Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.10.3.2 (laccase)
 4,656 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Extracellular manganese peroxidase and laccase activities were detected in cultures of Dichomitus squalens (Polyporus anceps) under conditions favoring lignin degradation. In contrast, neither extracellular lignin peroxidase nor aryl alcohol oxidase activity was detected in cultures grown under a wide variety of conditions. The mineralization of 14C-ring-, -side chain-, and -methoxy-labeled synthetic guaiacyl lignins by D. squalens and the expression of extracellular manganese peroxidase were dependent on the presence of Mn(II), suggesting that manganese peroxidase is an important component of this organism's lignin degradation system. The expression of laccase activity was independent of manganese. In contrast to previous findings with Phanerochaete chrysosporium, lignin degradation by D. squalens proceeded in the cultures containing excess carbon and nitrogen.
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PMID:Manganese regulation of manganese peroxidase expression and lignin degradation by the white rot fungus Dichomitus squalens. 176 94

Lignin peroxidase oxidizes non-phenolic substrates by one electron to give aryl-cation-radical intermediates, which react further to give a variety of products. The present study investigated the possibility that other peroxidative and oxidative enzymes known to catalyse one-electron oxidations may also oxidize non-phenolics to cation-radical intermediates and that this ability is related to the redox potential of the substrate. Lignin peroxidase from the fungus Phanerochaete chrysosporium, horseradish peroxidase (HRP) and laccase from the fungus Trametes versicolor were chosen for investigation with methoxybenzenes as a homologous series of substrates. The twelve methoxybenzene congeners have known half-wave potentials that differ by as much as approximately 1 V. Lignin peroxidase oxidized the ten with the lowest half-wave potentials, whereas HRP oxidized the four lowest and laccase oxidized only 1,2,4,5-tetramethoxybenzene, the lowest. E.s.r. spectroscopy showed that this congener is oxidized to its cation radical by all three enzymes. Oxidation in each case gave the same products: 2,5-dimethoxy-p-benzoquinone and 4,5-dimethoxy-o-benzoquinone, in a 4:1 ratio, plus 2 mol of methanol for each 1 mol of substrate. Using HRP-catalysed oxidation, we showed that the quinone oxygen atoms are derived from water. We conclude that the three enzymes affect their substrates similarly, and that whether an aromatic compound is a substrate depends in large part on its redox potential. Furthermore, oxidized lignin peroxidase is clearly a stronger oxidant than oxidized HRP or laccase. Determination of the enzyme kinetic parameters for the methoxybenzene oxidations demonstrated further differences among the enzymes.
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PMID:Comparison of lignin peroxidase, horseradish peroxidase and laccase in the oxidation of methoxybenzenes. 216 14

One oxidase (EC 1.10.3.2) and three lignin peroxidases (EC 1.11.1.-) were purified from the culture liquid of the white-rot fungus Phlebia radiata Fr. All the enzymes were glycoproteins. The oxidase had Mr 64,000 and the lignin peroxidases I, II and III had Mr values 42,000, 45,000 and 44,000 respectively. The lignin peroxidases were found to share common antigenic determinants: lignin peroxidases II and III were serologically indistinguishable and lignin peroxidase I was related but distinguishable. The oxidase did not share any immunological properties with the lignin peroxidases. Lignin peroxidases of Phlebia contain protoporphyrin IX as a prosthetic group. In the presence of H2O2 and an electron donor, veratryl alcohol, lignin peroxidases exhibit spectral shifts analogous to those of animal catalase (EC 1.11.1.6). Phlebia enzymes show optimal activity at pH 3-4.5 at 40 degrees C and are stable in the pH range 5-6. They modify Kraft lignin and phenolic compounds containing hydroxy and methoxy groups.
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PMID:Ligninolytic enzymes of the white-rot fungus Phlebia radiata. 319 1

