Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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

Laccase is one of the ligninolytic enzymes found in liquid cultures of the fungus Ceriporiopsis subvermispora in defined medium. As an approach to a clarification of the role of laccases during the attack on lignin by the fungus, the enzyme has been characterized further. The levels of this phenol oxidase increase 2-fold in the presence of p-anisidine and are severely affected when addition of either Mn(II) or Cu(II) ions to the medium is omitted. Isoelectrofocusing allowed the resolution of two laccase isoenzymes, with pIs of 3.65 and 3.59. In rich medium, laccase activity is 10-fold higher than in salt medium, and it is not affected by the external addition of p-anisidine or Mn(II). Four isoenzymes were detected in these cultures, with pIs between 3.76 and 3.60. In a wheat bran medium, four isoenzymes with pIs in the range 3.63-3.46, plus a fifth isoenzyme of high pI (4.82), were also identified. The absorption spectrum of a pool containing the four isoenzymes from rich medium shows a maximum at 600 nm, typical of laccase possessing a type I copper atom. The molecular mass of the isoenzyme with pI 3.60 is 79 kDa, as determined by SDS/PAGE. Upon treatment with endoglycosidase F, the molecular mass of this isoform decreases to 63 kDa, indicating a high degree of glycosylation. Substrate specificity studies conducted with the four isoenzymes from rich medium and a combination of isoenzymes from salt medium showed marked differences among them. The amino-terminal sequences (24 residues) of three isoenzymes isolated from rich medium were determined. Two of them are identical, whereas the third one differs from these in three amino acid residues. The consensus sequence reveals clear homology with laccases from other microorganisms.
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PMID:Properties of laccase isoenzymes produced by the basidiomycete Ceriporiopsis subvermispora. 779 34

The white-rot basidiomycete Ceriporiopsis subvermispora produces two families of ligninolytic enzymes, namely manganese-dependent peroxidases (MnPs) and laccases, when growing in liquid cultures of defined composition. In medium containing 11 p.p.m. of Mn(II), up to seven isoenzymes of MnP and four isoenzymes of laccase were resolved by isoelectrofocusing (IEF), with pI values in the range 4.10-4.60 and 3.45-3.65, respectively. Occasionally, a fifth laccase isoform of pI 4.70 was also detected. In cultures with 25 and 40 p.p.m. of Mn(II), mainly the MnPs with higher pI values are produced. The isoenzyme pattern of MnP is not altered throughout the growth period of the fungus. MnP and laccase are also produced by C. subvermispora when growing on wood chips of Pinus radiata. Highest levels of both enzymes were obtained during the first week of incubation. A second peak of MnP activity was observed during the fourth week, whereas very low levels of laccase were extracted from the chips after the second week of growth. IEF analysis showed that the pI values of these laccases are similar to those of laccases produced in liquid cultures, being in the range 3.45-3.65. In contrast, four isoforms of MnP were resolved during the first week of incubation on wood chips, with pI values of 4.40, 4.17, 4.04 and 3.53. This profile underwent a transition during the second week of growth, at the end of which isoforms of MnP with pI values of 3.53, 3.40, 3.30 and 3.20 were resolved by IEF.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Isoenzymes of manganese-dependent peroxidase and laccase produced by the lignin-degrading basidiomycete Ceriporiopsis subvermispora. 800 May 40

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

The ligninolytic enzymes produced by the white rot fungus Phanerochaete sordida in liquid culture were studied. Only manganese peroxidase (MnP) activity could be detected in the supernatant liquid of the cultures. Lignin peroxidase (LiP) and laccase activities were not detected under a variety of different culture conditions. The highest MnP activity levels were obtained in nitrogen-limited cultures grown under an oxygen atmosphere. The enzyme was induced by Mn(II). The initial pH of the culture medium did not significantly affect the MnP production. Three MnP isozymes were identified (MnPI, MnPII, and MnPIII) and purified to homogeneity by anion-exchange chromatography followed by hydrophobic chromatography. The isozymes are glycoproteins with approximately the same molecular mass (around 45 kDa) but have different pIs. The pIs are 5.3, 4.2, and 3.3 for MnPI, MnPII, and MnPIII, respectively. The three isozymes are active in the same range of pHs (pHs 3.0 to 6.0) and have optimal pHs between 4.5 and 5.0. Their amino-terminal sequences, although highly similar, were distinct, suggesting that each is the product of a separate gene.
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PMID:Manganese peroxidases of the white rot fungus Phanerochaete sordida. 813 19

