM (+ 40.0 +/- 10.4 at 15 min). Meclofenamate (6 mg/kg iv) did not alter hemodynamic response to ET (300 pM). After autonomic blockade with hexamethonium (6 mg/kg iv) plus atropine (0.75 mg/kg iv), bradycardia response to ET (300 pM) was blocked, but CO decreased, systemic vascular resistance increased, and PVR remained unchanged as in controls. In anesthetized ventilated rats, bolus injections of ET (10-1,000 pM) induced a transient dose-related decrease in compliance (-10.9 +/- 1.8% after 1,000 pM) but no change of conductance. In isolated lungs, Ppa increased at doses greater than 100 pM, and edema developed in response to 1,000 pM ET. The rise of Ppa in response to 300 pM was not altered by meclofenamate (3.2 x 10(-6) M) but was potentiated by inhibitors of endothelium-derived relaxing factor(s) (EDRF), methylene blue (10(-4) M), pyrogallol (3 x 10(-5) M), and NG-monomethyl-L-arginine (6 x 10(-4) M) (3.9 +/- 0.3, 4.6 +/- 0.5, and 5.9 +/- 0.3 mmHg, respectively, compared with 1.5 +/- 0.5 mmHg in control lungs). These results suggest that circulating ET is a more potent constrictor of the systemic circulation than of the pulmonary vascular bed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