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PubMed1994

Effects of manganese deficiency on soluble apoplastic peroxidase activities and lignin content in needles of Norway spruce (Picea abies).

Apoplastic peroxidase activities were investigated in manganese-deficient and manganese-sufficient needles of field-grown Norway spruce trees (Picea abies L.). In Mn-sufficient needles, two sets of peroxidases, one with an alkaline pI >/= 9 and another with an acidic pI </= 3, were identified using guaiacol or coniferylalcohol as substrates for activity staining after isoelectric focusing in a pH gradient from 3 to 9. The acidic peroxidases were capable of Mn-dependent NADH oxidation and H(2)O(2) formation. Syringaldazine peroxidase activity was not found in apoplastic extracts, but was present in whole-needle extracts. Manganese deficiency did not affect the activity or the isoelectric focusing pattern (pH 3 to 9) of the apoplastic peroxidases. Soluble peroxidase activities from whole-needle extracts were significantly higher in Mn-deficient than in Mn-sufficient needles with all substrates tested. Mn-deficient needles contained slightly less cell wall material than Mn-sufficient needles, but the lignin content was similar. Neither apoplastic peroxidase activity nor lignification was affected by Mn deficiency, suggesting that apoplastic peroxidases are regulated independently from symplastic peroxidases.

Journal Article↗
PubMed1991

Isolation and structural analysis of the laccase gene from the lignin-degrading fungus Phlebia radiata.

We have isolated and characterized a gene coding for the laccase of the lignin-degrading fungus Phlebia radiata. The gene has nine introns and recognizable fungal promoter elements. Sequences homologous to the consensus eukaryotic heat-shock regulatory element can be found in the promoter. RNA hybridization results indicate that this gene is regulated at the transcriptional level. The derived laccase amino acid sequence shows homology to plant ascorbate oxidases, suggesting that the basic structure of the laccase is similar to the three-fold repeated beta-barrel of the ascorbate oxidases. Potential copper ligands and a residue carrying the prosthetic group pyrroloquinoline quinone (PQQ) in the laccase protein can be identified by homology. The intron/exon structure of the laccase gene suggests that this protein could have evolved by exon shuffling.

Amino Acid Sequence↗
PubMed2000

Disordered ultrastructure in lignin-peroxidase-secreting hyphae of the white-rot fungus Phanerochaete chrysosporium.

The practice of exposing liquid cultures of the white-rot fungus Phanerochaete chrysosporium to a pure oxygen atmosphere under conditions of nutrient starvation has been widely adopted to induce lignin peroxidase (LiP) synthesis. Transmission electron microscopy was used to examine hyphal cells of carbon-limited cultures that had been exposed to an atmosphere of pure oxygen, and revealed evidence of a major loss in organization of cellular ultrastructure, which may be attributed to oxygen toxicity. Under some conditions (continuous agitation in air with cellulose as the carbon source) cultures will produce LiP without needing to be exposed to a pure oxygen atmosphere. A similar major loss of cellular ultrastructure was found in hyphal cells from such cultures upon examination. Investigation of the levels of H2O2, catalase and carbonyl content of intracellular proteins suggests that the latter cultures developed a hyperoxidant state because the rate of supply of carbon from cellulose hydrolysis was insufficient for oxygen homeostasis. The association of LiP with these cultures and with those exposed to an atmosphere of pure oxygen infers that LiP may be triggered in response to oxidant stress.

Carbon↗
PubMed1976

Soluble and cell wall peroxidases in reed canarygrass in relation to disease resistance and localized lignin formation.

