The catalytic mechanism of dye-decolorizing peroxidase DyP may require the swinging movement of an aspartic acid residue

Biodegradation of malachite green by Pleurotus eryngii: a study on decolorization, mechanism, toxicity, and enzyme

The purpose of this study was to investigate the biodegradation of malachite green (MG) by Pleurotus eryngii via decolorization. This study also explored the possible mechanisms and toxicity. The results indicated that this fungus exhibited strong decolorizing potential. MG degradation based on UPLC-TOF-Triple-MS analysis revealed the formation of intermediates such as 4-(dimethylamino)benzophenone, 4-(methylamino)benzophenone, and 4-(dimethylamino)phenol. Furthermore, a significant reduction in the toxicity of the degradation products was observed using the zebrafish animal model. A newly discovered dye-decolorizing peroxidase (DyP-PE) from P. eryngii was amplified, cloned, and expressed. The purified 56.4 kDa DyP-PE strongly decolorized MG, suggesting potentially application in the bioremediation of MG pollution. Thus, the DyP-PE derived from P. eryngii may contribute to the degradation of MG.

Biochemical, Biophysical, and Structural Analysis of an Unusual DyP from the Extremophile Deinococcus radiodurans

Dye-decolorizing peroxidases (DyPs) are heme proteins with distinct structural properties and substrate specificities compared to classical peroxidases. Here, we demonstrate that DyP from the extremely radiation-resistant bacterium Deinococcus radiodurans is, like some other homologues, inactive at physiological pH. Resonance Raman (RR) spectroscopy confirms that the heme is in a six-coordinated-low-spin (6cLS) state at pH 7.5 and is thus unable to bind hydrogen peroxide. At pH 4.0, the RR spectra of the enzyme reveal the co-existence of high-spin and low-spin heme states, which corroborates catalytic activity towards H2O2 detected at lower pH. A sequence alignment with other DyPs reveals that DrDyP possesses a Methionine residue in position five in the highly conserved GXXDG motif. To analyze whether the presence of the Methionine is responsible for the lack of activity at high pH, this residue is substituted with a Glycine. UV-vis and RR spectroscopies reveal that the resulting DrDyPM190G is also in a 6cLS spin state at pH 7.5, and thus the Methionine does not affect the activity of the protein. The crystal structures of DrDyP and DrDyPM190G, determined to 2.20 and 1.53 Å resolution, respectively, nevertheless reveal interesting insights. The high-resolution structure of DrDyPM190G, obtained at pH 8.5, shows that one hydroxyl group and one water molecule are within hydrogen bonding distance to the heme and the catalytic Asparagine and Arginine. This strong ligand most likely prevents the binding of the H2O2 substrate, reinforcing questions about physiological substrates of this and other DyPs, and about the possible events that can trigger the removal of the hydroxyl group conferring catalytic activity to DrDyP.

Spectroelectrochemistry for determination of the redox potential in heme enzymes: Dye-decolorizing peroxidases

Dye-decolorizing peroxidases (DyPs) are heme-containing enzymes that are structurally unrelated to other peroxidases. Some DyPs show high potential for applications in biotechnology, which critically depends on the stability and redox potential (E°') of the enzyme. Here we provide a comparative analysis of UV-Vis- and surface-enhanced resonance Raman-based spectroelectrochemical methods for determination of the E°' of DyPs from two different organisms, and their variants generated targeting E°' upshift. We show that substituting the highly conserved Arginine in the distal side of the heme pocket by hydrophobic amino acid residues impacts the heme architecture and redox potential of DyPs from the two organisms in a very distinct manner. We demonstrate the advantages and drawbacks of the used spectroelectrochemical approaches, which is relevant for other heme proteins that contain multiple heme centers or spin populations.

