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)

The reactions of nitric oxide (NO) with the oxidized and reduced forms of fungal and tree laccase, as well as with tree laccase depleted in type 2 copper, are reported. The products of the reactions were determined by NMR and mass spectroscopy, whereas the oxidation states of the enzymes were monitored by EPR and optical spectroscopy. All three copper sites in fungal laccase are reduced by NO. In addition, NO forms a specific complex with the reduced type 2 copper. NO similarly reduces all of the copper sites in tree laccase, but it also oxidizes the reduced sites produced by ascorbate or NO reduction. A catalytic cycle is set up in which N2O, NO2-, and various forms of the enzyme are produced. On freezing of fully reduced tree laccase in the presence of NO, the type 1 copper becomes reoxidized. This reaction does not occur with the enzyme depleted in type 2 copper, suggesting that it involves intramolecular electron transfer from the type 1 copper to NO bound to the type 2 copper. When the half-oxidized tree laccase is formed in the presence of NO, a population of molecules exists which exhibits a type 3 EPR signal. A triplet EPR signal is also seen in the same preparation and is attributed to a population of the enzyme molecules in which NO is bound to the reduced copper of a half-oxidized type 3 copper site.
Biochemistry 1981 Sep 01
PMID:Reactions of nitric oxide with tree and fungal laccase. 627 Nov 78

We report results of experiments designed to characterize the Type 1 and Type 3 copper sites in Rhus laccase depleted of Type 2 copper (T2D). Use of the Lowry method for determining protein concentration yielded the value 5620 +/- 570 M-1 cm-1 for the extinction of the 615-nm absorption band of this protein. Anaerobic reductive titrations with Ru(NH)3)6(2)+ and Cr(II)aq ions established the presence of three electron-accepting centers, which are reduced in a complex manner. Treatment of T2D laccase with a 70-fold excess of H2O2 induced a new shoulder at 330 nm (delta epsilon = 660 M-1 cm-1), as well as intensity perturbations at 280 and 615 nm. Comparison of difference spectra show that this 330-nm band derives from a Type 3 copper-bound peroxide and not from a reoxidized Type 3 site. Dioxygen reoxidation of ascorbate-reduced T2D laccase produced new difference bands at 330 nm (delta epsilon = 770 M-1 cm-1) and 270 nm (delta epsilon = 13,000 M-1 cm-1), the former assigned to a bound peroxide which is a dioxygen reduction intermediate. In the corresponding epr spectrum of this material new Cu(II) g parallel features (A parallel approximately 130 G) indicative of an isolated copper ion and a triplet signal near 3,400 G were observed, originating from the Type 3 sites of separate T2D laccase molecules. Reoxidation by ferricyanide or by dioxygen as mediated by iron hexacyanide did not produce these changes. Thus the magnetism of the reoxidized Type 3 site in T2D laccase can be perturbed as a consequence of aerobic turnover. The suggestion is advanced that there are presently three forms of T2D laccase, possibly metastable conformational isotypes, accounting for the apparently contradictory reports on the properties of this protein.
J Biol Chem 1983 Sep 25
PMID:The Type 3 copper site is intact but labile in Type 2-depleted laccase. 630 31

Spectrophotometric determination of laccase activity may be affected by the formation of quinoid chromophores arising from nonenzymatic oxidations interfering with enzymatic reactions. Km values for guaiacol obtained by spectrophotometric and HPLC methods confirm the above hypothesis. HPLC results are particularly useful for the assay of laccase activity on natural phenolic extracts.
Anal Biochem 1983 Sep
PMID:Laccase assay by means of high-performance liquid chromatography. 663 92

Conidial laccase of Aspergillus nidulans was purified by standard protein purification methods. Although the purified material showed a cluster of several protein bands on a nondenaturing gel, each of these protein bands had laccase activity. All bands of activity, however, were absent in a strain carrying a mutation in the structural gene for laccase. Concentrated solutions (greater than 1 mg/ml) were bright blue, suggesting that, like other laccases, this enzyme contains copper. The enzyme contained asparagine-linked carbohydrate (12% by weight) which could be removed by digestion with endo-beta-N-acetylglucosaminidase H. The molecular weight of native enzyme as determined by gel filtration was 110,000, but the largest component in a sodium dodecyl sulfate gel was 80,000. Several smaller components (55,000 and 36,000 molecular weight) were also visible. We present evidence which suggests that the smaller components are in vivo cleavage products tightly associated with enzymatically active molecules. Comparison of the laccase from a white-spore (wA) and a green-spore (wA+) strain showed, surprisingly, that the enzymes differed in electrophoretic pattern, in vitro heat stability, and in vivo metabolic stability. The difference was manifested for enzymes isolated from cultures after conidial pigmentation of the wA+ strain had occurred. If examined earlier, before pigmentation, the enzymes were indistinguishable. Since wA strains lack the precursor of the wild-type green pigment, i.e., the laccase substrate, we suggest that the transformation of the enzyme of the wA strain is due to its failure to interact with its normal substrate.
J Bacteriol 1982 Sep
PMID:Purification and characterization of the conidial laccase of Aspergillus nidulans. 705 88

