Phylogenetic and biochemical characterisation of a recombinant laccase fromTrametes versicolor

Mechanistic Insights into the Biodegradation of Carbon Dots by Fungal Laccase

While carbon dots (CDs) have the potential to support the agricultural revolution, it remains obscure about their environmental fate and bioavailability by plants. Fungal laccase-mediated biotransformation of carbon nanomaterials has received little attention despite its known capacity to eliminate recalcitrant contaminants. Herein, we presented the initial investigation into the transformation of CDs by fungal laccase. The degradation rates of CDs were determined to be first-order in both substrate and enzyme. Computational docking studies showed that CDs preferentially bonded to the pocket of laccase on the basal plane rather than the edge through hydrogen bonds and hydrophobic interactions. Electrospray ionization-Fourier transform-ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) and other characterizations revealed that the phenolic/amino lignins and tannins portions in CDs are susceptible to laccase transformation, resulting in graphitic structure damage and smaller-sized fragments. By using the 13C stable isotope labeling technique, we quantified the uptake and translocation of 13C-CDs by mung bean plants. 13C-CDs (10 mg L-1) accumulated in the root, stem, and leaf were estimated to be 291, 239, and 152 μg g-1 at day 5. We also evidenced that laccase treatment alters the particle size and surface chemistry of CDs, which could facilitate the uptake of CDs by plants and reduce their nanotoxicity to plants.

Laccase: Various types and applications

Laccase belongs to the polyphenol oxidase family and is very important in removing environmental pollutants due to its structural and functional properties. Recently, the ability of laccase to oxidize phenolic and nonphenolic substances has been considered by many researchers. This enzyme's application scope includes a broad range of chemical processes and industrial usages, such as bioremediation, nanobiotechnology, woodworking industries, bleaching of paper pulp, dyeing in the textile industry, biotechnological uses in food industries, biorefining, detoxification from wastewater, production of organic matter from phenolic and amine substrates, and biofuels. Although filamentous fungi produce large amounts of laccase, high-yield industrial-scale production of laccase is still faced with many problems. At present, researchers are trying to increase the efficiency and productivity and reduce the final price of laccase by finding suitable microorganisms and improving the process of production and purification of laccase. This article reviews the introduction of laccase, its properties, production processes, and the effect of various factors on the enzyme's stability and activity, and some of its applications in various industries.

Involvement of laccase-like enzymes in humic substance degradation by diverse polar soil bacteria

Humic substances (HS) in soil are widely distributed in cold environments and account for a significant fraction of soil's organic carbon. Bacterial strains (n = 281) were isolated at 15 °C using medium containing humic acids (HA), a principal component of HS, from a variety of polar soil samples: 217 from the Antarctic and 64 from the Arctic. We identified 73 potential HA-degrading bacteria based on 16S rRNA sequence similarity, and these sequences were affiliated with phyla Proteobacteria (73.9%), Actinobacteria (20.5%), and Bacteroidetes (5.5%). HA-degrading strains were further classified into the genera Pseudomonas (51 strains), Rhodococcus (10 strains), or others (12 strains). Most strains degraded HA between 10 and 25 °C, but not above 30 °C, indicating cold-adapted degradation. Thirty unique laccase-like multicopper oxidase (LMCO) gene fragments were PCR-amplified from 71% of the 73 HA-degrading bacterial strains, all of which included conserved copper-binding regions (CBR) I and II, both essential for laccase activity. Bacterial LMCO sequences differed from known fungal laccases; for example, a cysteine residue between CBR I and CBR II in fungal laccases was not detected in bacterial LMCOs. This suggests a bacterial biomarker role for LMCO to predict changes in HS-degradation rates in tundra regions as global climate changes. Computer-aided molecular modeling showed these LMCOs contain a highly-conserved copper-dependent active site formed by three histidine residues between CBR I and CBR II. Phylogenetic- and modeling-based methods confirmed the wide occurrence of LMCO genes in HA-degrading polar soil bacteria and linked their putative gene functions with initial HS-degradation processes.

