Purification of a laccase from fruiting bodies of the mushroom Pleurotus eryngii

Lessons on fruiting body morphogenesis from genomes and transcriptomes of Agaricomycetes

Fruiting bodies (sporocarps, sporophores or basidiomata) of mushroom-forming fungi (Agaricomycetes) are among the most complex structures produced by fungi. Unlike vegetative hyphae, fruiting bodies grow determinately and follow a genetically encoded developmental program that orchestrates their growth, tissue differentiation and sexual sporulation. In spite of more than a century of research, our understanding of the molecular details of fruiting body morphogenesis is still limited and a general synthesis on the genetics of this complex process is lacking. In this paper, we aim at a comprehensive identification of conserved genes related to fruiting body morphogenesis and distil novel functional hypotheses for functionally poorly characterised ones. As a result of this analysis, we report 921 conserved developmentally expressed gene families, only a few dozens of which have previously been reported to be involved in fruiting body development. Based on literature data, conserved expression patterns and functional annotations, we provide hypotheses on the potential role of these gene families in fruiting body development, yielding the most complete description of molecular processes in fruiting body morphogenesis to date. We discuss genes related to the initiation of fruiting, differentiation, growth, cell surface and cell wall, defence, transcriptional regulation as well as signal transduction. Based on these data we derive a general model of fruiting body development, which includes an early, proliferative phase that is mostly concerned with laying out the mushroom body plan (via cell division and differentiation), and a second phase of growth via cell expansion as well as meiotic events and sporulation. Altogether, our discussions cover 1 480 genes of Coprinopsis cinerea, and their orthologs in Agaricus bisporus, Cyclocybe aegerita, Armillaria ostoyae, Auriculariopsis ampla, Laccaria bicolor, Lentinula edodes, Lentinus tigrinus, Mycena kentingensis, Phanerochaete chrysosporium, Pleurotus ostreatus, and Schizophyllum commune, providing functional hypotheses for ~10 % of genes in the genomes of these species. Although experimental evidence for the role of these genes will need to be established in the future, our data provide a roadmap for guiding functional analyses of fruiting related genes in the Agaricomycetes. We anticipate that the gene compendium presented here, combined with developments in functional genomics approaches will contribute to uncovering the genetic bases of one of the most spectacular multicellular developmental processes in fungi. Citation: Nagy LG, Vonk PJ, Künzler M, Földi C, Virágh M, Ohm RA, Hennicke F, Bálint B, Csernetics Á, Hegedüs B, Hou Z, Liu XB, Nan S, M. Pareek M, Sahu N, Szathmári B, Varga T, Wu W, Yang X, Merényi Z (2023). Lessons on fruiting body morphogenesis from genomes and transcriptomes of Agaricomycetes. Studies in Mycology 104: 1-85. doi: 10.3114/sim.2022.104.01.

Purification and biochemical characterization of two laccase isoenzymes isolated from Trichoderma harzianum S7113 and its application for bisphenol A degradation

Two laccase isoenzymes (LacA and LacB) were isolated from a novel Trichoderma harzianum S7113 isolate employing ammonium sulfate precipitation, Sephadex G100, and DEAE Sepharose ion exchange chromatography. The molecular weights of the purified LacA and LacB laccases were estimated to be 63 and 48 kDa, respectively. The two isoenzymes had their optimum activities at the same temperature (50 °C), but at slightly different pH values (pH 3.0 for LacA and pH 2.5 for LacB). LacA and LacB had the same thermal stability at 40 °C and pH stability at pH 9.0. The two isoenzymes also showed a high level of specific activity toward ABTS, where the K_m values of LacA and LacB were 0.100 and 0.065 mM, whereas their V_max values were 0.603 and 0.182 µmol min^-1, respectively. LacA and LacB catalytic activity was stimulated by Mg²⁺, Zn²⁺, K⁺, and Ni²⁺, whereas it was inhibited by Hg²⁺ and Pb²⁺, β-mercaptoethanol, EDTA, and SDS, and completely inhibited by sodium azide. Our findings indicate that purified laccase has a promising capacity for bisphenol A (BPA) bioremediation across a broad pH range. This finding opens up new opportunities for the commercialization of this technique in a variety of biotechnology-based applications, particularly for removing endocrine chemicals from the environment.

