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At least 811 records · Page 45Linked to original sources
PubMed1990

Chloromethane, Methyl Donor in Veratryl Alcohol Biosynthesis in Phanerochaete chrysosporium and Other Lignin-Degrading Fungi.

Chloromethane, a gaseous natural product implicated in methylation processes in Phellinus pomaceus, has been shown to act as methyl donor in veratryl alcohol biosynthesis in the lignin-degrading fungi Phanerochaete chrysosporium, Phlebia radiata, and Coriolus versicolor, none of which released detectable amounts of CH(3)Cl during growth. When P. chrysosporium was grown in a medium containing CH(3)Cl, levels of CH(3) incorporation into the 3- and 4-O-methyl groups of veratryl alcohol were very high and initially similar to those observed when the medium was supplemented with l-[methyl-H(3)]methionine. When CH(3)Cl was added to cultures actively synthesizing veratryl alcohol, incorporation of CH(3) was very rapid, with 81% of veratryl alcohol labeled after 12 h. By contrast, incorporation of CH(3) from l-[methyl-H(3)]methionine was comparatively slow, attaining 10% after 12 h. It is proposed that these lignin-degrading fungi possess a tightly channeled multienzyme system in which CH(3)Cl biosynthesis is closely coupled to CH(3)Cl utilization for methylation of veratryl alcohol precursors.

Journal Article↗
PubMed1993

Decolorization of Azo, Triphenyl Methane, Heterocyclic, and Polymeric Dyes by Lignin Peroxidase Isoenzymes from Phanerochaete chrysosporium.

The ligninolytic enzyme system of Phanerochaete chrysosporium decolorizes several recalcitrant dyes. Three isolated lignin peroxidase isoenzymes (LiP 4.65, LiP 4.15, and LiP 3.85) were compared as decolorizers with the crude enzyme system from the culture medium. LiP 4.65 (H2), LiP 4.15 (H7), and LiP 3.85 (H8) were purified by chromatofocusing, and their kinetic parameters were found to be similar. Ten different types of dyes, including azo, triphenyl methane, heterocyclic, and polymeric dyes, were treated by the crude enzyme preparation. Most of the dyes lost over 75% of their color; only Congo red, Poly R-478, and Poly T-128 were decolorized less than the others, 54, 46, and 48%, respectively. Five different dyes were tested for decolorization by the three purified isoenzymes. The ability of the isoenzymes to decolorize the dyes in the presence of veratryl alcohol was generally comparable to that of the crude enzyme preparation, suggesting that lignin peroxidase plays a major role in the decolorization and that manganese peroxidase is not required to start the degradation of these dyes. In the absence of veratryl alcohol, the decolorization activity of the isoenzymes was in most cases dramatically reduced. However, LiP 3.85 was still able to decolorize 20% of methylene blue and methyl orange and as much as 60% of toluidine blue O, suggesting that at least some dyes can function as substrates for isoenzyme LiP 3.85 but not to the same extent for LiP 4.15 or LiP 4.65. Thus, the isoenzymes have different specificities towards dyes as substrates.

Journal Article↗
PubMed1993

Xylosylation of Phenolic Hydroxyl Groups of the Monomeric Lignin Model Compounds 4-Methylguaiacol and Vanillyl Alcohol by Coriolus versicolor.

When 4-methylguaiacol (MeG), a phenolic lignin model compound, was added to a culture that was inoculated with Coriolus versicolor, it was bioconverted into 2-methoxy-4-methylphenyl beta-d-xyloside (MeG-Xyl). The phenolic hydroxyl group of vanillyl alcohol was much more extensively xylosylated than the alcoholic hydroxyl group. When a mixture of MeG and commercial UDP-xylose was incubated with cell extracts of mycelia, transformation of UDP-xylose into MeG-Xyl was observed. This result suggested that UDP-xylosyltransferase was involved in the xylosylation of phenolic hydroxyl groups of lignin model compounds.

Journal Article↗
PubMed1996

Lip-like genes in Phanerochaete sordida and Ceriporiopsis subvermispora, white rot fungi with no detectable lignin peroxidase activity.

Lignin peroxidase-like genes were PCR amplified from Phanerochaete sordida and Ceriporiopsis subvermispora, fungi lacking lignin peroxidase (LiP) activity. Amplification products were highly similar to previously described LiP genes. Using reverse transcription-coupled PCR a LiP-like cDNA clone was amplified from P. sordida RNA. In contrast, no evidence was obtained for transcription of C. subvermispora LiP genes.