Heterologous expression, purification and structural features of native Dictyostelium discoideum dye-decolorizing peroxidase bound to a natively incorporated heme

The Dictyostelium discoideum dye-decolorizing peroxidase (DdDyP) is a newly discovered peroxidase, which belongs to a unique class of heme peroxidase family that lacks homology to the known members of plant peroxidase superfamily. DdDyP catalyzes the H2O2-dependent oxidation of a wide-spectrum of substrates ranging from polycyclic dyes to lignin biomass, holding promise for potential industrial and biotechnological applications. To study the molecular mechanism of DdDyP, highly pure and functional protein with a natively incorporated heme is required, however, obtaining a functional DyP-type peroxidase with a natively bound heme is challenging and often requires addition of expensive biosynthesis precursors. Alternatively, a heme in vitro reconstitution approach followed by a chromatographic purification step to remove the excess heme is often used. Here, we show that expressing the DdDyP peroxidase in ×2 YT enriched medium at low temperature (20°C), without adding heme supplement or biosynthetic precursors, allows for a correct native incorporation of heme into the apo-protein, giving rise to a stable protein with a strong Soret peak at 402 nm. Further, we crystallized and determined the native structure of DdDyP at a resolution of 1.95 Å, which verifies the correct heme binding and its geometry. The structural analysis also reveals a binding of two water molecules at the distal site of heme plane bridging the catalytic residues (Arg239 and Asp149) of the GXXDG motif to the heme-Fe(III) via hydrogen bonds. Our results provide new insights into the geometry of native DdDyP active site and its implication on DyP catalysis.

Structural insights, biocatalytic characteristics, and application prospects of lignin-modifying enzymes for sustainable biotechnology-A review

Lignin modifying enzymes (LMEs) have gained widespread recognition in depolymerization of lignin polymers by oxidative cleavage. LMEs are a robust class of biocatalysts that include lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), laccase (LAC), and dye-decolorizing peroxidase (DyP). Members of the LMEs family act on phenolic, non-phenolic substrates and have been widely researched for valorization of lignin, oxidative cleavage of xenobiotics and phenolics. LMEs implementation in the biotechnological and industrial sectors has sparked significant attention, although its potential future applications remain underexploited. To understand the mechanism of LMEs in sustainable pollution mitigation, several studies have been undertaken to assess the feasibility of LMEs in correlating to diverse pollutants for binding and intermolecular interactions at the molecular level. However, further investigation is required to fully comprehend the underlying mechanism. In this review we presented the key structural and functional features of LMEs, including the computational aspects, as well as the advanced applications in biotechnology and industrial research. Furthermore, concluding remarks and a look ahead, the use of LMEs coupled with computational frameworks, built upon artificial intelligence (AI) and machine learning (ML), has been emphasized as a recent milestone in environmental research.

Structural insights at acidic pH of dye-decolorizing peroxidase from Bacillus subtilis

Dye-decolorizing peroxidases (DyPs), a type of heme-containing oxidoreductase enzymes, catalyze the peroxide-dependent oxidation of various industrial dyes as well as lignin and lignin model compounds. In our previous work, we have recently reported the crystal structures of class A-type DyP from Bacillus subtilis at pH 7.0 (BsDyP7), exposing the location of three binding sites for small substrates and high redox-potential substrates. The biochemical studies revealed the optimum acidic pH for enzyme activity. In the present study, the crystal structure of BsDyP at acidic pH (BsDyP4) reveals two-monomer units stabilized by intermolecular salt bridges and a hydrogen bond network in a homo-dimeric unit. Based on the monomeric structural comparison of BsDyP4 and BsDyP7, minor differences were observed in the loop regions, that is, LI (Ala64-Gln71), LII (Glu96-Lys108), LIII (Pro117-Leu124), and LIV (Leu295-Asp303). Despite these differences, BsDyP4 adopts similar heme architecture as well as three substrate-binding sites to BsDyP7. In BsDyP4, a shift in Asp187, heme pocket residue discloses the plausible reason for optimal acidic pH for BsDyP activity. This study provides insight into the structural changes in BsDyP at acidic pH, where BsDyP is biologically active.

A bacterial cold-active dye-decolorizing peroxidase from an Antarctic Pseudomonas strain