Comparative study of single cultures and a consortium of white rot fungi for polychlorinated biphenyls treatment

AIMS

To evaluate the mycoremediation of polychlorinated biphenyls (PCBs) by either single cultures or binary consortia of Pleurotus pulmonarius LBM 105 and Trametes sanguinea LBM 023.

METHODS AND RESULTS

PCBs tolerance, removal capacity, toxicity reduction and ligninolytic enzyme expression were assessed when growing single culture and binary consortium of fungus in 217 mg l^-1 of a technical mixture of Aroclor 1242, 1254 and 1260 in transformer oil. A decrease in tolerance and variation in ligninolytic enzyme secretion were observed in PCB-amended solid media. Pleurotus pulmonarius LBM 105 mono-culture was able to remove up to 95·4% of PCBs, whereas binary consortium and T. sanguinea LBM 023 could biodegrade about 55% after 24 days. Significant detoxification levels were detected in all treatments by biosorption mechanism.

CONCLUSIONS

Pleurotus pulmonarius LBM 105 in single culture had the best performance regarding PCBs biodegradation and toxicity reduction. Ligninolytic enzyme secretion changed in co-culture.

SIGNIFICANCE AND IMPACT OF THE STUDY

The evaluation of PCBs bioremediation effectiveness of basidiomycetes consortium in terms of PCB removal, toxicity and ligninolytic enzyme production to unravel the differences between using individual cultures or consortium has not been reported. The results from this study enable the selection of P. pulmonarius LBM 105 mono-culture to bioremediate PCBs as it showed higher efficiency compared to binary consortium with T. sanguinea LBM 023 for potential decontamination of PCB-contaminated transformer oil.

Lectins purified from medicinal and edible mushrooms: Insights into their antiviral activity against pathogenic viruses

For thousands of years, fungi have been a valuable and promising source of therapeutic agents for treatment of various diseases. Mushroom is a macrofungus which has been cultivated worldwide for its nutritional value and medicinal applications. Several bioactive molecules were extracted from mushroom such as polysaccharides, lectins and terpenoids. Lectins are carbohydrate-binding proteins with non-immunologic origin. Lectins were classified according to their structure, origin and sugar specificity. This protein has different binding specificity with surface glycan moiety which determines its activity and therapeutic applications. A wide range of medicinal activities such as antitumor, antiviral, antimicrobial, immunomodulatory and antidiabetic were reported from sugar-binding proteins. However, glycan-binding protein from mushroom is not well explored as antiviral agent. The discovery of novel antiviral agents is a public health emergency to overcome the current pandemic and be ready for the upcoming viral pandemics. The mechanism of action of lectin against viruses targets numerous steps in viral life cycle such as viral attachment, entry and replication. This review described the history, classification, purification techniques, structure-function relationship and different therapeutic applications of mushroom lectin. In addition, we focus on the antiviral activity, purification and physicochemical characteristics of some mushroom lectins.

Purification, Biochemical Characterization and Decolorization Efficiency of Laccases from Peach and Cherry Cultures of Pleutorus eryngii: A Comparative Study

BACKGROUND

Laccases (Lacs) are used potentially in industrial and biotechnological applications such as decolorization of dyes, degradation of industrial effluents, delignification, etc. thanks to their large varieties of substrate specificities and excellent catalytic efficiencies. The efficient utilizations of Lacs in these applications mostly depend on the identifying their biochemical properties.

OBJECTIVE

The goal of this research is to investigate the purification, biochemical characterization and decolorization efficiencies of Lacs.

METHODS

Pleurotus eryngii was incubated on peach (PC) and cherry (CC) wastes under optimized solid state fermentation conditions. Then, the enzymes extracts were purified by ammonium sulfate precipitation, anion exchange chromatography, gel filtration, respectively. Lacs fractions were subjected to electrophoretic analyses as well as their structural and kinetic characteristics. Also, the effects of selected chemical agents on purified Lacs activities and determination of decolorization efficiencies were studied.