Amino Acid Sequence↗
PubMed1998

Effects of manganese peroxidase on residual lignin of softwood kraft pulp

Manganese peroxidase treatment lowered the kappa number of kraft pulp and increased the alkali extractability of the residual lignin but did not directly solubilize it. This indicates that MnP partially oxidizes the lignin in the pulp but does not degrade it to soluble fragments.

Journal Article↗
PubMed1993

Lignified materials as medicinal resources. VI. Anti-HIV activity of dehydrogenation polymer of p-coumaric acid, a synthetic lignin, in a quasi-in-vivo assay system as an intermediary step to clinical trials.

After the dehydrogenation polymer of p-coumaric acid, a synthetic lignin, was intravenously injected into mice, the serum was collected immediately, 15 min, 1 h, 5 h, and 24 h after the injection. The serum thus obtained was added to the assay medium containing MT-4 cells infected with HTLV-IIIB (an HIV-1 strain). Inhibition of the cytopathogenicity of HIV by these serum preparations was assayed by the MTT method. The result revealed that lignins could be a promising class of anti-HIV agents with an unidentified unique mode of action.

Antiviral Agents↗
PubMed2001

Photostabilizing milled wood lignin with benzotriazoles and hindered nitroxide.

The inhibitory processes operating when a 2(-2'-hydroxyphenyl) benzotriazole-based ultraviolet absorber (UVA) and a hindered nitroxide free radical are applied to high-yield pulps were studied using milled wood lignin and filter paper as a model. Using quantitative 31P NMR it was determined that the UVA is almost completely photostable during irradiation, suggesting that its protective mechanism is based primarily on ultraviolet absorption. Furthermore, the nitroxide was found to protect the UVA from photodegradation. Analysis of irradiated lignin samples involved derivatization followed by reductive cleavage of beta-arylether groups. The phenolic-OH groups thus released were quantified using 31P NMR. The benzotriazole/nitroxide stabilizing system was found to cooperatively inhibit the cleavage of beta-arylether groups. Furthermore, this system was found to have a synergistic inhibitory effect on the formation of catechol structures. These results suggest that the synergism observed between benzotriazole-based UV screens and nitroxyl radicals on the inhibition of yellowing could be a result of their ability to slow the formation of catechol structures and beta-O-4 cleavage in addition to the possibility of a UVA-regeneration mechanism.

Journal Article↗
PubMed1999

Analysis of 5' Upstream Regulatory Sequences of Lignin Peroxidase(LIP) Genes of Phanerochaete chrysosporium.

Phanerochaete chrysosporium yields exocellular isozymes of lignin peroxidases and Mn peroxidases which are able to degrade lignin. In order to investigate the regulatory mechanism of LIP genes at transcriptional level, 6 DNA fragments subcloned from 5' upstream sequences of LIP genes (GLG3 and GLG6) were obtained, then gel mobility shift assay was carried out to screen DNA fragment(s) with ability to be bound specifically by proteins isolated from P.chrysosporium mycelia. The results showed that a 670 bp DNA fragment localized upstream of a LIP gene GLG6 was capable of being bound specifically by protein component, and analysis of its nucleotide sequence indicated that the DNA fragment contains the putative sequence characteristic of protein binding site. This result suggests that protein(s) in this fungus interact with the putative cis-element(s) in the 5' upstream sequence of LIP genes, regulating the expression of LIP genes.

Journal Article↗
PubMed1988

Studies on compound I formation of the lignin peroxidase from Phanerochaete chrysosporium.

Ligninase, isolated from the wood-destroying fungus Phanerochaete chrysosporium, catalyzes the oxidation of lignin and lignin-related compounds. Ligninase reacts with H2O2 to form the classical peroxidase intermediates Compounds I and II. We have determined the activation energy of ligninase Compound I formation to be 5.9 kcal/mol. The effect of pH and ionic strength on the rate of ligninase Compound I formation was studied. In contrast to all other peroxidases, no pH effect was observed. This is despite homology of active-site amino acids residues (Tien, M., and Tu, C.-P. D. (1987) Nature 326, 520-523) which are proposed to affect the pH profile of Compound I formation. Ligninase Compound I formation can also be supported by organic peroxides. The second-order rate constants with the organic peroxides are lower, suggesting that H2O2 is the preferred substrate.

Amino Acid Sequence↗
PubMed1988

Spectroscopic and kinetic properties of the oxidized intermediates of lignin peroxidase from Phanerochaete chrysosporium.