Biobleaching of hardwood unbleached kraft pulp (UKP) by Phanerochaete chrysosporium and Trametes versicolor was studied in the solid-state fermentation system with different culture media. In this fermentation system with low-nitrogen and high-carbon culture medium, pulp brightness increased by 15 and 30 points after 5 days of treatment with T. versicolor and P. chrysosporium, respectively, and the pulp kappa number decreased with increasing brightness. A comparison of manganese peroxidase (MnP), lignin peroxidase (LiP), and laccase activities assayed by using fungus-treated pulp and the filtrate after homogenizing the fungus-treated pulp in buffer solution indicated that enzymes secreted from fungi were adsorbed onto the UKP and that assays of these enzyme activities should be carried out with the treated pulp. Time course studies of brightness increase and MnP activity during treatment with P. chrysosporium suggested that it was difficult to correlate them on the basis of data obtained on a certain day of incubation, because the MnP activity fluctuated dramatically during the treatment time. When brightness increase and cumulative MnP, LiP, and laccase activities were determined, a linear relationship between brightness increase and cumulative MnP activity was found in the solid-state fermentation system with both P. chrysosporium and T. versicolor. This result suggests that MnP is involved in brightening of UKP by white rot fungi.
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PMID:Correlation of brightening with cumulative enzyme activity related to lignin biodegradation during biobleaching of kraft pulp by white rot fungi in the solid-state fermentation system. 757

A bleachery effluent from a sulfite process pulp mill, which was extracted with alkali and treated with oxygen and hydrogen peroxide (EOP), was treated with two fungi, Trametes versicolor and Stagonospora gigaspora. Trametes versicolor did not cause any depolymerization or degradation of effluent lignins but increased the amount of chromophores, whereas S. gigaspora depolymerized the EOP lignins and caused a substantial reduction in aromatic compounds. For both fungal treatments, CuO oxidation caused a decrease in the yield of the aldehydes within the vanillyl and p-hydroxy phenol families, which was faster than the rates of decrease in the yields of the corresponding acids and ketones. However, only S. gigaspora caused changes in the pattern of the 11 characteristic lignin phenols produced by CuO oxidation, reflecting a preferential metabolism of some phenolic precursors. This fungus decreased the yield of total vanillyl phenols (V), which contributed the bulk of the 11 lignin oxidation products, from 93% initially to 59%. As a consequence, coumaryl (C), syringyl (S), and p-hydroxy phenols (P) became relatively enriched to 1.2, 6.5, and 33%, respectively. The stability of EOP-lignin constituent subunits is S > P > C > V. The two fungi differed significantly in their level of enzyme activities. In effluent-free medium, the ratio of laccase to peroxidase was higher for T. versicolor than for S. gigaspora. The presence of EOP-lignins significantly increased this ratio. No lignin peroxidase was detected but manganese peroxidase and laccase were detected during degradation activities.
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PMID:Degradability of chlorine-free bleachery effluent lignins by two fungi: effects on lignin subunit type and on polymer molecular weight. 801 7

Oxidation capacities of laccase, manganese peroxidase (MnP) and lignin peroxidase (LiP) from Phlebia radiata were compared using non-phenolic (veratryl alcohol and ABTS) and phenolic (syringaldazine, vanillalacetone and Phenol red) compounds as reducing substrates. The effect of Mn(II) on enzyme reactions was also studied. Highest specific activities were recorded with laccase in the oxidation of phenolic compounds or ABTS and irrespective of Mn(II) concentration. LiP and MnP oxidized all these substrates but only the catalysis of MnP was dependent upon Mn(II). Only LiP clearly oxidized veratryl alcohol. However, Mn(II) interfered with this reaction by repressing veratraldehyde formation. These results point to multiple participation of manganese ions, either as a reducing (Mn(II)) or oxidizing (Mn(III)) agent in the enzymatic reactions.
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PMID:Participation of Mn(II) in the catalysis of laccase, manganese peroxidase and lignin peroxidase from Phelbia radiata. 803 57