Kin Recognition in the Parasitic Plant Triphysaria versicolor Is Mediated Through Root Exudates

Triphysaria is a facultative parasitic plant in the Orobanchaceae that parasitizes the roots of a wide range of host plants including Arabidopsis, Medicago, rice and maize. The important exception to this broad host range is that Triphysaria rarely parasitize other Triphysaria. We explored self and kin recognition in Triphysaria versicolor and showed that exudates collected from roots of host species, Arabidopsis thaliana and Medicago truncatula, induced haustorium development when applied to the roots of Triphysaria seedlings in vitro while those collected from Triphysaria did not. In mixed exudate experiments, Triphysaria exudates did not inhibit the haustorium-inducing activity of those from host roots. Interestingly, when roots of Triphysaria seedlings were treated with either horseradish peroxidase or fungal laccase, the extracts showed haustorium-inducing factor (HIF) activity, suggesting that Triphysaria roots contain the proper substrates for producing HIFs. Transgenic Triphysaria roots overexpressing a fungal laccase gene TvLCC1 showed an increased responsiveness to a known HIF, 2,6-dimethoxy benzoquinone (DMBQ), in developing haustoria. Our results indicate kin recognition in Triphysaria is associated with the lack of active HIFs in root exudates. Treatment of Triphysaria roots with enzymatic oxidases activates or releases molecules that are HIFs. This study shows that exogenously applied oxidases can activate HIFs in Triphysaria roots that had no previous HIF activity. Further studies are necessary to determine if differential oxidase activities in host and parasite roots account for the kin recognition in haustorium development.

Evolutionary Relationships Between the Laccase Genes of Polyporales: Orthology-Based Classification of Laccase Isozymes and Functional Insight From Trametes hirsuta

Laccase is one of the oldest known and intensively studied fungal enzymes capable of oxidizing recalcitrant lignin-resembling phenolic compounds. It is currently well established that fungal genomes almost always contain several non-allelic copies of laccase genes (laccase multigene families); nevertheless, many aspects of laccase multigenicity, for example, their precise biological functions or evolutionary relationships, are mostly unknown. Here, we present a detailed evolutionary analysis of the sensu stricto laccase genes (CAZy - AA1_1) from fungi of the Polyporales order. The conducted analysis provides a better understanding of the Polyporales laccase multigenicity and allows for the systemization of the individual features of different laccase isozymes. In addition, we provide a comparison of the biochemical and catalytic properties of the four laccase isozymes from Trametes hirsuta and suggest their functional diversification within the multigene family.

Yeast Hosts for the Production of Recombinant Laccases: A Review

Laccases are multi-copper oxidoreductases which catalyze the oxidation of a wide range of substrates during the simultaneous reduction of oxygen to water. These enzymes, originally found in fungi, plants, and other natural sources, have many industrial and biotechnological applications. They are used in the food, textile, pulp, and paper industries, as well as for bioremediation purposes. Although natural hosts can provide relatively high levels of active laccases after production optimization, heterologous expression can bring, moreover, engineered enzymes with desired properties, such as different substrate specificity or improved stability. Hence, diverse hosts suitable for laccase production are reviewed here, while the greatest emphasis is placed on yeasts which are commonly used for industrial production of various proteins. Different approaches to optimize the laccase expression and activity are also discussed in detail here.

Cloning and Expression Analysis of Vvlcc3, a Novel and Functional Laccase Gene Possibly Involved in Stipe Elongation

Volvariella volvacea, usually harvested in its egg stage, is one of the most popular mushrooms in Asia. The rapid transition from the egg stage to elongation stage, during which the stipe stretches to almost full length leads to the opening of the cap and rupture of the universal veil, and is considered to be one of the main factors that negatively impacts the yield and value of V. volvacea. Stipe elongation is a common phenomenon in mushrooms; however, the mechanisms, genes and regulation involved in stipe elongation are still poorly understood. In order to study the genes related to the stipe elongation, we analyzed the transcription of laccase genes in stipe tissue of V. volvacea, as some laccases have been suggested to be involved in stipe elongation in Flammulina velutipes. Based on transcription patterns, the expression of Vvlcc3 was found to be the highest among the 11 laccase genes. Moreover, phylogenetic analysis showed that VvLCC3 has a high degree of identity with other basidiomycete laccases. Therefore, we selected and cloned a laccase gene, named Vvlcc3, a cDNA from V. volvacea, and expressed the cDNA in Pichia pastoris. The presence of the laccase signature L1-L4 on the deduced protein sequence indicates that the gene encodes a laccase. Phylogenetic analysis showed that VvLCC3 clusters with Coprinopsis cinerea laccases. The ability to catalyze ABTS (2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) oxidation proved that the product of the Vvlcc3 gene was a functional laccase. We also found that the expression of the Vvlcc3 gene in V. volvacea increased during button stage to the elongation stage; it reached its peak in the elongation stage, and then decreased in the maturation stage, which was similar to the trend in the expression of Fv-lac3 and Fv-lac5 in F. velutipes stipe tissue. The similar trend in expression level of these laccase genes of F. velutipes suggested that this gene could be involved in stipe elongation in V. volvacea.