RESULTS

As the results of purification processes of Lacs from both cultures, 3.94-fold purification was obtained for PC, while it was 5.34 for CC. The electrophoretic results of purified Lacs illustrated the single bands of protein (30±1 kDa) in accordance with the results after gel filtration. The Km values of Lacs from PC and CC were respectively detected as 1.1381 and 0.329 mM for ABTS. The selected agents partially/completely inhibited Lac activities. The highest decolorization efficiencies of purified Lacs from PC and CC were separately obtained as 53 and 11.8%.

CONCLUSION

The results clearly indicated that the performances of Lacs from both cultures in decolorization application are different from each other depending their activities, biochemical and kinetic characteristics.

Structural and biochemical insights into an engineered high-redox potential laccase overproduced in Aspergillus

Fungal laccases have great potential as biocatalysts oxidizing a variety of aromatic compounds using oxygen as co-substrate. Here, the crystal structure of 7D5 laccase (PDB 6H5Y), developed in Saccharomyces cerevisiae and overproduced in Aspergillus oryzae, is compared with that of the wild type produced by basidiomycete PM1 (Coriolopsis sp.), PDB 5ANH. SAXS showed both enzymes form monomers in solution, 7D5 laccase with a more oblate geometric structure due to heavier and more heterogeneous glycosylation. The enzyme presents superior catalytic constants towards all tested substrates, with no significant change in optimal pH or redox potential. It shows noticeable high catalytic efficiency with ABTS and dimethyl-4-phenylenediamine, 7 and 32 times better than the wild type, respectively. Computational simulations demonstrated a more favorable binding and electron transfer from the substrate to the T1 copper due to the introduced mutations. PM1 laccase is exceptionally stable to thermal inactivation (t_1/2 70 °C = 1.2 h). Yet, both enzymes display outstanding structural robustness at high temperature. They keep folded during 2 h at 100 °C though, thereafter, 7D5 laccase unfolds faster. Rigidification of certain loops due to the mutations added on the protein surface would diminish the capability to absorb temperature fluctuations leading to earlier protein unfolding.

Proteolytic Activity of Edible Spruce Morchella esculenta

This study focused on the determination of non-specific proteolytic activity of edible spruce Morchella esculenta in water extract, phosphate-buffered saline (PBS) solution (pH = 7.5) extract and a suspension prepared from 200 mg DW (dry weight) of edible spruce in PBS solution (pH 7.5). A clear casein solution was used as a substrate. The absorbances were measured in quartz cuvettes at the wavelength of 280 nm against a blank with zero concentration of trypsin. Non-specific proteolytic activity was expressed as trypsin equivalents per kilogram of mushroom dry weight (mg.kg−1 DW). All of the extracts demonstrated non-specific enzymatic activity. The highest activity was observed in the PBS suspension and the lowest enzymatic activity was measured in the water extract of the Morchella esculenta fungi. The non-specific proteolytic activity decreased in the following order: PBS suspension extract (pH 7.5; 22.9 mg.kg−1 DW), followed by PBS extract (pH 7.5; 13.6 mg.kg−1 DW) and finally the water extract (10.94 mg.kg−1 DW).

Importance of a Laccase Gene (Lcc1) in the Development of Ganoderma tsugae

In this study, a novel laccase gene (Lcc1) from Ganoderma tsugae was isolated and its functions were characterized in detail. The results showed that Lcc1 has the highest expression activity during mycelium development and fruit body maturation based on the analysis of Lcc1 RNA transcripts at different developmental stages of G. tsugae. To investigate the exact contribution of Lcc1 to mycelium and fruit body development in G. tsugae, Lcc1 transgenic strains were constructed by targeted gene replacement and over-expression approaches. The results showed that the lignin degradation rate in Lcc1 deletion mutant was much lower than the degradation efficiency of the wild-type (WT), over-expression and rescue strains. The lignin degradation activity of G. tsugae is dependent on Lcc1 and the deletion of Lcc1 exerted detrimental influences on the development of mycelium branch. Furthermore, the study uncovered that Lcc1 deletion mutants generated much shorter pale grey fruit bodies, suggesting that Lcc1 contributes directly to pigmentation and stipe elongation during fruit body development in G. tsugae. The information obtained in this study provides a novel and mechanistic insight into the specific role of Lcc1 during growth and development of G. tsugae.