This method was proposed earlier for measuring glucose in a peroxidase-glucose oxidase system but has not been studied for determination of manganese peroxidase (MnP) activity. The assay is based on the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) and 3-(dimethylamino)benzoic acid (DMAB). The reaction of MBTH and DMAB in the presence of H2O2, Mn2+, and MnP gives a deep purple-blue color with a broad absorption band with a peak at 590 nm. The extinction coefficient is high (53,000 M-1 cm-1), so low MnP activities can be detected. Lignin peroxidase and laccase, usually present in cultures of white rot fungi, gave little or no interference at the concentrations tested. However, slight interference from very high LiP activity may occur at very low MnP activity.
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PMID:Determination of manganese peroxidase activity with 3-methyl-2-benzothiazolinone hydrazone and 3-(dimethylamino)benzoic acid. 807 99

Phanerochaete chrysosporium is rapidly becoming a model system for the study of lignin biodegradation. Numerous studies on the physiology, biochemistry, chemistry, and genetics of this system have been performed. However, P. chrysosporium is not the only fungus to have a lignin-degrading enzyme system. Many other ligninolytic species of fungi, as well as other distantly related organisms which are known to produce lignin peroxidases, are described in this paper. In this study, we demonstrated the presence of the peroxidative enzymes in nine species not previously investigated. The fungi studied produced significant manganese peroxidase activity when they were grown on an oak sawdust substrate supplemented with wheat bran, millet, and sucrose. Many of the fungi also exhibited laccase and/or glyoxal oxidase activity. Inhibitors present in the medium prevented measurement of lignin peroxidase activity. However, Western blots (immunoblots) revealed that several of the fungi produced lignin peroxidase proteins. We concluded from this work that lignin-degrading peroxidases are present in nearly all ligninolytic fungi, but may be expressed differentially in different species. Substantial variability exists in the levels and types of ligninolytic enzymes produced by different white not fungi.
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PMID:Ubiquity of lignin-degrading peroxidases among various wood-degrading fungi. 828 5

The ability of Phanerochaete laevis HHB-1625 to transform polycyclic aromatic hydrocarbons (PAHs) in liquid culture was studied in relation to its complement of extracellular ligninolytic enzymes. In nitrogen-limited liquid medium, P. laevis produced high levels of manganese peroxidase (MnP). MnP activity was strongly regulated by the amount of Mn2+ in the culture medium, as has been previously shown for several other white rot species. Low levels of laccase were also detected. No lignin peroxidase (LiP) was found in the culture medium, either by spectrophotometric assay or by Western blotting (immunoblotting). Despite the apparent reliance of the strain primarily on MnP, liquid cultures of P. laevis were capable of extensive transformation of anthracene, phenanthrene, benz[a]anthracene, and benzo[a]pyrene. Crude extracellular peroxidases from P. laevis transformed all of the above PAHs, either in MnP-Mn2+ reactions or in MnP-based lipid peroxidation systems. In contrast to previously published studies with Phanerochaete chrysosporium, metabolism of each of the four PAHs yielded predominantly polar products, with no significant accumulation of quinones. Further studies with benz[a]anthracene and its 7,12-dione indicated that only small amounts of quinone products were ever present in P. laevis cultures and that quinone intermediates of PAH metabolism were degraded faster and more extensively by P. laevis than by P. chrysosporium.
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PMID:Polycyclic aromatic hydrocarbon-degrading capabilities of Phanerochaete laevis HHB-1625 and its extracellular ligninolytic enzymes. 863 57

Lignin peroxidase is generally considered to be a primary catalyst for oxidative depolymerization of lignin by white-rot fungi. However, some white-rot fungi lack lignin peroxidase. Instead, many produce laccase, even though the redox potentials of known laccases are too low to directly oxidize the non-phenolic components of lignin. Pycnoporus cinnabarinus is one example of a laccase-producing fungus that degrades lignin very efficiently. To overcome the redox potential barrier, P. cinnabarinus produces a metabolite, 3-hydroxyanthranilate that can mediate the oxidation of how non-phenolic substrates by laccase. This is the first description of how laccase might function in a biological system for the complete depolymerization of lignin.
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PMID:A fungal metabolite mediates degradation of non-phenolic lignin structures and synthetic lignin by laccase. 870 3


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