DyP (dye-decolorizing peroxidase) enzymes are hemeproteins that catalyze the H₂O₂-dependent oxidation of various molecules and also carry out lignin degradation, albeit with low activity. We identified a dyp gene in the genome of an Antarctic cold-tolerant microbe (Pseudomonas sp. AU10) that codes for a class B DyP. The recombinant protein (rDyP-AU10) was produced using Escherichia coli as a host and purified. We found that rDyP-AU10 is mainly produced as a dimer and has characteristics that resemble psychrophilic enzymes, such as high activity at low temperatures (20 °C) when using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and H₂O₂ as substrates, thermo-instability, low content of arginine, and a catalytic pocket surface larger than the DyPs from some mesophilic and thermophilic microbes. We also report the steady-state kinetic parameters of rDyP-AU10 for ABTS, hydroquinone, and ascorbate. Stopped-flow kinetics revealed that Compound I is formed with a rate constant of (2.07 ± 0.09) × 10⁶ M^-1 s^-1 at pH 5 and that this is the predominant species during turnover. The enzyme decolors dyes and modifies kraft lignin, suggesting that this enzyme may have potential use in bioremediation and in the cellulose and biofuel industries. KEY POINTS: • An Antarctic Pseudomonas strain produces a dye-decolorizing peroxidase. • The recombinant enzyme (rDyP-AU10) was produced in E. coli and purified. • rDyP-AU10 showed high activity at low temperatures. • rDyP-AU10 is potentially useful for biotechnological applications.

Fungal dye-decolorizing peroxidase diversity: roles in either intra- or extracellular processes

Abstract

Fungal dye-decolorizing peroxidases (DyPs) have found applications in the treatment of dye-contaminated industrial wastes or to improve biomass digestibility. Their roles in fungal biology are uncertain, although it has been repeatedly suggested that they could participate in lignin degradation and/or modification. Using a comprehensive set of 162 fully sequenced fungal species, we defined seven distinct fungal DyP clades on basis of a sequence similarity network. Sequences from one of these clades clearly diverged from all others, having on average the lower isoelectric points and hydropathy indices, the highest number of N-glycosylation sites, and N-terminal sequence peptides for secretion. Putative proteins from this clade are absent from brown-rot and ectomycorrhizal species that have lost the capability of degrading lignin enzymatically. They are almost exclusively present in white-rot and other saprotrophic Basidiomycota that digest lignin enzymatically, thus lending support for a specific role of DyPs from this clade in biochemical lignin modification. Additional nearly full-length fungal DyP genes were isolated from the environment by sequence capture by hybridization; they all belonged to the clade of the presumably secreted DyPs and to another related clade. We suggest focusing our attention on the presumably intracellular DyPs from the other clades, which have not been characterized thus far and could represent enzyme proteins with novel catalytic properties.

Key points

• A fungal DyP phylogeny delineates seven main sequence clades.

• Putative extracellular DyPs form a single clade of Basidiomycota sequences.

• Extracellular DyPs are associated to white-rot fungi.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-11923-0.

Direct Electrochemical Generation of Catalytically Competent Oxyferryl Species of Classes I and P Dye Decolorizing Peroxidases

This work introduces a novel way to obtain catalytically competent oxyferryl species for two different dye-decolorizing peroxidases (DyPs) in the absence of H2O2 or any other peroxide by simply applying a reductive electrochemical potential under aerobic conditions. UV-vis and resonance Raman spectroscopies show that this method yields long-lived compounds II and I for the DyPs from Bacillus subtilis (BsDyP; Class I) and Pseudomonas putida (PpDyP; Class P), respectively. Both electrochemically generated high valent intermediates are able to oxidize ABTS at both acidic and alkaline pH. Interestingly, the electrocatalytic efficiencies obtained at pH 7.6 are very similar to the values recorded for regular catalytic ABTS/H2O2 assays at the optimal pH of the enzymes, ca. 3.7. These findings pave the way for the design of DyP-based electrocatalytic reactors operable in an extended pH range without the need of harmful reagents such as H2O2.

Discovery and characterization of a novel Dyp-type peroxidase from a marine actinobacterium isolated from Trondheim fjord, Norway

A new dye-decolorizing peroxidase (DyP) was discovered through a data mining workflow based on HMMER software and profile Hidden Markov Model (HMM) using a dataset of 1200 genomes originated from a Actinobacteria strain collection isolated from Trondheim fjord. Instead of the conserved GXXDG motif known for Dyp-type peroxidases, the enzyme contains a new conserved motif EXXDG which has been not reported before. The enzyme can oxidize an anthraquinone dye Remazol Brilliant Blue R (Reactive Blue 19) and other phenolic compounds such as ferulic acid, sinapic acid, caffeic acid, 3-methylcatechol, dopamine hydrochloride, and tannic acid. The acidic pH optimum (3 to 4) and the low temperature optimum (25 °C) were confirmed using both biochemical and electrochemical assays. Kinetic and thermodynamic parameters associated with the catalytic redox center were attained by electrochemistry.

