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At least 811 records · Page 45Linked to original sources
PubMed1984

Genetic mode of action of cocarcinogens and tumor promoters in yeast and mice.

In experiments with yeast, cocarcinogens were found to be comutagenic and antirecombinogenic , tumor promoters to be corecombinogenic and antimutagenic. Substances that were cocarcinogens as well as tumor promoters had an intermediary effect. These results were confirmed in the mammalian spot test: By in vivo treatment of mice with the cocarcinogen catechol and the tumor promoter limonene carcinogen-induced recombination due to mitotic crossing over and gene mutations was reduced and enhanced, respectively. Our results support the hypothesis that mutagenesis is the mechanism by which chemicals induce malignancy, and that cocarcinogens modify the process by enhancement of mutagenicity whereas tumor promoters effect carcinogenesis by increase of the spontaneous frequency of recombination. In addition, induced mitotic recombination in mammals in vivo has been demonstrated for the first time.

Acridine Orange↗
PubMed2003

Inhibition of inducible nitric oxide synthase and cyclooxygenase-2 activity by 1,2,3,4,6-penta-O-galloyl-beta-D-glucose in murine macrophage cells.

Activated macrophages express inducible isoforms of nitric oxide synthase (iNOS) and cyclooxygenase (COX-2), and produce excessive amounts of nitric oxide (NO) and prostaglandin E2 (PGE2), which play key roles in the processes of inflammation and carcinogenesis. The root of Paeonia lactiflora Pall., and the root cortex of Paeonia suffruticosa Andr., are important Chinese crude drugs used in many traditional prescriptions. 1,2,3,4,6-penta-O-galloyl-beta-D-glucose (PGG) is a major bioactive constituent of both crude drugs. PGG has been shown to possess potent anti-oxidant, anti-mutagenic, anti-proliferative and anti-invasive effects. In this study, we examined the inhibitory effects of 1,2,3,4,6-penta-O-galloyl-beta-D-glucose (PGG) isolated from the root of Paeonia lactiflora Pall. on the COX-2 and iNOS activity in LPS-activated Raw 264.7 cells, COX-1 in HEL cells. To investigate the structure-activity relationships of gallate and gallic acid for the inhibition of iNOS and COX-2 activity, we also examined (-)-epigallocatechin gallate (EGCG), gallic acid, and gallacetophenone. The results of the present study indicated that PGG, EGCG, and gallacetophenone treatment except gallic acid significantly inhibited LPS-induced NO production in LPS-activated macrophages. All of the four compounds significantly inhibited COX-2 activity in LPS-activated macrophages. Among the four compounds examined, PGG revealed the most potent in both iNOS (IC50 approximately 18 microg/mL) and COX-2 inhibitory activity (PGE2: IC50 approximately 8 microg/mL and PGD2: IC50 approximately 12 microg/mL), respectively. Although further studies are needed to elucidate the molecular mechanisms and structure-activity relationship by which PGG exerts its inhibitory actions, our results suggest that PGG might be a candidate for developing anti-inflammatory and cancer chemopreventive agents.

Acetophenones↗
PubMed2003

Purification and characterization of laccase from the white-rot fungus Daedalea quercina and decolorization of synthetic dyes by the enzyme.

The white-rot fungus Daedalea quercina produced the ligninolytic enzymes laccase and Mn-dependent peroxidase. Laccase was purified using anionexchange and size-exclusion chromatographies. SDS-PAGE showed the purified laccase to be a monomeric protein of 69 kDa (71 kDa using gel filtration) with an isoelectric point near 3.0. The optimum pH for activity was below 2.0 for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (K(m)=38 microM), 4.0 for 2,6-dimethoxyphenol (K(m)=48 microM), 4.5 for guaiacol (K(m)=93 microM) and 7.0 for syringaldazine (K(m)=131 microM). The temperature optimum was between 60 and 70 degrees C depending on the pH and buffer used. The enzyme was stable up to 45 degrees C, and stability was higher at alkaline pH. Enzyme activity was increased by the addition of Cu(2+) and inhibited by Mn(2+), sodium azide, dithiothreitol, and cysteine. Laccase from Daedalea quercina was able to decolorize the synthetic dyes Chicago sky blue, poly B-411, remazol brilliant blue R, trypan blue and reactive blue 2.

Anthraquinones↗
PubMed2005

The white-rot fungus Cerrena unicolor strain 137 produces two laccase isoforms with different physico-chemical and catalytic properties.

