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:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1H NMR spectra at 200- and 600-MHz of manganese peroxidase from Phanerochaete chrysosporium and of its cyanide derivative are reported. The spectrum of the native protein is very similar to that of other peroxidases. The assignment of the spectrum of the cyanide derivative has been performed through 1D NOE, 2D NOESY, and COSY experiments. This protein is very similar to lignin peroxidase, the only meaningful difference being the shift of H delta 2 of the proximal histidine. The spectra of the cyanide derivative of these two proteins are compared with those of horseradish peroxidase and cytochrome c peroxidase. The shift pattern of the protons of the proximal histidine is discussed relative to the structural properties which affect the Fe3+/Fe2+ redox potential.
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PMID:1H NMR investigation of manganese peroxidase from Phanerochaete chrysosporium. A comparison with other peroxidases. 132 29

Manganese oxidation by manganese peroxidase (MnP) was investigated. Stoichiometric, kinetic, and MnII binding studies demonstrated that MnP has a single manganese binding site near the heme, and two MnIII equivalents are formed at the expense of one H2O2 equivalent. Since each catalytic cycle step is irreversible, the data fit a peroxidase ping-pong mechanism rather than an ordered bi-bi ping-pong mechanism. MnIII-organic acid complexes oxidize terminal phenolic substrates in a second-order reaction. MnIII-lactate and -tartrate also react slowly with H2O2, with third-order kinetics. The latter slow reaction does not interfere with the rapid MnP oxidation of phenols. Oxalate and malonate are the only organic acid chelators secreted by the fungus in significant amounts. No relationship between stimulation of enzyme activity and chelator size was found, suggesting that the substrate is free MnII rather than a MnII-chelator complex. The enzyme competes with chelators for free MnII. Optimal chelators, such as malonate, facilitate MnIII dissociation from the enzyme, stabilize MnIII in aqueous solution, and have a relatively low MnII binding constant.
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PMID:Manganese(II) oxidation by manganese peroxidase from the basidiomycete Phanerochaete chrysosporium. Kinetic mechanism and role of chelators. 142 9

Under ligninolytic conditions, the white rot basidiomycete Phanerochaete chrysosporium mineralizes 2,4-dinitrotoluene (I). The pathway for the degradation of I was elucidated by the characterization of fungal metabolites and oxidation products generated by lignin peroxidase (LiP), manganese peroxidase (MnP), and crude intracellular cell extracts. The multistep pathway involves the initial reduction of I to yield 2-amino-4-nitrotoluene (II). II is oxidized by MnP to yield 4-nitro-1,2-benzoquinone (XII) and methanol. XII is then reduced to 4-nitro-1,2-hydroquinone (V), and the latter is methylated to 1,2-dimethoxy-4-nitrobenzene (X). 4-Nitro-1,2-hydroquinone (V) is also oxidized by MnP to yield nitrite and 2-hydroxybenzoquinone, which is reduced to form 1,2,4-trihydroxybenzene (VII). 1,2-Dimethoxy-4-nitrobenzene (X) is oxidized by LiP to yield nitrite, methanol, and 2-methoxy-1,4-benzoquinone (VI), which is reduced to form 2-methoxy-1,4-hydroquinone (IX). The latter is oxidized by LiP and MnP to 4-hydroxy-1,2-benzoquinone, which is reduced to 1,2,4-trihydroxybenzene (VII). The key intermediate 1,2,4-trihydroxybenzene is ring cleaved by intracellular cell extracts to produce, after reduction, beta-ketoadipic acid. In this pathway, initial reduction of a nitroaromatic group generates the peroxidase substrate II. Oxidation of II releases methanol and generates 4-nitro-1,2-benzoquinone (XII), which is recycled by reduction and methylation reactions to regenerate intermediates which are in turn substrates for peroxidase-catalyzed oxidation leading to removal of the second nitro group. Thus, this unique pathway apparently results in the removal of both aromatic nitro groups before ring cleavage takes place.
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PMID:Degradation of 2,4-dinitrotoluene by the lignin-degrading fungus Phanerochaete chrysosporium. 153 77