The relationship of peroxidases to an inducible disease-resistance mechanism involving lignification of leaf epidermal cell walls was studied. Reed canarygrass (Phalaris arundinacea L.) leaf discs were inoculated with Helminthosporium avenae Eidam and floated on water. In inoculated discs, the activity of soluble, ionic wall-bound and covalent wall-bound peroxidases was about twice the level of activity in noninoculated discs. The increase was attributable to increases in activity of three cathodic isoperoxidases and to the appearance of a new cathodic isoperoxidase. Peroxidase activity in cryostat microtome sections of inoculated discs was histochemically localized in the wall near the site of attempted penetration. When inoculated discs were floated on solutions of cycloheximide (25 mug/ml), increases in peroxidase activity were inhibited, and the fungus penetrated the tissue. The inhibition of peroxidase activity was related to inhibition of cathodic isoperoxidase activity. Anodic isoperoxidase activity did not show changes in response to inoculation or cycloheximide treatment.It was suggested that the resistance mechanism in P. arundinacea involves an induction of cathodic isoperoxidases in challenged tissue. These peroxidases may function in the biosynthesis of lignin at the site of attempted penetration.

Journal Article↗
PubMed1991

Stress Responses in Alfalfa (Medicago sativa L.): X. Molecular Cloning and Expression of S-Adenosyl-l-Methionine:Caffeic Acid 3-O-Methyltransferase, a Key Enzyme of Lignin Biosynthesis.

S-Adenosyl-l-methionine:caffeic acid 3-O-methyltransferase (COMT, EC 2.1.1.6) catalyzes the conversion of caffeic acid to ferulic acid, a key step in the biosynthesis of lignin monomers. We have isolated a functionally active cDNA clone (pCOMT1) encoding alfalfa (Medicago sativa L.) COMT by immunoscreening a lambdaZAPII cDNA expression library with anti-(aspen COMT) antibodies. The derived amino acid sequence of pCOMT1 is 86% identical to that of COMT from aspen. Southern blot analysis indicates that COMT in alfalfa is encoded by at least two genes. Addition of an elicitor preparation from bakers' yeast to alfalfa cell suspension cultures resulted in a rapid accumulation of COMT transcripts, which reached a maximum level around 19 hours postelicitation. Northern blot analysis of total RNA from different organs of alfalfa plants at various developmental stages showed that COMT transcripts are most abundant in roots and stems. Transcripts encoding ATP: i-methionine-S-adenosyl transferase (AdoMet synthetase, EC 2.5.1.6), the enzyme responsible for the synthesis of the methyl donor for the COMT reaction, were coinduced with COMT transcripts in elicitor-treated cells and exhibited a similar pattern of expression to that of COMT in different organs of alfalfa plants at various stages of development.

Journal Article↗
PubMed1989

RFLP-based genetic map of Phanerochaete chrysosporium ME446: lignin peroxidase genes occur in clusters.

We describe the construction of an RFLP-based genetic map of the white rot fungus Phanerochaete chrysosporium ME446. The map is deduced from the allele distributions of 38 RFLP markers in a test set of 53 meiotically derived haploid recombinants of this strain. The map includes a cellulase gene, a matingtype locus and a family of lignin peroxidase (and related) genes that are arranged in two unlinked clusters.

Alleles↗
PubMed1996

Oxidation of dimethoxylated aromatic compounds by lignin peroxidase from Phanerochaete chrysosporium.

The stabilities of the cation radicals of veratryl alcohol, 3,4-dimethoxytoluene and 1,4-dimethoxybenzene were compared by monitoring the formation of dimeric products during the oxidation of these substrates by lignin peroxidase (LiP). LiP oxidized veratryl alcohol to generate veratraldehyde as the major product. Several other monomeric products were obtained in low yield. Dimeric products resulting from the coupling of two cation radicals, or a cation radical with a neutral molecule, were obtained only in trace amounts or not at all. This suggests that the cation radical of veratryl alcohol rapidly loses a benzylic proton to form a benzylic radical which undergoes further reactions to form veratraldehyde. In contrast, the LiP oxidation of 3,4-dimethoxytoluene generated the dimeric product 3-(2,3-dimethoxy-6-methylphenyl)-4-methyl-1,2-benzoquinone as the major product. Several other monomeric and dimeric products were produced in lower yields. The generation of these dimeric products indicates that the cation radical of 3,4-dimethoxytoluene is considerably more stable than that of veratryl alcohol. This suggests that the electronegative benzylic oxygen of veratryl alcohol increases the acidity of the benzylic protons, destabilizing the veratryl alcohol cation radical. LiP oxidized 1,4-dimethoxybenzene to generate 1,4-benzoquinone and 2-(2,5-dimethoxyphenyl)-1,4-benzoquinone as the major products. The formation of these products indicates that the cation radical of 1,4-dimethoxybenzene also is relatively stable, as previously demonstrated by ESR. All of these results indicate that the veratryl alcohol cation radical generated by LiP oxidation is unstable, suggesting that it would not act as a diffusable radical mediator in LiP-catalyzed reactions.