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

The white rot fungus Pycnoporus cinnabarinus was characterized with respect to its set of extracellular phenoloxidases. Laccase was produced as the predominant extracellular phenoloxidase in conjunction with low amounts of an unusual peroxidase. Neither lignin peroxidase nor manganese peroxidase was detected. Laccase was produced constitutively during primary metabolism. Addition of the most effective inducer, 2,5-xylidine, enhanced laccase production ninefold without altering the isoenzyme pattern of the enzyme. Laccase purified to apparent homogeneity was a single polypeptide having a molecular mass of approximately 81,000 Da, as determined by calibrated gel filtration chromatography, and a carbohydrate content of 9%. The enzyme displayed an unusual behavior on isoelectric focusing gels; the activity was split into one major band (pI, 3.7) and several minor bands of decreasing intensity which appeared at regular, closely spaced intervals toward the alkaline end of the gel. Repeated electrophoresis of the major band under identical conditions produced the same pattern, suggesting that the laccase was secreted as a single acidic isoform with a pI of about 3.7 and that the multiband pattern was an artifact produced by electrophoresis. This appeared to be confirmed by N-terminal amino acid sequencing of the purified enzyme, which yielded a single sequence for the first 21 residues. Spectroscopic analysis indicated a typical laccase active site in the P. cinnabarinus enzyme since all three typical Cu(II)-type centers were identified. Substrate specificity and inhibitor studies also indicated the enzyme to be a typical fungal laccase. The N-terminal amino acid sequence of the P. cinnabarinus laccase showed close homology to the N-terminal sequences determined for laccases from Trametes versicolor, Coriolus hirsutus, and an unidentified basidiomycete, PM1. The principal features of the P. cinnabarinus enzyme system, a single predominant laccase and a lack of lignin- or manganese-type peroxidase, make this organism an interesting model for further studies of possible alternative pathways of lignin degradation by white rot fungi.
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PMID:The ligninolytic system of the white rot fungus Pycnoporus cinnabarinus: purification and characterization of the laccase. 891 75

Quinone redox cycling is generally known as an intracellular process that implies the reduction of quinones (Q) into semiquinones (Q-.) or hydroquinones (QH2), which autoxidize reducing oxygen to superoxide anion radical (O-.2). We demonstrate here for the first time the existence of quinone redox cycling in a ligninolytic fungus, Pleurotus eryngii, showing two particularities: extracellular production of O-.2 and involvement of ligninolytic enzymes. Experiments were performed with P. eryngii cultures, showing laccase activity, and four quinones: 1,4-benzoquinone (BQ), 2-methyl-1,4-benzoquinone (MeBQ), 2,3,5,6-tetramethyl-1,4-benzoquinone (duroquinone, DQ), and 2-methyl-1,4-naphthoquinone (menadione, MD). The overall process consisted of cell-bound divalent reduction of quinones, followed by extracellular laccase-mediated oxidation of hydroquinones into semiquinones, which autoxidized to a certain extent producing O-.2 (at the pH values of natural degradation of lignin, some autoxidation of hydroquinones was observed only with DQH2 and MDH2). The existence of a redox cyclic system involving quinones was evidenced by determining the chemical state of quinones along incubation under several conditions (either different O2 concentrations and pH values or laccase amounts). Thus, QH2/Q ratios at system equilibrium decreased as either pH values and oxygen concentration (allowing hydroquinones autoxidation) or the amount of laccase increased. Once the cyclic nature of the system was demonstrated, special attention was paid to the production of O-.2 during hydroquinone oxidation. Except in the case of BQH2, production of O-.2 was found in samples containing hydroquinones and laccase. By the use of agents promoting the autoxidation of semiquinones (superoxide dismutase and Mn2+), production of O-.2 during oxidation of BQH2 could finally be demonstrated.
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PMID:Quinone redox cycling in the ligninolytic fungus Pleurotus eryngii leading to extracellular production of superoxide anion radical. 905 49

Phenanthrene, a polycyclic aromatic hydrocarbon, was efficiently oxidized by laccase in the presence of both 1-hydroxybenzotriazole and unsaturated lipids. 73% of initially added phenanthrene was degraded within 182 hours to give phenanthrene-9,10-quinone and 2,2'-diphenic acid as the major products. The system was also able to peroxidize linoleic acid to its corresponding hydroperoxides suggesting the involvement of lipid peroxidation in laccase catalyzed phenanthrene oxidation. Lipid peroxidation by laccase required 1-hydroxybenzotriazole and did not depend on Mn2+ and H2O2 suggesting that the chemical reactions involved differ from those previously reported for manganese peroxidase.
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PMID:Oxidation of phenanthrene by a fungal laccase in the presence of 1-hydroxybenzotriazole and unsaturated lipids. 951 95


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