Under secondary metabolic conditions, the white-rot basidiomycete Phanerochaete chrysosporium degraded 2,7-dichlorodibenzo-p-dioxin (I). The pathway for the degradation of I was elucidated by the characterization of fungal metabolites and oxidation products generated by lignin peroxidase (LiP), manganese peroxidase (MnP), and crude intracellular cell-free extracts. The multistep pathway involves the degradation of I and subsequent intermediates by oxidation, reduction, and methylation reactions to yield the key intermediate 1,2,4-trihydroxybenzene (III). In the first step, the oxidative cleavage of the dioxin ring of I, catalyzed by LiP, generates 4-chloro-1,2-benzoquinone (V), 2-hydroxy-1,4-benzoquinone (VIII), and chloride. The intermediate V is then reduced to 1-chloro-3,4-dihydroxybenzene (II), and the latter is methylated to form 1-chloro-3,4-dimethoxybenzene (VI). VI in turn is oxidized by LiP to generate chloride and 2-methoxy-1,4-benzoquinone (VII), which is reduced to 2-methoxy-1,4-dihydroxybenzene (IV). IV is oxidized by either LiP or MnP to generate 4-hydroxy-1,2-benzoquinone, which is reduced to 1,2,4-trihydroxybenzene (III). The other aromatic product generated by the initial LiP-catalyzed cleavage of I is 2-hydroxy-1,4-benzoquinone (VIII). This intermediate is also generated during the LiP- or MnP-catalyzed oxidation of the intermediate chlorocatechol (II). VIII is also reduced to 1,2,4-trihydroxybenzene (III). The key intermediate III is ring cleaved by intracellular cell extracts to produce, after reduction, beta-ketoadipic acid. In this pathway, initial oxidative cleavage of both C-O-C bonds in I by LiP generates two quinone products, 4-chloro-1,2-benzoquinone (V) and 2-hydroxy-1,4-benzoquinone (VIII). The former is recycled by reduction and methylation reactions to generate an intermediate which is also a substrate for peroxidase-catalyzed oxidation, leading to the removal of a second chlorine atom. This unique pathway results in the removal of both aromatic chlorines before aromatic ring cleavage takes place.
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PMID:Degradation of 2,7-dichlorodibenzo-p-dioxin by the lignin-degrading basidiomycete Phanerochaete chrysosporium. 155 37

The structures of the active sites of horseradish and cytochrome c peroxidase, prototypical peroxidases with an imidazole heme ligand, suggest that small substrates are generally oxidized by peroxidases at the delta-meso edge of the heme group. This inference is supported by experimental results on the Coprinus macrorhizus peroxidase (52), manganese peroxidase (51), lignin peroxidase (50) and, less definitively, lactoperoxidase (90). Macromolecular substrates, exemplified by the cytochrome c peroxidase-cytochrome c interaction, are likely to be oxidized at peroxidase surface sites bearing no specific relationship to the delta-meso heme edge. The second oxidation equivalent in the two-electron Compound I states of the peroxidases is stored either as a porphyrin radical or as a protein radical, although some peroxidases have both types of compound I. The factors that control the location of the second oxidation equivalent remain unclear. Classical peroxidases do not generally catalyze olefin epoxidation and other monooxygenations but do catalyze sulfoxidation reactions. This is best rationalized by physical separation of the substrate from the ferryl oxygen, possibly by a protein barrier, because results with cytochrome c peroxidase show that there is no inherent mechanistic reason for the inability of peroxidases to epoxidize olefins. It is not yet clear why the barrier to oxygen transfer reactions is circumvented during sulfur oxidation reactions, although one possibility is that the relatively stable sulfur cation radical that is initially formed disrupts the barrier. Chloroperoxidase, the principal nonclassical hemoprotein peroxidase so far examined, has an open active site that readily catalyzes P450-like monooxygenation reactions. The active site of chloroperoxidase is a potentially useful model for that of myeloperoxidase, but caution must be used in extrapolating from one to the other because myeloperoxidase has a histidine rather than thiolate fifth heme ligand and therefore is a classical rather than nonclassical peroxidase.
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PMID:Catalytic sites of hemoprotein peroxidases. 160 82

Phanerochaete chrysosporium is a white rot fungus which secretes a family of lignin-degrading enzymes under nutrient limitation. PSBL-1 is a mutant of this organism that generates the ligninolytic system under nonlimiting conditions during primary metabolism. Lignin peroxidase, manganese peroxidase, and glyoxal oxidase activities for PSBL-1 under nonlimiting conditions were 4- to 10-fold higher than those of the wild type (WT) under nitrogen-limiting conditions. PSBL-1 was still in the log phase of growth while secreting the enzymes, whereas the WT had ceased to grow by this time. As in the WT, manganese(II) increased manganese peroxidase activity in the mutant. However, manganese also caused an increase in lignin peroxidase and glyoxal oxidase activities in PSBL-1. Addition of veratryl alcohol to the culture medium stimulated lignin peroxidase activity, inhibited glyoxal oxidase activity, and had little effect on manganese peroxidase activity in PSBL-1, as in the WT. Fast protein liquid chromatography (FPLC) analysis shows production of larger amounts of isozyme H2 in PSBL-1 than in the WT. These properties make PSBL-1 very useful for isolation of large amounts of all ligninolytic enzymes for biochemical study, and they open the possibility of scale-up production for pratical use.
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PMID:Overproduction of lignin-degrading enzymes by an isolate of Phanerochaete chrysosporium. 176 32

Phanerochaete chrysosporium was able to degrade high molecular weight chlorolignins (Mr greater than 30,000) from bleach plant effluents, although a direct contact between ligninolytic enzymes and chlorolignin was prevented by a dialysis tubing. In the absence of the enzymes, Mn3+ depolymerized chlorolignin when complexed with lactate causing the color, chemical oxygen demand (COD) and dry weight to decrease by 80%, 60% and 40%, respectively. Manganese peroxidase effectively catalyzed the depolymerization of chlorolignin in the presence of Mn2+ and H2O2. It can be concluded from these results that manganese peroxidase plays the major role in the initial breakdown and decolorization of high molecular weight chlorolignin in bleach plant effluents by P. chrysosporium in vivo.
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PMID:Oxidative degradation of high molecular weight chlorolignin by manganese peroxidase of Phanerochaete chrysosporium. 187 32