Anisoles↗
PubMed1980

Methanogenic decomposition of ferulic Acid, a model lignin derivative.

Ferulic acid, a model lignin derivative, was observed to be biodegradable to methane and carbon dioxide under strict anaerobic conditions. This conversion appears to be carried out by a consortium of bacteria similar to that previously described for the methanogenic degradation of benzoic acid. A temporary buildup of acetate in these cultures indicates that it is a likely intermediate and precursor for methane formation. An analog of coenzyme M, 2-bromoethanesulfonic acid (BESA), inhibited gas production and enhanced the buildup of propionate, butyrate, isobutyrate, and isovalerate. Phenylacetate, cinnamate, 3-phenylpropionate, benzoate, cyclohexane carboxylate, adipate, and pimelate were also detected in BESA-inhibited cultures. A pathway is proposed which includes these various acids as possible intermediates in the methanogenic degradation of ferulic acid. This model overlaps previously described benzoic acid degradation pathways, suggesting that this type of anaerobic degradation may be common for aromatic compounds.

Journal Article↗
PubMed1980

Metabolism of Radiolabeled beta-Guaiacyl Ether-Linked Lignin Dimeric Compounds by Phanerochaete chrysosporium.

Phanerochaete chrysosporium metabolized the radiolabeled lignin model compounds [gamma-C]guaiacylglycerol-beta-guaiacyl ether and [4-methoxy-C]veratrylglycerol-beta-guaiacyl ether (VI) to CO(2) in stationary and in shaking cultures. CO(2) evolution was greater in stationary culture. CO(2) evolution from [gamma-C]guaiacyl-glycerol-beta-guaiacyl ether and [4-methoxy-C]veratrylglycerol-beta-guaiacyl ether in stationary cultures was two- to threefold greater when 100% O(2) rather than air (21% O(2)) was the gas phase above the cultures. CO(2) evolution from the metabolism of the substrates occurred only as the culture entered the stationary phase of growth. The presence of substrate levels of nitrogen in the medium suppressed CO(2) evolution from both substrates in stationary cultures. [C]veratryl alcohol and 4-ethoxy-3-methoxybenzyl alcohol were formed as products of the metabolism of VI and 4-ethoxy-3-methoxyphenylglycerol-beta-guaiacyl ether, respectively.

Journal Article↗
PubMed1983

Bacterial methylation of chlorinated phenols and guaiacols: formation of veratroles from guaiacols and high-molecular-weight chlorinated lignin.

Two strains of bacteria, provisionally assigned to the genus Arthrobacter, were shown to metabolize mono-, di-, tri-, and tetrachloroguaiacols and pentachlorophenol to the corresponding O-methyl compounds. Hydroxylated intermediates were formed only transiently, except for the synthesis by one strain of 3,4,5-trichlorosyringol from 3,4,5-trichloroguaiacol. Two isomeric trichloroveratroles and tetrachloroveratrole were formed by three of the strains from a high-molecular-weight chlorinated lignin isolated from kraft pulp mill bleach plant. The concentrations of methylated metabolites varied widely and did not appear to be correlated with degradation. The possible environmental consequences resulting from synthesis of these highly lipophilic substances are discussed briefly.

Journal Article↗
PubMed1984

Degradation of the gamma-Carboxyl-Containing Diarylpropane Lignin Model Compound 3-(4'-Ethoxy-3'-Methoxyphenyl)-2-(4''-Methoxyphenyl)Propionic Acid by the Basidiomycete Phanerochaete chrysosporium.

