Abstract
Laccases are blue copper oxidases (E.C. 1.10.3.2 benzenediol: oxygen oxidoreductase) that catalyze the one-electron oxidation of phenolics, aromatic amines, and other electron-rich substrates with the concomitant reduction of O2 to H2O. They are currently seen as highly interesting industrial enzymes because of their broad substrate specificity. A positive strain was isolated and characterized as nonspore forming Basidiomycetes Pleurotus sp. Laccase activity was determined using ABTS as substrate. Laccase was purified by ionexchange and gel filtration chromatography. The purified laccase was a monomer showed a molecular mass of 40 ± 1 kDa as estimated by SDS-PAGE and a 72-fold purification with a 22% yield. The optimal pH and temperature were 4.5 and 65°C, respectively. The K m and V max values are 250 (mM) and 0.33 (μmol/min), respectively, for ABTS as substrate. Metal ions like CuSO4, BaCl2, MgCl2, FeCl2, ZnCl2 have no effect on purified laccase whereas HgCl2 and MnCl2 moderately decrease enzyme activity. SDS and sodium azide inhibited enzyme activity, whereas Urea, PCMB, DTT, and mercaptoethanol have no effect on enzyme activity. The isolated laccase can be used in development of biosensor for detecting the phenolic compounds from the effluents of paper industries.
Highlights
Laccases (EC 1.10.3.2; benzenediol: oxygen oxidoreductases) are multicopper enzymes belonging to the group of blue oxidases that catalyses oxidation of a wide variety of organic and inorganic compounds, including diphenols, polyphenols, diamines, and aromatic amines
Chemicals: all chemicals were of the GR grade, (ABTS), syringaldazine were from Sigma
The SDS-PAGE results showed that Pleurotus spp. laccase has a molecular weight of 40 ± 1 kDa, close to that of laccases from P. chrysosporium having molecular weight of 46.5 kD which is in the range reported for other basidiomycetes [38]
Summary
Laccases (EC 1.10.3.2; benzenediol: oxygen oxidoreductases) are multicopper enzymes belonging to the group of blue oxidases that catalyses oxidation of a wide variety of organic and inorganic compounds, including diphenols, polyphenols, diamines, and aromatic amines. The substrates of laccases may vary from diphenols and polyphenols to diamines, aromatic amines, benzenethiols, and substituted phenols [3]. Most of the laccases studied are of fungal origin especially from the classes of white-rot fungi. Fungal laccases play an important role in plant pathogenesis, pigment production, and degradation of lignocellulosic materials [1, 2]. The ability of laccase producing microorganisms or purified laccases to eliminate a wide range of pollutants is currently one of the most interesting subjects for researchers in environmental biotechnology [5]. Ethanol is produced from pulp, manufacturing of lightening cream, wine clarification, and is used in industrial applications such as an oxidizing
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