The Trametes hirsuta 072 laccase multigene family: Genes identification and transcriptional analysis under copper ions induction

Laccases, blue copper-containing oxidases, ≿ an play an important role in a variety of natural processes. The majority of fungal laccases are encoded by multigene families that express closely related proteins with distinct functions. Currently, only the properties of major gene products of the fungal laccase families have been described. Our study is focused on identification and characterization of laccase genes, which are transcribed in basidiomycete Trametes hirsuta 072, an efficient lignin degrader, in a liquid medium, both without and with induction of laccase transcription by copper ions. We carried out production of cDNA libraries from total fungal RNA, followed by suppression subtractive hybridization and mirror orientation selection procedures, and then used Next Generation Sequencing to identify low abundance and differentially expressed laccase transcripts. This approach resulted in description of five laccase genes of the fungal family, which, according to the phylogenetic analysis, belong to distinct clusters within the Trametes genus. Further analysis established similarity of physical, chemical, and catalytic properties between laccases inside each cluster. Structural modeling suggested importance of the sequence differences in the clusters for laccase substrate specificity and catalytic efficiency. The implications of the laccase variations for the fungal physiology are discussed.

The comparative study of a laccase-natural clinoptilolite-based catalyst activity and free laccase activity on model compounds

For the first time a laccase from Trametes versicolor was immobilized on a natural clinoptilolite with Si/Al=5 to obtain a biocatalyst for environmental applications. Immobilization procedures exploiting adsorption and covalent binding were both tested, and only the last provided enough activity for practical applications. The optimal conditions for the immobilization of the enzyme on the support and the kinetic parameters for the free and covalent bonded laccase were determined. The laccase bonded to the zeolitic support showed a lower activity than the free laccase, but the pH and thermal stability were greater. 20 mg of dry biocatalyst containing 1 U of laccase were able to remove in 50h 73-78% of 2-chlorophenol and 2,4-dichlorophenol in relatively concentrated aqueous solutions (100 μmol L(-1)).

Multicopper oxidase-1 orthologs from diverse insect species have ascorbate oxidase activity

Members of the multicopper oxidase (MCO) family of enzymes can be classified by their substrate specificity; for example, ferroxidases oxidize ferrous iron, ascorbate oxidases oxidize ascorbate, and laccases oxidize aromatic substrates such as diphenols. Our previous work on an insect multicopper oxidase, MCO1, suggested that it may function as a ferroxidase. This hypothesis was based on three lines of evidence: RNAi-mediated knock down of Drosophila melanogaster MCO1 (DmMCO1) affects iron homeostasis, DmMCO1 has ferroxidase activity, and DmMCO1 has predicted iron binding residues. In our current study, we expanded our focus to include MCO1 from Anopheles gambiae, Tribolium castaneum, and Manduca sexta. We verified that MCO1 orthologs have similar expression profiles, and that the MCO1 protein is located on the basal surface of cells where it is positioned to oxidize substrates in the hemolymph. In addition, we determined that RNAi-mediated knock down of MCO1 in A. gambiae affects iron homeostasis. To further characterize the enzymatic activity of MCO1 orthologs, we purified recombinant MCO1 from all four insect species and performed kinetic analyses using ferrous iron, ascorbate and two diphenols as substrates. We found that all of the MCO1 orthologs are much better at oxidizing ascorbate than they are at oxidizing ferrous iron or diphenols. This result is surprising because ascorbate oxidases are thought to be specific to plants and fungi. An analysis of three predicted iron binding residues in DmMCO1 revealed that they are not required for ferroxidase or laccase activity, but two of the residues (His374 and Asp380) influence oxidation of ascorbate. These two residues are conserved in MCO1 orthologs from insects and crustaceans; therefore, they are likely to be important for MCO1 function. The results of this study suggest that MCO1 orthologs function as ascorbate oxidases and influence iron homeostasis through an unknown mechanism.