The white-rot basidiomycete Phanerochaete chrysosporium metabolized 3-(4'-ethoxy-3'-methoxyphenyl)-2-(4''-methoxyphenyl)propionic acid (V) in low-nitrogen, stationary cultures, conditions under which ligninolytic activity is expressed. The ability of several fungal mutant strains to degrade V reflected their ability to degrade [C]lignin to CO(2). 1-(4'-Ethoxy-3'-methoxyphenyl)-2-(4''-methoxyphenyl)-2- hydroxyethane (VII), anisyl alcohol, and 4-ethoxy-3-methoxybenzyl alcohol were isolated as metabolic products, indicating an initial oxidative decarboxylation of V, followed by alpha, beta cleavage of the intermediate (VII). Exogenously added VII was rapidly converted to anisyl alcohol and 4-ethoxy-3-methoxybenzyl alcohol. When the degradation of V was carried out under O(2), O was incorporated into the beta position of the diarylethane product (VII), indicating that the reaction is oxygenative.

Journal Article↗
PubMed1985

Genetic Recombination in the Lignin-Degrading Basidiomycete Phanerochaete chrysosporium.

Heterokaryons made from auxotrophic strains of the lignin-degrading basidiomycete Phanerochaete chrysosporium were induced to fruit. The isolation of wild-type and double-mutant phenotypes from these crosses indicated that genetic recombination had occurred. Cytological studies demonstrated that more than 90% of the basidiospores from the wild-type and auxotrophic strains and from forced heterokaryons were binucleate. Colonies of the wild-type strain of P. chrysosporium arising from single, predominantly uninucleate conidia were all capable of producing fruit bodies and basidiospores.

Journal Article↗
PubMed1985

Production of Ligninases and Degradation of Lignin in Agitated Submerged Cultures of Phanerochaete chrysosporium.

Research on the extracellular hemeprotein ligninases of Phanerochaete chrysosporium has been hampered by the necessity to produce them in stationary culture. This investigation examined the effects of detergents on development of ligninase activity in agitated submerged cultures. Results show that addition of Tween 80, Tween 20, or 3-[(3-colamidopropyl)dimethylammonio]1-propanesulfonate to the cultures permits development of ligninase activity comparable to that routinely obtained in stationary cultures. The detergent-amended cultures express the entire ligninolytic system, assayed as the complete oxidation of [C]lignin to CO(2). The detergent effect is evidently not merely in facilitating release of extant enzyme. Development of ligninolytic activity in the agitated cultures, as in stationary cultures, is idiophasic. Ion-exchange fast protein-liquid chromatography indicated that the heme protein profiles in agitated and stationary cultures are very similar. These findings should make it possible to scale up production of ligninolytic enzymes in stirred tank fermentors.

Journal Article↗
PubMed1987

Metabolism of Lignin Model Compounds of the Arylglycerol-beta-Aryl Ether Type by Pseudomonas acidovorans D(3).

A natural bacterial isolate that we have classified as Pseudomonas acidovorans grows on the lignin model compounds 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol (compound 1) and 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol (compound 1'), as well as on the corresponding 1-oxo compounds (2 and 2') as sole sources of carbon and energy. Metabolic intermediates present in cultures growing on compound 1 included compound 2, 2-methoxyphenol (guaiacol [compound 3]), beta-hydroxypro-pioveratrone (compound 4), acetoveratrone (compound 5), and veratric acid (compound 6). Also identified were compounds 1', 2', beta-hydroxypropiovanillone (compound 4'), and acetovanillone (compound 5'), indicating that 4-O demethylation also occurs. The phenolic intermediates were the same as those found in cultures growing on compound 1'. Compounds 2 and 2' were in part also reduced to compounds 1 and 1', respectively. Compound 3 was shown to be derived from the 2-methoxyphenoxy moiety. A suggested degradation scheme is as follows: compound 1-->2-->(3 + 4)-->5-->6 (and similarly for 1'). In this scheme, the key reaction is cleavage of the ether linkage between C-2 (C(beta)) of the phenylpropane moiety and the 2-methoxyphenoxy moiety in compounds 2 and 2' (i.e., beta-aryl ether cleavage). On the basis of compounds identified, viz., 3 and 4 (4'), cleavage appears formally to be reductive. Because this is unlikely, the initial cleavage products probably were not detected. The implications of these results for the enzyme(s) responsible are discussed.