Extraction and characterization of proteins from banana (Musa Sapientum L) flower and evaluation of antimicrobial activities

Ultrasonic assisted alkaline extraction of protein from banana flower was optimized using response surface methodology. The extracted proteins were characterized by Fourier transform infrared spectroscopy and molecular weight distribution was determined by gel electrophoresis. The maximum protein yield of 252.25 mg/g was obtained under optimized extraction conditions: temperature 50 °C, 30 min extraction time and 1 M NaOH concentration. The alkaline extraction produced a significantly high protein yield compared to enzymatic extraction of banana flower. Chemical finger printing of proteins showed the presence of tyrosine, tryptophan and amide bonds in extracted protein. Alkaline and pepsin assisted extracted banana flower proteins showed characteristic bands at 40 and 10 kDA, respectively. The extracted proteins showed antibacterial effects against both gram positive and gram negative bacteria. The high protein content and antimicrobial activity indicate the potential applications of banana flower in the food and feed industry.

Plackett-Burman Design for rGILCC1 Laccase Activity Enhancement in Pichia pastoris: Concentrated Enzyme Kinetic Characterization

Laccases are multicopper oxidases that catalyze aromatic and nonaromatic compounds with concomitant reduction of molecular oxygen to water. They are of great interest due to their potential biotechnological applications. In this work we statistically improved culture media for recombinant GILCC1 (rGILCC1) laccase production at low scale from Ganoderma lucidum containing the construct pGAPZαA-GlucPost-Stop in Pichia pastoris. Temperature, pH stability, and kinetic parameter characterizations were determined by monitoring concentrate enzyme oxidation at different ABTS substrate concentrations. Plackett-Burman Design allowed improving enzyme activity from previous work 36.08-fold, with a laccase activity of 4.69 ± 0.39 UL⁻¹ at 168 h of culture in a 500 mL shake-flask. Concentrated rGILCC1 remained stable between 10 and 50°C and retained a residual enzymatic activity greater than 70% at 60°C and 50% at 70°C. In regard to pH stability, concentrated enzyme was more stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity greater than 55% was obtained at pH 10.0 ± 0.2. Furthermore, calculated apparent enzyme kinetic parameters were a V_max of 6.87 × 10⁻⁵ mM s⁻¹, with an apparent K_m of 5.36 × 10⁻² mM. Collectively, these important stability findings open possibilities for applications involving a wide pH and temperature ranges.

Purification and characterization of laccase from Marasmius species BBKAV79 and effective decolorization of selected textile dyes

A novel laccase-producing white-rot fungus, Marasmius sp. BBKAV79 (Genbank Accession Number-KP455496, KP455497), was isolated and subjected to purification, characterization and dye decolorization study. The purified enzyme was obtained with a specific activity of 0.226 U mg-1 protein and a final yield of 13.5 %. The enzyme was found to be a monomeric protein with a molecular mass of ~75 kDa as estimated by non-denaturing polyacrylamide gel electrophoresis (PAGE) and further confirmed with zymogram analysis. The optimal pH and temperature of the laccase was recorded to be 5.5 and 40 °C, respectively. The metal ions Hg2+ and Ag+ were found to drastically inhibit the activity of laccase at the rate of 96.6 and 96.5 %, respectively. Nevertheless, Fe3+ was found to inhibit laccase activity at 40 %. Phenylmethanesulfonyl fluoride (PMSF) strongly inhibited the laccase activity, and additives viz, sodium dodecyl sulfate (SDS), hydrogen peroxide (H2O2) and sodium chloride (NaCl) were known to follow the earlier pattern of enzyme inhibition. The values of kinetic parameters K m and V max for purified laccase were noted at 3.03 mM and 5 μmol min-1, respectively, for guaiacol as substrate. The textile dyes were decolorized at a range of 72-76 % and 88-93 % when treated with Marasmius sp. BBKAV79 and purified laccase, respectively. Based on the outcome of the present investigation, it could be, therefore, inferred that laccase isolated from Marasmius sp. BBKAV79 effectively decolorizes the textile dyes; however, the metal ions Hg2+, Ag+ and Fe3+ and agents like PMSF, SDS, H2O2 and NaCl pose an effective inhibitory potential under specified physicochemical conditions.

