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)

Monophenol monooxygenase (monophenol, dihydroxyphenylalanine:oxygen oxidoreductase EC 1.14.18.1) was studied in melanin-positive and melanin-negative mutants of Streptomyces lincolnensis NCIB 9413, varying in the lincomycin synthesizing ability. The activities of laccase and tyrosine phenol lyase (EC 4.1.99.2) are absent in this organism. The monophenol monooxygenase catalyzes hydroxylation of monophenols (K(m) and V(max) for l-tyrosine, 2 x 10(-4) M and 8.0 nmol of O(2)/min per ml, respectively) at a slower rate than it dehydrogenates diphenols to o-quinones (K(m) and V(max) for l-3,4-dihydroxyphenylalanine, 7 x 10(-5) M and 51.7 nmol of O(2)/min per ml, respectively. It is inhibited by KCN, beta-mercaptoethanol, ethylenediaminetetraacetate, dipyridyl, thiourea, p-aminobenzoic acids and by some tryptophan metabolites. Changes in the activity of monophenol monooxygenase caused by mutation or by inhibitors are reflected in the synthesis of the antibiotic. Its participation in the biogenesis of the propylhygric moiety of lincomycin is discussed.
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PMID:Monophenol monooxygenase and lincomysin biosynthesis in Streptomyces lincolnensis. 81 70

The ageing phenomenon exhibited by the ascomycetous fungus Podospora anserina can be either delayed or induced by either different carbon sources or effectors. As these effects seem to have analogy to catabolite-repression of respiratory genes, experiments concerning respiratory functions have been carried out. Ageing is parallelled by switching from cytochrome c-oxidase-mediated respiration to alternative, cyanide-resistant respiration for reasons still unknown. The latter is always accompanied by appearance of the phenol oxidizing enzyme laccase (EC 1.10.3.2), which seems to act as an alternative oxidase. The existence of a second, non-mitochondrially encoded respiratory pathway relieves the selective pressure on mitochondria leading to disintegrated, non-functional mtDNA and thereby whole mitochondria which accumulate in the hyphal cells. Mutants lacking cytochrome c-oxidase aa3 or laccase have stable mitochondrial populations and live eternally.
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PMID:Oxidative stress and ageing in the fungus Podospora anserina. 133 31

The production in a 5-1 fermenter of the extracellular enzymes laccase and aryl-alcohol oxidase by the fungus Pleurotus eryngii was studied. The latter enzyme has been purified 50-fold by Sephacryl S-200 and Mono Q chromatography. Purified aryl-alcohol oxidase is a unique flavoprotein with 15% carbohydrate content, a molecular mass of 72.6 kDa (SDS/PAGE) and a pI of 3.9. The enzyme presents wide specificity, showing activity on benzyl, cinnamyl, naphthyl and aliphatic unsaturated alcohols. Neither activity nor inhibition of veratryl alcohol oxidation was found with saturated alcohols, but competitive inhibition was produced by aromatic compounds which were not aryl-alcohol oxidase substrates, such as phenol or 3-phenyl-1-propanol. From these results, it was apparent that a double bond conjugated with a primary alcohol is necessary for substrate recognition by aryl-alcohol oxidase, and that activity is increased by the presence of additional conjugated double bonds and electron donor groups. Both affinity and maximal velocity during enzymic oxidation of methoxybenzyl alcohols were affected in a similar way by ring substituents, increasing from benzyl alcohol (Km = 0.84 mM, Vmax = 52 U/mg) to 4-methoxybenzyl alcohol (Km = 0.04 mM, Vmax = 208 U/mg). Aryl-alcohol oxidase presents also a low oxidase activity with aromatic aldehydes, but the highest activity was found in the presence of electron-withdrawing groups.
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PMID:Substrate specificity and properties of the aryl-alcohol oxidase from the ligninolytic fungus Pleurotus eryngii. 142 67

Phenol oxidase of Fasciola gigantica exists both as the soluble form as well as the membrane-bound form. The membrane-bound enzyme is considered to be a tyrosinase type because it is capable of oxidizing mono- and diphenol and is inefficient in oxidizing paraphenols. The soluble enzyme is a laccase type showing more affinity to various diphenols and paraphenols. Membrane-bound enzyme exists as isoenzymes, showing 3 fractions, of which the slow-moving fraction is capable of oxidizing both 4-methyl catechol and catechol, whereas the two remaining fractions are specific to 4-methyl catechol only. Soluble enzyme exists as a single homogeneous form showing affinity to both mono- and diphenols. Inhibition of the enzyme by potassium iodide and mercuric chloride indicates the active tyrosyl and SH groups of the enzyme. Inhibition of the enzyme by sodium diethyl dithiocarbamate and phenyl thiourea indicates that copper is the prosthetic group of the enzyme.
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PMID:Properties of phenol oxidase in Fasciola gigantica. 251 8