Loops around the Heme Pocket Have a Critical Role in the Function and Stability of BsDyP from Bacillus subtilis

Bacillus subtilis BsDyP belongs to class I of the dye-decolorizing peroxidase (DyP) family of enzymes and is an interesting biocatalyst due to its high redox potential, broad substrate spectrum and thermostability. This work reports the optimization of BsDyP using directed evolution for improved oxidation of 2,6-dimethoxyphenol, a model lignin-derived phenolic. After three rounds of evolution, one variant was identified displaying 7-fold higher catalytic rates and higher production yields as compared to the wild-type enzyme. The analysis of X-ray structures of the wild type and the evolved variant showed that the heme pocket is delimited by three long conserved loop regions and a small α helix where, incidentally, the mutations were inserted in the course of evolution. One loop in the proximal side of the heme pocket becomes more flexible in the evolved variant and the size of the active site cavity is increased, as well as the width of its mouth, resulting in an enhanced exposure of the heme to solvent. These conformational changes have a positive functional role in facilitating electron transfer from the substrate to the enzyme. However, they concomitantly resulted in decreasing the enzyme’s overall stability by 2 kcal mol⁻¹, indicating a trade-off between functionality and stability. Furthermore, the evolved variant exhibited slightly reduced thermal stability compared to the wild type. The obtained data indicate that understanding the role of loops close to the heme pocket in the catalysis and stability of DyPs is critical for the development of new and more powerful biocatalysts: loops can be modulated for tuning important DyP properties such as activity, specificity and stability.

First Dye-Decolorizing Peroxidase from an Ascomycetous Fungus Secreted by Xylaria grammica

Background: Fungal DyP-type peroxidases have so far been described exclusively for basidiomycetes. Moreover, peroxidases from ascomycetes that oxidize Mn²⁺ ions are yet not known. Methods: We describe here the physicochemical, biocatalytic, and molecular characterization of a DyP-type peroxidase (DyP, EC 1.11.1.19) from an ascomycetous fungus. Results: The enzyme oxidizes classic peroxidase substrates such as 2,6-DMP but also veratryl alcohol and notably Mn²⁺ to Mn³⁺ ions, suggesting a physiological function of this DyP in lignin modification. The K_M value (49 µM) indicates that Mn²⁺ ions bind with high affinity to the XgrDyP protein but their subsequent oxidation into reactive Mn³⁺ proceeds with moderate efficiency compared to MnPs and VPs. Mn²⁺ oxidation was most effective at an acidic pH (between 4.0 and 5.0) and a hypothetical surface exposed an Mn²⁺ binding site comprising three acidic amino acids (two aspartates and one glutamate) could be localized within the hypothetical XgrDyP structure. The oxidation of Mn²⁺ ions is seemingly supported by four aromatic amino acids that mediate an electron transfer from the surface to the heme center. Conclusions: Our findings shed new light on the possible involvement of DyP-type peroxidases in lignocellulose degradation, especially by fungi that lack prototypical ligninolytic class II peroxidases.

Aspartate or arginine? Validated redox state X-ray structures elucidate mechanistic subtleties of FeIV = O formation in bacterial dye-decolorizing peroxidases

Structure determination of proteins and enzymes by X-ray crystallography remains the most widely used approach to complement functional and mechanistic studies. Capturing the structures of intact redox states in metalloenzymes is critical for assigning the chemistry carried out by the metal in the catalytic cycle. Unfortunately, X-rays interact with protein crystals to generate solvated photoelectrons that can reduce redox active metals and hence change the coordination geometry and the coupled protein structure. Approaches to mitigate such site-specific radiation damage continue to be developed, but nevertheless application of such approaches to metalloenzymes in combination with mechanistic studies are often overlooked. In this review, we summarize our recent structural and kinetic studies on a set of three heme peroxidases found in the bacterium Streptomyces lividans that each belong to the dye decolourizing peroxidase (DyP) superfamily. Kinetically, each of these DyPs has a distinct reactivity with hydrogen peroxide. Through a combination of low dose synchrotron X-ray crystallography and zero dose serial femtosecond X-ray crystallography using an X-ray free electron laser (XFEL), high-resolution structures with unambiguous redox state assignment of the ferric and ferryl (Fe^IV = O) heme species have been obtained. Experiments using stopped-flow kinetics, solvent-isotope exchange and site-directed mutagenesis with this set of redox state validated DyP structures have provided the first comprehensive kinetic and structural framework for how DyPs can modulate their distal heme pocket Asp/Arg dyad to use either the Asp or the Arg to facilitate proton transfer and rate enhancement of peroxide heterolysis.