A Pycnoporus sanguineus laccase for denim bleaching and its comparison with an enzymatic commercial formulation

A laccase from the basidiomycete Pycnoporus sanguineus strain RVAN5 was evaluated for its ability to decolorize synthetic dyes and denim bleaching. Dye color reduction and denim bleaching were monitored at different dye concentrations and incubation times. Dye decolorization by Pycnoporus sanguineus fungal crude extract (FCE) ranged from 80 to 96% within 2-4 h at 25-65 °C. Comparable results were obtained when violuric acid (VA) was added as mediator to the FCE, however, the number of decolorized dyes increased significantly. Dye decolorization rates with VA varied of initial and final optical density (595 nm) values of 2.5-3.0 and 0.2-0.02, respectively. P. sanguineus FCE had no substantial effect on denim bleaching when used alone, notwithstanding, the mixture of FCE with VA (10 mM) showed significant denim color reduction values and considerably higher than those obtained with a bleaching enzyme from a commercial formulation; CIElab values obtained with FCE/VA mixture were of ΔL = 6.4, versus a ΔL 1.4 value obtained with an enzyme from commercial formulation.

Fungal proteinaceous compounds with multiple biological activities

Fungi comprise organisms like molds, yeasts and mushrooms. They have been used as food or medicine for a long time. A large number of fungal proteins or peptides with diverse biological activities are considered as antibacterial, antifungal, antiviral and anticancer agents. They encompass proteases, ribosome inactivating proteins, defensins, hemolysins, lectins, laccases, ribonucleases, immunomodulatory proteins, and polysaccharopeptides. The target of the present review is to update the status of the various bioactivities of these fungal proteins and peptides and discuss their therapeutic potential.

Biodegradation of phenolic compounds by Basidiomycota and its phenol oxidases: A review

The phylum Basidiomycota include organisms with enormous bioremediation potential. A variety of processes were proposed at the lab scale for using these fungi and their phenol oxidases in the degradation of phenolics. Here we present a survey of this topic using literature published mostly over the last 10 years. First, the sources of the enzymes are summarized. The laccase and tyrosinase were mainly from Trametes versicolor and Agaricus bisporus, respectively. Recently, however, new promising wild-type producers of the enzymes have emerged and a number of recombinant strains were also constructed, based mainly on yeasts or Aspergillus strains as hosts. The next part of the study summarizes the enzyme and whole-cell applications for the degradation of phenols, polyphenols, cresols, alkylphenols, naphthols, bisphenols and halogenated (bis)phenols in model mixtures or real wastewaters from the food, paper and coal industries, or municipal and hospital sewage. The enzymes were applied as free (crude or purified) enzymes or as enzymes immobilized in various supports or CLEAs, and optionally recycled or used in continuous mode. Alternatively, growing cultures or harvested mycelia were used instead. The products, which were characterized as quinones and their polymers in some cases, could be eliminated by filtration, flocculation or adsorption onto chitosan. The purity of a treated wastewater was monitored using a sensitive aquatic organism. It is concluded that low-cost sources of these enzymes should be searched for and the benefits of enzymatic, biological and physico-chemical methods could be combined to make the processes fit for industrial use.