A kinetic study of inhibition of Polyporus versicolor laccase activity by fluoride-, chloride- and bromide ions has been carried out. It has been found that the fluoride ion is a non-competitive inhibitor with respect to the electron donor and a mixed inhibitor with respect to oxygen. However, the chloride and bromide ions are competitive inhibitors with respect to the electron donor. The constants of inhibition of the enzyme activity by both chloride and fluoride ions and the catalytic constant were found to be pH-dependent. Based on the pH-dependence of the catalytic constant, an existence of two ionogenic groups in the enzyme active site has been proposed. The existence of an alternative electron pathway in the enzyme active site is postulated. This pathway makes a noticeable contribution to the reaction rate when the concentration of the electron donor and the fluoride ion is high. This alternative electron pathway can be blocked by the chloride ions and the hydroxyl ions taken at high concentrations. A formal kinetic description of this phenomenon has been given and the role of the type 2 Cu2+ in the catalytic process has been evaluated.
Biokhimiia 1981 Sep
PMID:[Inhibition mechanism of Polyporus versicolor laccase by halide ions]. 729 28

A biosensor was used for the analysis of catecholamines in media and lysates of cultured bovine adrenal chromaffin cells. The sensor is composed of coimmobilised laccase and glucose dehydrogenase coupled with an oxygen electrode, using the catalytic effect of cate cholamines for glucose oxidation in this system. The analysis time is almost 5 min. The correlation between the biosensor and HPLC determination is 0.99.
Pharmazie 1995 Sep
PMID:A new sensitive and simple method for detection of catecholamines from adrenal chromaffin cells. 748 95

Addition of miscible organic solvents to water increases the solubility of naphthalene. The logarithm of the solubility is linearly dependent on the co-solvent concentration, in an intermediate range. The relative solubilising effects of different solvents correlate well with their known tendency to denature proteins (using literature data for trypsin, cytochrome c, chymotrypsinogen, chymotrypsin, laccase and myoglobin). This is expected if denaturation occurs when the hydrophobic effect has been reduced by a characteristic extent for a given protein. Naphthalene solubility predicts denaturation as well as does the denaturation capacity model.
Biochim Biophys Acta 1995 Sep 27
PMID:Prediction of denaturing tendency of organic solvents in mixtures with water by measurement of naphthalene solubility. 754 59

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.
J Biol Chem 1995 Sep 15
PMID:Molecular cloning and heterologous expression of the gene encoding dihydrogeodin oxidase, a multicopper blue enzyme from Aspergillus terreus. 766 60

A gene coding for the multi-copper phenol oxidase laccase has been isolated from the white-rot basidiomycete Trametes versicolor. The gene, which is preceded by a TATA box and a pyrimidine-rich region, is predicted to contain ten introns. The mature translation product, preceded by a 22-residue signal peptide, should consist of 498 residues. Comparisons with Edman degradation data of peptides from T. versicolor laccase strongly suggest that two disulfide bridges are formed by Cys-85/Cys-487 and Cys-117/Cys-205, respectively. The encoded protein contains five Cys, and the sequence surrounding the remaining Cys-452 is consistent with its involvement in the ligation of type-1 copper. Alignment of sequences indicates that T. versicolor laccase displays a Phe at the position corresponding to a residue (Met in ascorbate oxidase and azurin) considered important for the reduction potential of type-1 copper proteins.
Biochim Biophys Acta 1995 Sep 06
PMID:Characterization of a laccase gene from the white-rot fungus Trametes versicolor and structural features of basidiomycete laccases. 766 13

Myrothecium verrucaria bilirubin oxidase (EC 1.3.3.5) is an enzyme catalyzing the oxidation of bilirubin to biliverdin and other substrates. We have purified bilirubin oxidase from the medium of M. verrucaria and determined its partial amino acid sequence and isolated cDNA fragment amplified by polymerase chain reaction using oligonucleotide primers designed on the basis of the partial amino acid sequence. The gene for bilirubin oxidase has been cloned from a genomic library using the cDNA fragment as a probe. The gene encodes a precursor of bilirubin oxidase consisting of 572 amino acid residues, which comprises the prepro-region of 38 amino acid residues and the mature enzyme of 534 amino acid residues containing one cysteine. Five introns were found within the coding region. Sequence comparison of bilirubin oxidase with other blue copper proteins (laccase, ascorbate oxidase, human ceruloplasmin, plastocyanin, and azurin) revealed the presence of four domains corresponding to potential copper ligands. We have expressed this bilirubin oxidase gene in Saccharomyces cerevisiae under the repressible acid phosphatase promotor and found an active recombinant bilirubin oxidase, establishing the functional identity of the gene.
J Biol Chem 1993 Sep 05
PMID:Molecular cloning of the gene for bilirubin oxidase from Myrothecium verrucaria and its expression in yeast. 836 Jan 71


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