Stability Mechanisms of Laccase Isoforms using a Modified FoldX Protocol Applicable to Widely Different Proteins

A recent computational protocol that accurately predicts and rationalizes protein multisite mutant stabilities has been extended to handle widely different isoforms of laccases. We apply the protocol to four isoenzymes of Trametes versicolor laccase (TvL) with variable lengths (498-503 residues) and thermostability (Topt ∼ 45-80 °C) and with 67-77% sequence identity. The extended protocol uses (i) statistical averaging, (ii) a molecular-dynamics-validated "compromise" homology model to minimize bias that causes proteins close in sequence to a structural template to be too stable due to having the benefits of the better sampled template (typically from a crystal structure), (iii) correction for hysteresis that favors the input template to overdestabilize, and (iv) a preparative protocol to provide robust input sequences of equal length. The computed ΔΔG values are in good agreement with the major trends in experimental stabilities; that is, the approach may be applicable for fast estimates of the relative stabilities of proteins with as little as 70% identity, something that is currently extremely challenging. The computed stability changes associated with variations are Gaussian-distributed, in good agreement with experimental distributions of stability effects from mutation. The residues causing the differential stability of the four isoforms are consistent with a range of compiled laccase wild type data, suggesting that we may have identified general drivers of laccase stability. Several sites near Cu, notably 79, 241, and 245, or near substrate, mainly 265, are identified that contribute to stability-function trade-offs, of relevance to the search for new proficient and stable variants of these important industrial enzymes.

Stability mechanisms of a thermophilic laccase probed by molecular dynamics

Laccases are highly stable, industrially important enzymes capable of oxidizing a large range of substrates. Causes for their stability are, as for other proteins, poorly understood. In this work, multiple-seed molecular dynamics (MD) was applied to a Trametes versicolor laccase in response to variable ionic strengths, temperatures, and glycosylation status. Near-physiological conditions provided excellent agreement with the crystal structure (average RMSD ∼0.92 Å) and residual agreement with experimental B-factors. The persistence of backbone hydrogen bonds was identified as a key descriptor of structural response to environment, whereas solvent-accessibility, radius of gyration, and fluctuations were only locally relevant. Backbone hydrogen bonds decreased systematically with temperature in all simulations (∼9 per 50 K), probing structural changes associated with enthalpy-entropy compensation. Approaching T_opt (∼350 K) from 300 K, this change correlated with a beginning “unzipping” of critical β-sheets. 0 M ionic strength triggered partial denucleation of the C-terminal (known experimentally to be sensitive) at 400 K, suggesting a general salt stabilization effect. In contrast, F⁻ (but not Cl⁻) specifically impaired secondary structure by formation of strong hydrogen bonds with backbone NH, providing a mechanism for experimentally observed small anion destabilization, potentially remedied by site-directed mutagenesis at critical intrusion sites. N-glycosylation was found to support structural integrity by increasing persistent backbone hydrogen bonds by ∼4 across simulations, mainly via prevention of F⁻ intrusion. Hydrogen-bond loss in distinct loop regions and ends of critical β-sheets suggest potential strategies for laboratory optimization of these industrially important enzymes.

Heterologous laccase production and its role in industrial applications

Laccases are blue multicopper oxidases, catalyzing the oxidation of an array of aromatic substrates concomitantly with the reduction of molecular oxygen to water. These enzymes are implicated in a variety of biological activities. Most of the laccases studied thus far are of fungal origin. The large range of substrates oxidized by laccases has raised interest in using them within different industrial fields, such as pulp delignification, textile dye bleaching, and bioremediation. Laccases secreted from native sources are usually not suitable for large-scale purposes, mainly due to low production yields and high cost of preparation/purification procedures. Heterologous expression may provide higher enzyme yields and may permit to produce laccases with desired properties (such as different substrate specificities, or improved stabilities) for industrial applications. This review surveys researches on heterologous laccase expression focusing on the pivotal role played by recombinant systems towards the development of robust tools for greening modern industry.