Characterization of Class V DyP-Type Peroxidase SaDyP1 from Streptomyces avermitilis and Evaluation of SaDyPs Expression in Mycelium

DyP-type peroxidases are a family of heme peroxidases named for their ability to degrade persistent anthraquinone dyes. DyP-type peroxidases are subclassified into three classes: classes P, I and V. Based on its genome sequence, Streptomyces avermitilis, eubacteria, has two genes presumed to encode class V DyP-type peroxidases and two class I genes. We have previously shown that ectopically expressed SaDyP2, a member of class V, indeed has the characteristics of a DyP-type peroxidase. In this study, we analyzed SaDyP1, a member of the same class V as SaDyP2. SaDyP1 showed high amino acid sequence identity to SaDyP2, retaining a conserved GXXDG motif and catalytic aspartate. SaDyP1 degraded anthraquinone dyes, which are specific substrates of DyP-type peroxidases but not azo dyes. In addition to such substrate specificity, SaDyP1 showed other features of DyP-type peroxidases, such as low optimal pH. Furthermore, immunoblotting using an anti-SaDyP2 polyclonal antibody revealed that SaDyP1 and/or SaDyP2 is expressed in mycelia of wild-type S. avermitilis.

Dye Decoloring Peroxidase Structure, Catalytic Properties and Applications: Current Advancement and Futurity

Dye decoloring peroxidases (DyPs) were named after their high efficiency to decolorize and degrade a wide range of dyes. DyPs are a type of heme peroxidase and are quite different from known heme peroxidases in terms of amino acid sequences, protein structure, catalytic residues, and physical and chemical properties. DyPs oxidize polycyclic dyes and phenolic compounds. Thus they find high application potentials in dealing with environmental problems. The structure and catalytic characteristics of DyPs of different families from the amino acid sequence, protein structure, and enzymatic properties, and analyzes the high-efficiency degradation ability of some DyPs in dye and lignin degradation, which vary greatly among DyPs classes. In addition, application prospects of DyPs in biomedicine and other fields are also discussed briefly. At the same time, the research strategy based on genetic engineering and synthetic biology in improving the stability and catalytic activity of DyPs are summarized along with the important industrial applications of DyPs and associated challenges. Moreover, according to the current research findings, bringing DyPs to the industrial level may require improving the catalytic efficiency of DyP, increasing production, and enhancing alkali resistance and toxicity.

Structural and Biochemical Characterization of a Dye-Decolorizing Peroxidase from Dictyostelium discoideum

A novel cytoplasmic dye-decolorizing peroxidase from Dictyostelium discoideum was investigated that oxidizes anthraquinone dyes, lignin model compounds, and general peroxidase substrates such as ABTS efficiently. Unlike related enzymes, an aspartate residue replaces the first glycine of the conserved GXXDG motif in Dictyostelium DyPA. In solution, Dictyostelium DyPA exists as a stable dimer with the side chain of Asp146 contributing to the stabilization of the dimer interface by extending the hydrogen bond network connecting two monomers. To gain mechanistic insights, we solved the Dictyostelium DyPA structures in the absence of substrate as well as in the presence of potassium cyanide and veratryl alcohol to 1.7, 1.85, and 1.6 Å resolution, respectively. The active site of Dictyostelium DyPA has a hexa-coordinated heme iron with a histidine residue at the proximal axial position and either an activated oxygen or CN^- molecule at the distal axial position. Asp149 is in an optimal conformation to accept a proton from H₂O₂ during the formation of compound I. Two potential distal solvent channels and a conserved shallow pocket leading to the heme molecule were found in Dictyostelium DyPA. Further, we identified two substrate-binding pockets per monomer in Dictyostelium DyPA at the dimer interface. Long-range electron transfer pathways associated with a hydrogen-bonding network that connects the substrate-binding sites with the heme moiety are described.