Purification and biochemical characterization of a newly produced yellow laccase from Lentinus squarrosulus MR13

A novel yellow laccase was produced from Lentinus squarrosulus MR13 under solid state fermentation. The yellow laccase was purified by a factor of 12.67-fold by ammonium sulfate precipitation, anion exchange chromatography and gel filtration chromatography to a specific activity of 3,772.86 IU mg⁻¹. Its molecular mass was determined by SDS-PAGE and found to be 66 kDa. The activity of the enzyme was measured with 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) as substrate and found to be stable in a broad range of pH (pH 4–9). The optimum temperature of the enzyme was 40 °C. The enzyme was stable at temperatures between 25 and 55 °C and decreased rapidly when the temperature was above 65 °C. Circular dichroism spectra also supported the temperature stability of the enzyme. The K_m and V_max values of the purified yellow laccase were 0.0714 mM and 0.0091 mM min⁻¹, respectively.

Fungus Cerrena unicolor as an effective source of new antiviral, immunomodulatory, and anticancer compounds

In the report, three bioactive fractions from Cerrena unicolor: laccase (LAC), endopolysaccharides (c-EPL), and low molecular weight (ex-LMS) were tested for the first time towards their antiviral, immunostimulatory, cytotoxic and antiproliferative effect. The immunomodulatory activity was studied by means of THP-1-derived macrophages able to synthesize and secrete IL-6 and TNF-α. We used cervical carcinoma cell lines SiHa (ATCC, HTB-35) and CaSki (ATCC, CRL 1550) to determine antitumor activity and human skin fibroblasts (HSF) as a control. SiHa and L929 cell lines were used in the antiviral activity assay to propagate HHV-1 and EMCV, respectively. LAC was the most active against HSV at an early stage of viral replication, whereas the activity of laccase against EMCV was evident after incubation of the virus with LAC before and after the adsorption step. Moreover, the investigations showed that the fungal c-EPL fraction stimulated the production and secretion of TNF-α and IL-6 by THP-1-derived macrophages up to a level of 2000 pg/ml and 400 pg/ml, respectively. It was indicated for the first time that the LAC and ex-LMS fractions exhibited anticancer activity. This resulted from their cytotoxic or antiproliferative action against the investigated tumor cells at concentrations above 250 μg/ml and 10 μg/ml, respectively.

Structure and molecular evolution of multicopper blue proteins

The multicopper blue protein family, which contains cupredoxin-like domains as a structural unit, is one of the most diverse groups of proteins. This protein family is divided into two functionally different types of enzymes: multicopper oxidase and nitrite reductase. Multicopper oxidase catalyzes the oxidation of the substrate and then reduces dioxygen. The structures of many multicopper oxidases are already known, and until recently they were classified into two main groups: the three- and six-domain types. Both function as monomers and have three spectroscopically different copper sites: Types I (blue), II, and III (tri-nuclear). Nitrite reductase is a closely related protein that contains Types I and II (mono-nuclear) coppers but reduces nitrite instead of dioxygen. Nitrite reductase, which consists of two domains, forms a homotrimer. Multicopper oxidase and nitrite reductase share similar structural architectures and also contain Type I copper. Therefore, it is proposed that they have a common ancestor protein. Recently, some two-domain type multicopper oxidases have been found and their crystal structures have been determined. They have a trimeric quaternary structure and contain an active site at the molecular interface such as nitrite reductase. These results support previous hypotheses and provide an insight into the molecular evolution of multicopper blue proteins.

Bioconcentration factors and potential human health risks of heavy metals in cultivated Lentinus edodes in Chengdu, People's Republic of China