Secretion profiles of fungi as potential tools for metal ecotoxicity assessment: a study of enzymatic system in Trametes versicolor

The relationship between the expression of extracellular enzymatic system and a metal stress is scarce in fungi, hence limiting the possible use of secretion profiles as tools for metal ecotoxicity assessment. In the present study, we investigated the effect of Zn, Cu, Pb and Cd, tested alone or in equimolar cocktail, on the secretion profiles at enzymatic and protein levels in Trametesversicolor. For that purpose, extracellular hydrolases (acid phosphatase, β-glucosidase, β-galactosidase and N-acetyl-β-glucosaminidase) and ligninolytic oxidases (laccase, Mn-peroxidase) were monitored in liquid cultures. Fungal secretome was analyzed by electrophoresis and laccase secretion was characterized by western-blot and mass spectrometry analyses. Our results showed that all hydrolase activities were inhibited by the metals tested alone or in cocktail, whereas oxidase activities were specifically stimulated by Cu, Cd and metal cocktail. At protein level, metal exposure modified the electrophoretic profiles of fungal secretome and affected the diversity of secreted proteins. Two laccase isoenzymes, LacA and LacB, identified by mass spectrometry were differentially glycosylated according to the metal exposure. The amount of secreted LacA and LacB was strongly correlated with the stimulation of laccase activity by Cu, Cd and metal cocktail. These modifications of extracellular enzymatic system suggest that fungal oxidases could be used as biomarkers of metal exposure.

Lignin-modifying enzymes in filamentous basidiomycetes--ecological, functional and phylogenetic review

Filamentous fungi owe powerful abilities for decomposition of the extensive plant material, lignocellulose, and thereby are indispensable for the Earth's carbon cycle, generation of soil humic matter and formation of soil fine structure. The filamentous wood-decaying fungi belong to the phyla Basidiomycota and Ascomycota, and are unique organisms specified to degradation of the xylem cell wall components (cellulose, hemicelluloses, lignins and extractives). The basidiomycetous wood-decaying fungi form brackets, caps or resupinaceous (corticioid) fruiting bodies when growing on wood for dissemination of their sexual basidiospores. In particular, the ability to decompose the aromatic lignin polymers in wood is mostly restricted to the white rot basidiomycetes. The white-rot decay of wood is possible due to secretion of organic acids, secondary metabolites, and oxidoreductive metalloenzymes, heme peroxidases and laccases, encoded by divergent gene families in these fungi. The brown rot basidiomycetes obviously depend more on a non-enzymatic strategy for decomposition of wood cellulose and modification of lignin. This review gives a current ecological, genomic, and protein functional and phylogenetic perspective of the wood and lignocellulose-decaying basidiomycetous fungi.

Engineering and Applications of fungal laccases for organic synthesis

Laccases are multi-copper containing oxidases (EC 1.10.3.2), widely distributed in fungi, higher plants and bacteria. Laccase catalyses the oxidation of phenols, polyphenols and anilines by one-electron abstraction, with the concomitant reduction of oxygen to water in a four-electron transfer process. In the presence of small redox mediators, laccase offers a broader repertory of oxidations including non-phenolic substrates. Hence, fungal laccases are considered as ideal green catalysts of great biotechnological impact due to their few requirements (they only require air, and they produce water as the only by-product) and their broad substrate specificity, including direct bioelectrocatalysis.

Thus, laccases and/or laccase-mediator systems find potential applications in bioremediation, paper pulp bleaching, finishing of textiles, bio-fuel cells and more. Significantly, laccases can be used in organic synthesis, as they can perform exquisite transformations ranging from the oxidation of functional groups to the heteromolecular coupling for production of new antibiotics derivatives, or the catalysis of key steps in the synthesis of complex natural products. In this review, the application of fungal laccases and their engineering by rational design and directed evolution for organic synthesis purposes are discussed.

Molecular cloning and heterologous expression of a laccase gene from Pleurotus eryngii in free and immobilized Saccharomyces cerevisiae cells

A full length cDNA encoding an extracellular laccase was isolated by reverse transcription polymerase chain reaction from the mycelia of the mushroom Pleurotus eryngii. The isolated sequence, denoted Ery3, encodes for a mature laccase isoenzyme of 531 amino acid residues with a predicted molecular weight of 56.6 kDa. All sequence motifs, being the signature sequences used to identify the laccases, were found in the Ery3 protein sequence. The Ery3 cDNA was expressed in Saccharomyces cerevisiae and the effects of copper concentration and cultivation temperature were investigated. S. cerevisiae cells were immobilized in calcium alginate gel and the optimal immobilization parameters for the enhanced production of laccase were determined. The immobilization was most effective with 3% sodium alginate, 0.1 M calcium chloride and an initial biomass of 4.5 x 10(8) cells. The enzyme yield obtained with immobilized cells (139 mU ml(-1)) showed a 1.6-fold increase compared to the highest yield obtained with free cells. The alginate beads showed good stability and retained 84% capacity of enzyme production after seven repeated cycles of batch fermentation. The immobilization system proved to increase the proteolytic stability of the recombinant Ery3 protein. To our knowledge, this is the first report on S. cerevisiae whole-cell immobilization for recombinant laccase production.