Mutational and structural analysis of an ancestral fungal dye-decolorizing peroxidase

Dye-decolorizing peroxidases (DyPs) constitute a superfamily of heme-containing peroxidases that are related neither to animal nor to plant peroxidase families. These are divided into four classes (types A, B, C, and D) based on sequence features. The active site of DyPs contains two highly conserved distal ligands, an aspartate and an arginine, the roles of which are still controversial. These ligands have mainly been studied in class A-C bacterial DyPs, largely because no effective recombinant expression systems have been developed for the fungal (D-type) DyPs. In this work, we employ ancestral sequence reconstruction (ASR) to resurrect a D-type DyP ancestor, AncDyPD-b1. Expression of AncDyPD-b1 in Escherichia coli results in large amounts of a heme-containing soluble protein and allows for the first mutagenesis study on the two distal ligands of a fungal DyP. UV-Vis and resonance Raman (RR) spectroscopic analyses, in combination with steady-state kinetics and the crystal structure, reveal fine pH-dependent details about the heme active site structure and show that both the aspartate (D222) and the arginine (R390) are crucial for hydrogen peroxide reduction. Moreover, the data indicate that these two residues play important but mechanistically different roles on the intraprotein long-range electron transfer process. DATABASE: Structural data are available in the PDB database under the accession number 7ANV.

DyP-Type Peroxidases: Recent Advances and Perspectives

In this review, we chart the major milestones in the research progress on the DyP-type peroxidase family over the past decade. Though mainly distributed among bacteria and fungi, this family actually exhibits more widespread diversity. Advanced tertiary structural analyses have revealed common and different features among members of this family. Notably, the catalytic cycle for the peroxidase activity of DyP-type peroxidases appears to be different from that of other ubiquitous heme peroxidases. DyP-type peroxidases have also been reported to possess activities in addition to peroxidase function, including hydrolase or oxidase activity. They also show various cellular distributions, functioning not only inside cells but also outside of cells. Some are also cargo proteins of encapsulin. Unique, noteworthy functions include a key role in life-cycle switching in Streptomyces and the operation of an iron transport system in Staphylococcus aureus, Bacillus subtilis and Escherichia coli. We also present several probable physiological roles of DyP-type peroxidases that reflect the widespread distribution and function of these enzymes. Lignin degradation is the most common function attributed to DyP-type peroxidases, but their activity is not high compared with that of standard lignin-degrading enzymes. From an environmental standpoint, degradation of natural antifungal anthraquinone compounds is a specific focus of DyP-type peroxidase research. Considered in its totality, the DyP-type peroxidase family offers a rich source of diverse and attractive materials for research scientists.

Characterization of a Dye-Decolorizing Peroxidase from Irpex lacteus Expressed in Escherichia coli: An Enzyme with Wide Substrate Specificity Able to Transform Lignosulfonates

A dye-decolorizing peroxidase (DyP) from Irpex lacteus was cloned and heterologously expressed as inclusion bodies in Escherichia coli. The protein was purified in one chromatographic step after its in vitro activation. It was active on ABTS, 2,6-dimethoxyphenol (DMP), and anthraquinoid and azo dyes as reported for other fungal DyPs, but it was also able to oxidize Mn²⁺ (as manganese peroxidases and versatile peroxidases) and veratryl alcohol (VA) (as lignin peroxidases and versatile peroxidases). This corroborated that I. lacteus DyPs are the only enzymes able to oxidize high redox potential dyes, VA and Mn⁺². Phylogenetic analysis grouped this enzyme with other type D-DyPs from basidiomycetes. In addition to its interest for dye decolorization, the results of the transformation of softwood and hardwood lignosulfonates suggest a putative biological role of this enzyme in the degradation of phenolic lignin.

Decolorization and biodegradation of melanoidin contained in beet molasses by an anamorphic strain of Bjerkandera adusta CCBAS930 and its mutants