The ability of a polyphenoloxidase, the laccase of the fungus Rhizoctonia praticola, to detoxify phenolic pollutants was examined. The growth of the fungus could be inhibited by phenolic compounds, and the effective concentration was dependent on the substituents of the phenol. A toxic amount of a phenolic compound was added to a fungal growth medium in the presence or absence of a naturally occurring phenol, and half of the replicates also received laccase. The medium was then inoculated with R. praticola, and the levels of phenols in the medium were monitored by high-performance liquid chromatography analysis. The addition of the laccase reversed the inhibitory effect of 2,6-xylenol, 4-chloro-2-methylphenol, and p-cresol. Other compounds, e.g., o-cresol and 2,4-dichlorophenol, were detoxified only when laccase was used in conjunction with a natural phenol such as syringic acid. The toxicity of p-chlorophenol and 2,4,5-trichlorophenol could not be overcome by any additions. The ability of the laccase to alter the toxicity of the phenols appeared to be related to the capacity of the enzyme to decrease the levels of the parent compound by transformation or cross-coupling with another phenol.
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PMID:Laccase-mediated detoxification of phenolic compounds. 322 71

Rapidly growing Neurospora crassa does not produce laccase (p-diphenol:oxygen oxidoreductase; EC 1.10.3.2). Low concentrations of cycloheximide induce the production of this enzyme, most of which is secreted into the media. In general, limited inhibition of protein synthesis seems to derepress laccase synthesis since actinomycin D and, to a limited extent, puromycin also induce laccase production. Similarities in the conditions of laccase and tyrosinase induction, plus investigations with two tyrosinase regulatory mutants, suggest that the production of these two phenol oxidases is controlled by the same mechanism. As shown by polyacrylamide gel electrophoresis, most of the 10 to 12 proteins normally present in the medium virtually disappear during cycloheximide treatment. In contrast, the amounts of two proteins that are present in only very minor quantities, if at all, in normal culture filtrates increase dramatically. One of these proteins co-migrates with laccase, whereas the other has not been identified.
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PMID:Induction of Neurospora crassa laccase with protein synthesis inhibitors. 427 35

3,4-Dihydroxyphenylalanine (DOPA) is not a preferred substrate of Rhus vernicifera laccase, as rate constants for the anaerobic reduction of the type 1 cupric atom by L-DOPA (6.3 X 10(1) M-1 s-1), D-DOPA (2.6 X 10(1) M-1 s-1), and L-DOPA methyl ester (2.6 X 10(1) M-1 s-1) are considerably smaller than k1 (catechol) (7 X 10(2) M-1 s-1) and rate constants characteristic of numerous other nonphysiological organic substrates (25 degrees C, pH 7.0, I = 0.5 M). The reactions of DOPA derivatives with laccase are unique, however, in that a two-term rate law pertains: kobsd = k0 + k1[phenol]; k0(L-DOPA) = 7 X 10(-2) s-1. The reactivities of other catechol derivatives (pyrogallol, gallic acid, and methyl gallate) with laccase type 1 copper were also examined.
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PMID:Reduction of laccase type 1 copper by 3,4-dihydroxyphenylalanine and other catechol derivatives. 622 99

Aspergillus terreus dihydrogeodin oxidase (DHGO) is an enzyme catalyzing the stereospecific phenol oxidative coupling reaction converting dihydrogeodin to (+)- geodin. We previously reported the purification of DHGO from A. terreus and raised polyclonal antibody against DHGO. From the first cDNA library constructed in lambda gt11 using mRNA from 3-day-old mycelium of A. terreus, four clones were identified using anti-DHGO antibody, but all contained partial cDNA inserts around 280 base pairs. This cDNA fragment was used as a probe to clone the genomic DNA and cDNA for dihydrogeodin oxidase from A. terreus. The sequence of the cloned DHGO genomic DNA and cDNA predicted that the DHGO polypeptide consists of 605 amino acids showing significant homology with multicopper blue proteins such as laccase and ascorbate oxidase. Four potential copper binding domains exist in DHGO polypeptide. The DHGO gene consists of seven exons separated by six short introns. Expression of the DHGO gene in Aspergillus nidulans under the starch or maltose-inducible Taka-amylase A promoter as an active enzyme established the functional identity of the gene. Also, introduction of the genomic DNA for DHGO into Penicillium frequentans led to the production of DHGO polypeptide as judged by Western blot analysis.
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PMID:Molecular cloning and heterologous expression of the gene encoding dihydrogeodin oxidase, a multicopper blue enzyme from Aspergillus terreus. 766 60

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

The cytochemical localization of the phenol oxidases, laccase and peroxidase, has been studied in pro-lignifying and lignifying Coleus blumei stem sections using 4-methoxy-alpha-naphthol as substrate. The results illustrated that, for short incubation times, both pro-lignifying and lignifying Coleus sections showed H2O2-dependent phenol oxidase (peroxidase-like) activity in epidermal and vascular tissues, while no detectable H2O2-independent phenol oxidase (laccase-like) activity was found in Coleus tissues. For long incubation times, H2O2-independent phenol-oxidases can also be detected in these tissues, however, this is probably due to the partial capability of intercellular washing fluid Coleus peroxidase to oxidize 4-methoxy-alpha-naphthol in the absence of exogenously added H2O2. This illustrates not only the importance of the substrate used, but also the importance of the incubation time, in the cytochemical localization of phenol oxidizing enzymes.
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PMID:Cytochemical localization of phenol-oxidizing enzymes in lignifying Coleus blumei stems. 917 41


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