Journal Article↗
PubMed1988

Degradation of Kraft Indulin Lignin by Streptomyces viridosporus and Streptomyces badius.

Crawford and collaborators have studied extensively the solubilization of lignocellulose by two Streptomyces species, S. badius and S. viridosporus. Using a condensed industrial lignin essentially devoid of carbohydrates, Indulin AT, as the sole source of carbon, similar results were obtained: (i) the growths of the bacteria were optimum at pH 7.5 to 8.5; (ii) yeast extract was a better source of nitrogen than NH(4)Cl; (iii) the products of the depolymerization of Indulin were soluble, acid-precipitable polymers. When d-glucose was added as a secondary carbon source, it was used preferentially and the production of acid-precipitable polymers began only after the complete depletion of the sugar. On the assumption that the degradation of Indulin was catalyzed by enzymes, proteins found in the culture media and soluble and insoluble intracellular proteins were incubated with Indulin at pH 7.0 at 37 degrees C. Proteins in all fractions from S. badius had ligninolytic activities which, with the exception of those in the intracellular soluble fraction, were increased in the presence of H(2)O(2). In S. viridosporus, both extra- and intracellular soluble activities were found which were not increased by H(2)O(2). The extracellular activity of S. viridosporus was not affected by heat, resisted partially an exposure to pH 1.0, and was completely destroyed by proteolysis.

Journal Article↗
PubMed1991

Role of manganese peroxidases and lignin peroxidases of Phanerochaete chrysosporium in the decolorization of kraft bleach plant effluent.

The role of lignin peroxidases (LIPs) and manganese peroxidases (MNPs) of Phanerochaete chrysosporium in decolorizing kraft bleach plant effluent (BPE) was investigated. Negligible BPE decolorization was exhibited by a per mutant, which lacks the ability to produce both the LIPs and the MNPs. Also, little decolorization was seen when the wild type was grown in high-nitrogen medium, in which the production of LIPs and MNPs is blocked. A lip mutant of P. chrysosporium, which produces MNPs but not LIPs, showed about 80% of the activity exhibited by the wild type, indicating that the MNPs play an important role in BPE decolorization. When P. chrysosporium was grown in a medium with 100 ppm of Mn(II), high levels of MNPs but no LIPs were produced, and this culture also exhibited high rates of BPE decolorization, lending further support to the idea that MNPs play a key role in BPE decolorization. When P. chrysosporium was grown in a medium with no Mn(II), high levels of LIPs but negligible levels of MNPs were produced and the rate and extent of BPE decolorization by such cultures were quite low, indicating that LIPs play a relatively minor role in BPE decolorization. Furthermore, high rates of BPE decolorization were seen on days 3 and 4 of incubation, when the cultures exhibit high levels of MNP activity but little or no LIP activity. These results indicate that MNPs play a relatively more important role than LIPs in BPE decolorization by P. chrysosporium.

Basidiomycota↗
PubMed1993

Temporal expression of the major lignin peroxidase genes of Phanerochaete chrysosporium.

DNA probes specific for the genes encoding major lignin peroxidase (LIP) isozymes H2, H8, and H10 of Phanerochaete chrysosporium were constructed. These probes were used to study the temporal expression of the three lip genes in defined low-nitrogen medium. H2 gene transcripts were produced at high levels on days 4, 5, and 7 and at low levels on day 6, while the H8 gene transcripts peaked on day 4 and were produced in substantially lower amounts thereafter. H10 transcripts, on the other hand, peaked on day 4, dropped precipitously on day 5, and were barely detectable on days 6 and 7. There was no precise correlation between lip transcript and isozyme levels.

Base Sequence↗