Stopped-flow rapid scan techniques were used to obtain a spectrum of nearly homogeneous lignin peroxidase compound I (LiPI) under pseudo-first order conditions at the unusually low pH optimum (3.0) for the enzyme. The LiPI spectrum had a Soret band at 407 nm with approximately 60% reduced intensity and a visible maximum at 650 nm. Under steady-state conditions a Soret spectrum for lignin peroxidase compound II (LiPII) was also obtained. The Soret maximum of LiPII at 420 nm was only approximately 15% reduced in intensity compared to native LiP. Transient state kinetic results confirmed the pH independence of LiPI formation over the pH range 3.06-7.39. The rate constant was (6.5 +/- 0.2) x 10(5) M-1 S-1. Addition of excess veratryl alcohol to LiPI resulted in its reduction to LiPII with subsequent reduction of LiPII to the native enzyme. Reactions of LiPI and LiPII with veratryl alcohol exhibited marked pH dependencies. For the LiPI reaction the rate constants ranged from 2.5 x 10(6) M-1 S-1 at pH 3.06 to 4.1 x 10(3) M-1 S-1 at pH 7.39; for the LiPII reaction, 1.6 x 10(5) M-1 S-1 (pH 3.06) to 2.3 x 10(3) M-1 S-1 (pH 5.16). These single turnover experiments demonstrate directly that the pH dependence of these reactions dictates the overall pH dependence of this novel enzyme. These results are consistent with the one-electron oxidation of veratryl alcohol to an aryl cation radical by LiPI and by LiPII.

Agaricales↗
PubMed1993

Veratryl alcohol-dependent production of molecular oxygen by lignin peroxidase.

Veratryl alcohol- and H2O2-dependent production of oxygen by lignin peroxidase isozyme H2 (LiPH2) from Phanerochaete chrysosporium was investigated. Veratryl alcohol oxidation by LiPH2 decreased with increasing concentrations of H2O2 while oxygen evolution increased. The absorption spectrum of the LiPH2 in these experiments indicated that it was in the compound II state. We propose that O2 production results from the one electron oxidation of H2O2 by the veratryl alcohol cation radical to yield superoxide, as the addition of superoxide dismutase stimulated oxygen production. It has been reported previously that oxygen is consumed in reaction mixtures containing lignin peroxidase, H2O2, veratryl alcohol, and oxalate (Popp, J. L., Kalyanaraman, B., and Kirk, T.K. (1990) Biochemistry 29, 10475-10480). In the presence of oxalate, we observed oxygen consumption that was dependent on the H2O2 concentration. The ability of other methoxybenzenes to mediate oxygen production appeared to be related to their redox potential. It was concluded that cation radicals can oxidize H2O2 by one electron which results in the production of superoxide and the evolution of molecular oxygen. Thus, the rates of LiPH2-catalyzed O2 consumption or O2 production are dependent on the relative concentrations of H2O2 and oxalate.

Agaricales↗
PubMed2000

X-ray structure of a trimeric 5,5'-biaryl/erythro-beta-O-4-ether lignin model: evidence for through-space weak interactions.

The crystal structure of a trimeric lignin model 1 presenting the characteristic pattern of biphenyl (5,5') and aryl-alkyl-ether (beta-O-4) linkages has been determined. The crystal system is triclinic and the crystallographic unit cell consists of two monomeric molecules. These results are compared with crystal data from the literature of simple models of the 5,5' and beta-O-4 structure type. The availability of a terminal aldehyde function on the model affords some interesting intermolecular interactions by weak hydrogen bonding which controls the conformation of the molecule and the aromatic ring orientation in particular; an unexpected cisoïd conformation of the biaryl unit is observed based on the 64.4 degrees value found for the torsion angle between the two 5,5' aromatic rings.

Alcohols↗
PubMed2004

Molecular dynamics simulations of a guaiacyl beta-O-4 lignin model compound: examination of intramolecular hydrogen bonding and conformational flexibility.

The dynamical conformational behavior of a guaiacyl beta-O-4 lignin model compound has been investigated by molecular simulations. The potential energy surface of the molecule in vacuum has been examined by means of an adiabatic map, showing a large accessible conformational space with multiple energy minima separated by low barriers. Molecular dynamics simulations have been performed in vacuum and with explicit solvent molecules for 10 and 2.1 ns, respectively. Molecular dynamics trajectories recorded in vacuum have shown the molecule to be flexible and to visit a large number of conformations. Many intramolecular H-bonds have been observed, existing for more than 90% of the total simulation time. The presence of explicit solvent molecules induces a significant broadening of some regions of the accessible conformational space and also largely reduces the statistical significance of intramolecular H-bonding. Intramolecular H-bonds observed in vacuum do not persist significantly and are preferentially exchanged with intermolecular H-bonds to the surrounding solvent molecules. The theoretical results are in good agreement with experimental NMR data that do not support the existence of strong and persistent intramolecular H-bonds in solution but instead indicate that H-bonds to solvent predominate. Finally, both molecular modeling and NMR approaches predict the guaiacyl beta-O-4 structure to be flexible and indicate that intramolecular H-bonds are not strong and persistent enough to confer rigidity to the molecule in solution.