Cerrena unicolor secreted two laccase isoforms with different characteristics during the growth in liquid media. In a synthetic low-nutrient nitrogen glucose medium (Kirk medium), high amounts of laccase (4,000 U l(-1)) were produced in response to Cu2+. Highest laccase levels (19,000 U l(-1)) were obtained in a complex tomato juice medium. The isoforms (Lacc I, Lacc II) were purified to homogeneity with an overall yield of 22%. Purification involved ultrafiltration and Mono Q separation. Lacc I and II had M (w) of 64 and 57 kDa and pI of 3.6 and 3.7, respectively. Both isoforms had an absorption maximum at 608 nm but different pH optima and thermal stability. Optimum pH ranged from 2.5 to 5.5 depending on the substrate. The pH optima of Lacc II were always higher than those of Lacc I. Both laccases were stable at pH 7 and 10 but rapidly lost activity at pH 3. Their temperature optimum was around 60 degrees C, and at 5 degrees C they still reached 30% of the maximum activity. Lacc II was the more thermostable isoform that did not lose any activity during 6 months storage at 4 degrees C. Kinetic constants (K (m), k (cat)) were determined for 2,2'-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS), 2,6-dimethoxyphenol and syringaldazine.

Benzothiazoles↗
PubMed2006

Differential regulation of manganese peroxidases and characterization of two variable MnP encoding genes in the white-rot fungus Physisporinus rivulosus.

Manganese peroxidase (MnP) production in the white-rot basidiomycete Physisporinus rivulosus T241i was studied. Separate MnP isoforms were produced in carbon-limited liquid media supplemented with Mn(2+), veratryl alcohol, or sawdust. The isoforms had different pH ranges for the oxidation of Mn(2+) and 2,6-dimethoxyphenol. Although lignin degradation by white-rot fungi is often triggered by nitrogen depletion, MnPs of P. rivulosus were efficiently produced also in the presence of high-nutrient nitrogen, especially in cultures supplemented with veratryl alcohol. Two MnP encoding genes, mnpA and mnpB, were identified, and their corresponding cDNAs were characterized. Structurally, the genes showed marked dissimilarity, and the expression of the two genes implicated quantitative variation and differential regulation in response to manganese, veratryl alcohol, or sawdust. The variability in regulation and properties of the isoforms may widen the operating range for efficient lignin degradation by P. rivulosus.

Amino Acid Sequence↗
PubMed2006

Purification and characterization of laccase from Pycnoporus sanguineus and decolorization of an anthraquinone dye by the enzyme.

The white rot fungus Pycnoporus sanguineus produced high amount of laccase in the basal liquid medium without induction. Laccase was purified using ultrafiltration, anion-exchange chromatography, and gel filtration. The molecular weight of the purified laccase was estimated as 61.4 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme oxidized typical substrates of laccases including 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonate), 2,6-dimethoxyphenol, and syringaldazine. The optimum pH and temperature for the purified laccase were 3.0 and 65 degrees C, respectively. The enzyme was stable up to 40 degrees C, and high laccase activity was maintained at pH 2.0-5.0. Sodium azide, L-cysteine, and dithiothreitol strongly inhibited the laccase activity. The purified enzyme efficiently decolorized Remazol Brilliant Blue R in the absence of added redox mediators. The high production of P. sanguineus laccase as well as its decolorization ability demonstrated its potential applications in dye decolorization.

Anthraquinones↗
PubMed2006

Molecular and enzymatic characterisation of extra- and intracellular laccases from the acidophilic ascomycete Hortaea acidophila.

The pigmented ascomycete Hortaea acidophila is able to grow at a pH as low as 0.6 and produces laccases that are involved in melanin synthesis. We now present data on an extracellular and an intracellular laccase which exhibit a high stability at low pH. Furthermore, the optimum for enzyme acitivity is extraordinarily low with pH 1.5 for the intracellular laccase with 2,6-dimethoxyphenol (DMOP) as substrate. Two complete laccase gene sequences of H. acidophila were amplified by inverse polymerase chain reaction (PCR). Whereas the deduced protein laccase I contains an predicted N-terminal signal sequence for protein export, laccase II does not and thus may represent the intracellular laccase. The acidophilic character of both laccases seems to be reflected in their primary structure.

Amino Acid Sequence↗
PubMed2005

Differential patterns of constitutive intracellular laccases of the vegetative phase of Pleurotus species.

The constitutive intracellular laccase activity of ten strains of Pleurotus spp. was determined in vitro and by zymograms, using different substrates. Differences in the in vitro activities were observed between all the strains; however, zymogram patterns were only similar for strains within same species, independently of any of the three substrate (2,6-dimethoxyphenol, p-anisidine or o-tolidine) used. The differences observed in the number and positions of the isoforms in the gel suggest that laccase zymograms can be used to differentiate species of this organism.

Aniline Compounds↗