Comparative characterization of four laccases from Trametes versicolor concerning phenolic C-C coupling and oxidation of PAHs

The laccase genes lccalpha, lccbeta, lccgamma and lccdelta encoding four isoenzymes from Trametes versicolor have been cloned and expressed in Pichia pastoris. Biochemical characterization allowed classification of these laccases into two distinct groups: Lccalpha and Lccbeta possessed higher thermal stability, but lower catalytic activity towards 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) compared to Lccgamma and Lccdelta. Activities of the laccases were quite different as well. Laccase Lccdelta showed highest phenolic C-C coupling activity with sinapic acid, but lowest oxidizing activity towards polycyclic aromatic hydrocarbons (PAHs). Highest activity towards PAHs was observed with Lccbeta. After 72h, more than 80% of fluorene, anthracene, acenaphthene and acenaphthylene were oxidized by Lccbeta in the presence of ABTS. Investigation of the structural basis of the different activities of the laccases demonstrated the impact of positions 164 and 265 in the substrate binding site on oxidation of PAHs.

Laccase production at reactor scale by filamentous fungi

Laccases have received much attention from researchers during the past decades due to their broad substrate specificity and to the fact that they use molecular oxygen as the final electron acceptor instead of hydrogen peroxide as used by peroxidases. This makes laccases highly interesting for a wide variety of processes, such as textile dye decolouration, pulp bleaching, effluent detoxification, biosensors and bioremediation. The successful application of laccases to the above-mentioned processes requires the production of large quantities of enzyme at low cost. Filamentous fungi are able to produce laccases in high amounts, however, an efficient production system at bioreactor scale is still lacking. This is mainly due to the fact that laccase production by wild-type strains of filamentous fungi is linked to secondary metabolism, which implies that the following drawbacks must be overcome: uncontrolled fungal growth, the formation of polysaccharides around mycelia and the secretion of certain compounds (i.e. proteases) that inactivate laccases. This review summarizes the current status of laccase production by wild-type strains of filamentous fungi at the bioreactor scale.

Cellulose Fiber−Enzyme Composites Fabricated through Layer-by-Layer Nanoassembly

Cellulose microfibers were coated with enzymes, laccase and urease, through layer-by-layer assembly by alternate adsorption with oppositely charged polycations. The formation of organized polyelectrolyte and enzyme multilayer films of 15-20 nm thickness was demonstrated by quartz crystal microbalance, zeta-potential analysis, and confocal laser scanning microscopy. These biocomposites retained enzymatic catalytic activity, which was proportional to the number of coated enzyme layers. For laccase-fiber composites, around 50% of its initial activity was retained after 2 weeks of storage at 4 degrees C. The synthesis of calcium carbonate microparticles on urease-fiber composites confirmed urease functionality and demonstrated its possible applications. This strategy could be employed to fabricate fiber-based composites with novel biological functions.

Cloning of a laccase gene from a novel basidiomycete Trametes sp. 420 and its heterologous expression in Pichia pastoris

The laccase gene lacD, cloned from a novel laccase-producing basidiomycete Trametes sp. 420, contained 2,052 base pairs (bp) interrupted by 8 introns. lacD displayed a relatively high homology with laccase genes from other white rot fungi, whereas the homology between lacD and laccase genes from plants, insects, or bacteria was less than 25%. A 498-amino acid peptide encoded by the lacD cDNA was heterologously expressed in the Pichia pastoris strain GS115, resulting in the highest yield of laccase (8.3 x 10(4) U/l) as determined with ABTS (2,2'-azinobis [3-ethylbenzothia-zoline-6-sulfonic acid]) as the substrate. Additionally, the enzyme activity of recombinant laccase on decolorization of some industrial dyes was assessed.