Lentinus edodes is one of the most popular edible mushrooms in the market. However, it contains heavy metals that are poisonous to humans even at trace concentrations. The concentrations and bioconcentration factors of five heavy metals in cultivated L. edodes in Chengdu were studied, and the potential health risks to local residents associated with the cultivated L. edodes consumption were evaluated. Total concentrations of cadmium (Cd), lead (Pb), chromium (Cr), arsenic (As), and mercury were determined in the fruiting bodies and the substrate from three agricultural areas. Fruiting bodies samples were collected at different growing times (2, 4, 6, and 8 days). The bioconcentration factors of heavy metals from the substrate to the fruiting bodies were estimated, and the potential health risks of local L. edodes were assessed. Because antioxidant enzymes can resist the creation of reactive oxygen species and defend against heavy metals, the activities of three antioxidant enzymes (superoxide dismutase, catalase, and peroxidase) in the fruiting bodies were also determined. A gradual change in heavy metal concentrations occurred across the growing time of the fruiting bodies. Cd transferred from the substrate to the fruiting bodies in larger concentrations than did Pb, Cr, and As. However, Chengdu residents were not exposed to significant health risks associated with consumption of local L. edodes. Nevertheless, more attention should be focused on children because of their higher sensitivity to metal pollutants.

A novel laccase with potent antiproliferative and HIV-1 reverse transcriptase inhibitory activities from mycelia of mushroom Coprinus comatus

A novel laccase was isolated and purified from fermentation mycelia of mushroom Coprinus comatus with an isolation procedure including three ion-exchange chromatography steps on DEAE-cellulose, CM-cellulose, and Q-Sepharose and one gel-filtration step by fast protein liquid chromatography on Superdex 75. The purified enzyme was a monomeric protein with a molecular weight of 64 kDa. It possessed a unique N-terminal amino acid sequence of AIGPVADLKV, which has considerably high sequence similarity with that of other fungal laccases, but is different from that of C. comatus laccases reported. The enzyme manifested an optimal pH value of 2.0 and an optimal temperature of 60^°C using 2,2′-azinobis(3-ethylbenzothiazolone-6-sulfonic acid) diammonium salt (ABTS) as the substrate. The laccase displayed, at pH 2.0 and 37^°C, K_m values of 1.59 mM towards ABTS. It potently suppressed proliferation of tumor cell lines HepG2 and MCF7, and inhibited human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) with an IC₅₀ value of 3.46 μM, 4.95 μM, and 5.85 μM, respectively, signifying that it is an antipathogenic protein.

Gene cloning and biochemical characterization of eryngase, a serine aminopeptidase of Pleurotus eryngii belonging to the family S9 peptidases

Pleurotus eryngii serine aminopeptidase that has peptide bond formation activity, redesignated as eryngase, was cloned and expressed. Eryngase has a family S9 peptidase unit in the C-terminal region having a catalytic triad of Ser, Asp, and His. In the phylogenetic relations among the subfamilies of family S9 peptidase (S9A, prolyl oligopeptidase; S9B, dipeptidyl peptidase; S9C, acylaminoacyl peptidase; S9D, glutamyl endopeptidase), eryngase existed alone in the neighbor of S9C subfamily. Mutation of the active site Ser524 of the eryngase with Ala eliminated its catalytic activity. In contrast, S524C mutant maintained low catalytic activity. Investigation of aminolysis activity using l-Phe-NH2 as a substrate showed that S524C mutant exhibited no hydrolysis reaction but synthesized a small amount of l-Phe-l-Phe-NH2 by the catalysis of aminolysis. In contrast, wild-type eryngase hydrolyzed the product of aminolysis l-Phe-l-Phe-NH2. Results show that the S524C mutant preferentially catalyzed aminolysis when on an l-Phe-NH2 substrate.

New bioactive fungal molecules with high antioxidant and antimicrobial capacity isolated from Cerrena unicolor idiophasic cultures