Guaiacol↗
PubMed1993

The effect of the fiber components cellulose and lignin on experimental colon neoplasia.

Sixty Sprague-Dawley rats were pair-fed one of three nutritionally identical diets. One diet contained "low-fiber" (3.8% crude fiber); the others contained "high fiber" (28.7% crude fiber) composed of either cellulose or lignin. Although both "high fiber" diets had similar stool bulking effects, only the cellulose diet was associated with a reduction in 1,2-dimethylhydrazine (DMH)-induced colon neoplasms. The cellulose diet was also associated with distinct changes in the gut bacterial profile and with a lowered serum cholesterol.

1,2-Dimethylhydrazine↗
PubMedDate not supplied

Capillary zone electrophoresis of syringyl and guaiacyl monomers resulting from lignin thioacidolysis.

A capillary zone electrophoretic method has been developed for the quantitative determination of syringyl (S) and guaiacyl (G) monomers resulting from lignin thioacidolysis. The effects on the separation of altering a number of parameters have been investigated, resulting in an efficient and rapid separation. Analysis times were about 10 min instead of 50 min for the conventional GC methods, with no requirement for a derivatisation step prior to analysis. Relative standard deviations ranged between 8 and 12% for the absolute determination of S and G monomers, and between 1.4 and 3.5% for the S/G ratio.

Algorithms↗
PubMed2005

Metabolic regulation at the tricarboxylic acid and glyoxylate cycles of the lignin-degrading basidiomycete Phanerochaete chrysosporium against exogenous addition of vanillin.

A proteomic differential display technique was utilized to study cellular responses of Phanerochaete chrysosporium exposed to vanillin, one of the key intermediates found during lignin biodegradation. Intracellular proteins were resolved by 2-DE and target protein spots were identified using MALDI-MS after in-gel tryptic digestions. Upon addition of vanillin to P. chrysosporium, up-regulation of homogentisate 1,2-dioxygenase, 1,4-benzoquinone reductases, aldehyde dehydrogenase, and aryl-alcohol dehydrogenase, which seem to play roles in vanillin metabolism, was observed. Furthermore, enzymes involved in glycolysis, the tricarboxylic acid cycle, the pentose-phosphate cycle, and heme biosynthesis were also activated. Up-regulation of extracellular peroxidase was also observed. One of the most unique phenomena against exogenous vanillin was a switch from the glyoxylate cycle to the tricarboxylic acid cycle, where a drastic increase in isocitrate dehydrogenase activity was observed. The exogenous addition of other aromatic compounds also caused an increase in its activity, which in turn triggered NAD(P)H production via the action of dehydrogenases in the tricarboxylic acid cycle, heme biosynthesis via the action of aminolevulinic acid synthase on succinyl-CoA, and energy production via activation of the mitochondrial electron transfer system. These metabolic shifts seem to be required for activating a metabolic system for aromatic compounds.

Alcohol Oxidoreductases↗
PubMed1995

Veratryl alcohol-mediated indirect oxidation of phenol by lignin peroxidase.

Veratryl alcohol (VA) oxidation by lignin peroxidase (LiP) was inhibited by phenol. The enzyme was quickly converted to compound III, an inactive intermediate. However, as soon as VA began to be oxidized, compound II was observed. The lag period before VA oxidation was affected by the concentrations of both phenol and VA. The addition of VA increased the extent of phenol oxidation and the kinetics of phenol oxidation in the presence of VA were similar to those of VA oxidation. Previously it was shown that the VA cation radical (VA.+) was responsible for the conversion of compound III back to ferric enzyme [D. P. Barr and S. D. Aust (1994) Arch. Biochem. Biophys. 312, 511-515]. Here we observed that the reversion of compound III to active ferric enzyme in the presence of VA was prevented by addition of phenol, suggesting that VA.+ oxidizes phenol to phenoxyl radical. This hypothesis was also supported by the observation that O2 consumption during VA oxidation was inhibited by the addition of phenol. All of these results suggested that VA was first oxidized by LiP to VA.+ and then it oxidized phenol to phenoxyl radical while VA.+ was reduced back to VA. Activity was lost as compound III accumulated since the VA.+ was consumed by the oxidation of phenol. After all of the phenol was oxidized, VA.+ became available to convert compound III back to ferric enzyme.

Benzyl Alcohols↗