Manganese peroxidase, produced by some white-rot fungi during lignin degradation, catalyzes the oxidation of Mn2+ to Mn3+. Whereas Mn3+ is known to oxidize phenolic compounds, its role in lignin degradation is not clear. We have used a series of methoxybenzenes with E1/2 values of 1.76-0.81 V (vs saturated calomel electrode) to investigate the oxidizing ability of Mn3+ chelates generated chemically and enzymatically. Although lignin peroxidase has been shown to oxidize high potential congeners, our results show that manganese peroxidase, or physiological concentrations of Mn3+, oxidize only the lower potential congeners. In addition, Mn3+ increased the rate of decay of the cation radical of 1,2,4,5-tetramethoxybenzene. The kinetics of decay continued to be first order, so Mn3+ does not oxidize the cation radical itself, but probably oxidizes a neutral dienyl radical derived from the cation radical. This indicates a possible role for Mn3+ in lignin degradation, as neutral dienyl radicals are proposed to be products of lignin peroxidase action.
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PMID:Oxidation of methoxybenzenes by manganese peroxidase and by Mn3+. 189 12

Under secondary metabolic conditions the white rot basidiomycete Phanerochaete chrysosporium mineralizes 2,4-dichlorophenol (I). The pathway for the degradation of 2,4-dichlorophenol (I) was elucidated by the characterization of fungal metabolites and of oxidation products generated by purified lignin peroxidase and manganese peroxidase. The multistep pathway involves the oxidative dechlorination of 2,4-dichlorophenol (I) to yield 1,2,4,5-tetrahydroxybenzene (VIII). The intermediate 1,2,4,5-tetrahydroxybenzene (VIII) is ring cleaved to produce, after subsequent oxidation, malonic acid. In the first step of the pathway, 2,4-dichlorophenol (I) is oxidized to 2-chloro-1,4-benzoquinone (II) by either manganese peroxidase or lignin peroxidase. 2-Chloro-1,4-benzoquinone (II) is then reduced to 2-chloro-1,4-hydroquinone (III), and the latter is methylated to form the lignin peroxidase substrate 2-chloro-1,4-dimethoxybenzene (IV). 2-Chloro-1,4-dimethoxybenzene (IV) is oxidized by lignin peroxidase to generate 2,5-dimethoxy-1,4-benzoquinone (V), which is reduced to 2,5-dimethoxy-1,4-hydroquinone (VI). 2,5-Dimethoxy-1,4-hydroquinone (VI) is oxidized by either peroxidase to generate 2,5-dihydroxy-1,4-benzoquinone (VII) which is reduced to form the tetrahydroxy intermediate 1,2,4,5-tetrahydroxybenzene (VIII). In this pathway, the substrate is oxidatively dechlorinated by lignin peroxidase or manganese peroxidase in a reaction which produces a p-quinone. The p-quinone intermediate is then recycled by reduction and methylation reactions to regenerate an intermediate which is again a substrate for peroxidase-catalyzed oxidative dechlorination. This unique pathway apparently results in the removal of both chlorine atoms before ring cleavage occurs.
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PMID:Degradation of 2,4-dichlorophenol by the lignin-degrading fungus Phanerochaete chrysosporium. 198 25

The expression of manganese peroxidase in nitrogen-limited cultures of Phanerochaete chrysosporium is dependent on Mn, and initial work suggested that Mn regulates transcription of the mnp gene. In this study, using Northern (RNA) blot analysis of kinetic, dose-response, and inhibitor experiments, we demonstrate unequivocally that Mn regulates mnp gene transcription. The amount of mnp mRNA in cells of 4-day-old nitrogen-limited cultures is a direct function of the concentration of Mn in the culture medium up to a maximum of 180 microM. Addition of Mn to nitrogen-limited Mn-deficient secondary metabolic (4-, 5-, and 6-day-old) cultures results in the appearance of mnp mRNA within 40 min. The appearance of this message is completely inhibited by the RNA synthesis inhibitor dactinomycin but not by the protein synthesis inhibitor cycloheximide. Furthermore, the amount of mnp mRNA produced is a direct function of the concentration of added Mn. In contrast, addition of Mn to low-nitrogen Mn-deficient 2- or 3-day-old cultures does not result in the appearance of mnp mRNA. Manganese peroxidase protein is detected by specific immunoprecipitation of the in vitro translation products of poly(A) RNA isolated from Mn-supplemented (but not from Mn-deficient) cells. All of these results demonstrate that Mn, the substrate for the enzyme, regulates mnp gene transcription via a growth-stage-specific and concentration-dependent mechanism.
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PMID:Manganese peroxidase gene transcription in Phanerochaete chrysosporium: activation by manganese. 206 Dec 89


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