Three bioactive fractions, extracellular laccase (ex-LAC), crude endopolysaccharides (c-EPL), and a low molecular subfraction of secondary metabolites (ex-LMS), were isolated from the idiophasic cultures of the white rot fungus Cerrena unicolor. For the first time, we determined the antioxidant properties of these samples by chemiluminometric measurement (a) and assessment of the scavenging effect on ABTS (b) and the DPPH reduction rate (c). The highest reducing capability was found for the ex-LMS fraction: 39-90% for (a), 20-90% for (b), and 10-59% for (c) at the concentration of 6.25-800 µg/mL. The scavenging abilities of the C. unicolor c-EPL were between 36 and 70% for (a), 2 and 60% for (b), and 28 and 32% for (c) at the concentration of 6.25-800 µg/mL. A very high prooxidative potential was observed for the ex-LAC probes. The preliminary toxicity tests were done using the Microtox system and revealed the following percentage of the toxic effect against Vibrio fischeri: 85.37% for c-EPL, 50.67% for ex-LAC, and 99.8% for ex-LMS, respectively. The ex-LAC sample showed the antibacterial activity against Escherichia coli, c-EPL against Staphylococcus aureus, and ex-LMS against both bacterial strains, respectively, but the stronger inhibitory effect was exerted on S. aureus.

Decolorization of industrial synthetic dyes using engineered Pseudomonas putida cells with surface-immobilized bacterial laccase

Background

Microbial laccases are highly useful in textile effluent dye biodegradation. However, the bioavailability of cellularly expressed or purified laccases in continuous operations is usually limited by mass transfer impediment or enzyme regeneration difficulty. Therefore, this study develops a regenerable bacterial surface-displaying system for industrial synthetic dye decolorization, and evaluates its effects on independent and continuous operations.

Results

A bacterial laccase (WlacD) was engineered onto the cell surface of the solvent-tolerant bacterium Pseudomonas putida to construct a whole-cell biocatalyst. Ice nucleation protein (InaQ) anchor was employed, and the ability of 1 to 3 tandemly aligned N-terminal repeats to direct WlacD display were compared. Immobilized WlacD was determined to be surface-displayed in functional form using Western blot analysis, immunofluorescence microscopy, flow cytometry, and whole-cell enzymatic activity assay. Engineered P. putida cells were then applied to decolorize the anthraquinone dye Acid Green (AG) 25 and diazo-dye Acid Red (AR) 18. The results showed that decolorization of both dyes is Cu²⁺- and mediator-independent, with an optimum temperature of 35°C and pH of 3.0, and can be stably performed across a temperature range of 15°C to 45°C. A high activity toward AG25 (1 g/l) with relative decolorization values of 91.2% (3 h) and 97.1% (18 h), as well as high activity to AR18 (1 g/l) by 80.5% (3 h) and 89.0% (18 h), was recorded. The engineered system exhibited a comparably high activity compared with those of separate dyes in a continuous three-round shake-flask decolorization of AG25/AR18 mixed dye (each 1 g/l). No significant decline in decolorization efficacy was noted during first two-rounds but reaction equilibriums were elongated, and the residual laccase activity eventually decreased to low levels. However, the decolorizing capacity of the system was easily retrieved via a subsequent 4-h cell culturing.

Conclusions

This study demonstrates, for the first time, the methodology by which the engineered P. putida with surface-immobilized laccase was successfully used as regenerable biocatalyst for biodegrading synthetic dyes, thereby opening new perspectives in the use of biocatalysis in industrial dye biotreatment.

A laccase with HIV-1 reverse transcriptase inhibitory activity from the broth of mycelial culture of the mushroom Lentinus tigrinus

A 59 kDa laccase with inhibitory activity against HIV-1 reverse transcriptase (IC₅₀ = 2.4 μM) was isolated from the broth of mycelial culture of the mushroom Lentinus tigrinus. The isolation procedure involved ion exchange chromatography on DEAE-cellulose and CM-cellulose, and gel filtration by fast protein liquid chromatography on Superdex 75. The laccase was adsorbed on both types of ion exchangers. About 95-fold purification was achieved with a 25.9% yield of the enzyme. The procedure resulted in a specific enzyme activity of 76.6 U/mg. Its N-terminal amino acid sequence was GIPDLHDLTV, which showed little similarity to other mushroom laccase and other Lentinus tigrinus strain laccase. Its characteristics were different from previously reported laccase of other Lentinus tigrinus strain. Maximal laccase activity was observed at a pH of 4 and at a temperature of 60°C, respectively. This study yielded the information about the potentially exploitable activities of Lentinus tigrinus laccase.