We used a ligninolytic strain of the white-rot fungus B. adusta CCBAS 930 and its mutants with modified ligninolytic activity to assess their potential to remove of molasses. The analyzed strains have been shown to be able to decolorize 1% or 2% molasses solutions containing brown-colored toxic melanoidins. It was found that the decolorization process was determined by the transition to the stage of production of sporulating aerial mycelium (liquid and agar cultures) coupled with an increase in peroxidase activity, which was accompanied by a decrease in the level of melanoidin, free radicals, and phenolic compounds. Four different peroxidase activities were detected in post-culture liquids, i.e. horseradish-like (HRP-like), manganese-dependent (MnP), lignin (LiP), and versatile (VP) peroxidase activities. The HRP-like peroxidase was characterized by the highest activity. The efficiency of removal of melanoidins from a 1% molasses solution by the parental strain and the mutants was dependent on the culture method. The highest efficiency was noted in immobilized cultures (threefold higher than in the mycelium-free cultures), which was accompanied by stimulation of HRP-like peroxidase activity. Mutant 930-5 was found to be the most effective in the decolorization and decomposition of melanoidin. The HRP-like activity in the immobilized cultures of B. adusta 930-5 was 640-fold higher than in the mycelium-free cultures of the fungus. Moreover, decolorization and biodegradation of melanoidin by B. adusta CCBAS 930 and 930-5 was coupled with detoxification.

Understanding molecular enzymology of porphyrin-binding α + β barrel proteins - One fold, multiple functions

There is a high functional diversity within the structural superfamily of porphyrin-binding dimeric α + β barrel proteins. In this review we aim to analyze structural constraints of chlorite dismutases, dye-decolorizing peroxidases and coproheme decarboxylases in detail. We identify regions of structural variations within the highly conserved fold, which are most likely crucial for functional specificities. The loop linking the two ferredoxin-like domains within one subunit can be of different sequence lengths and can adopt various structural conformations, consequently defining the shape of the substrate channels and the respective active site architectures. The redox cofactor, heme b or coproheme, is oriented differently in either of the analyzed enzymes. By thoroughly dissecting available structures and discussing all available results in the context of the respective functional mechanisms of each of these redox-active enzymes, we highlight unsolved mechanistic questions in order to spark future research in this field.

Growth conditions, physiological properties, and selection of optimal parameters of biodegradation of anticancer drug daunomycin in industrial effluents by Bjerkandera adusta CCBAS930

The study characterizes the anamorphic Bjerkandera adusta strain CCBAS 930, including growth conditions, physiological properties, and enzymatic activities related to basic metabolism and specific properties coupled with the fungal secondary metabolism. It was established that the fungus grows in a wide pH range (3.5-7.5), up to 3% of salt concentration and a temperature of 5-30 °C. Media rich in natural organic components (potato, maize extracts, whey) are optimal for biomass propagation. Minimal media, containing mineral salts and glucose as well as static growth conditions, are required to obtain idiophasic mycelium, equivalent to the secondary metabolism of the fungus. Of the 7 complex C, N, and energy sources tested, the strain did not utilize only fibrous cellulose. Lipolytic activity reached the highest values of the enzymatic activities corresponding to those capabilities. The specific properties of strain B. adusta CCBAS 930 determined by the production of HRP-like peroxidase were related to the decolorization and biodegradation of anthraquinone derivative daunomycin. The decolorization of 30% of daunomycin effluents occurred most rapidly in iso-osmotic medium and non-enriched with nitrogen, containing 0.25% glucose, pH = 5.0-6.0, and 25-30 °C. In agitated cultures, the strain decolorized solutions of daunomycin by biosorption, which coincided with the inhibition of aerial mycelium production and HRP-like biosynthesis. Based on knowledge, potential and real possibilities of using the strain in bioremediation of colored industrial sewage were discussed.

Enzymatic epoxidation of cyclohexene by peroxidase immobilization on a textile and an adapted reactor design

A textile-based reaction system for new peroxidase reactions in non-native media was implemented. The epoxidation of cyclohexene by the commercial peroxidase MaxiBright® was realized with the textile-immobilized enzyme in an adapted liquid-liquid two-phase reactor. A commercially available polyester felt was used as low-price carrier and functionalized with polyvinyl amine. The covalent immobilization with glutardialdehyde lead to an enzyme loading of 0.10 g_enzyme/g_textile. The textile-based peroxidase shows a high activity retention in the presence of organic media. This catalyst is shown to enable the epoxidation of cyclohexene in various solvents as well as under neat conditions. A model reactor was produced by 3D printing which places the textile catalyst at the interphase between the liquid reaction phase and the product extracting solvent.

An Aromatic Dyad Motif in Dye Decolourising Peroxidases Has Implications for Free Radical Formation and Catalysis

Dye decolouring peroxidases (DyPs) are the most recent class of heme peroxidase to be discovered. On reacting with H₂ O₂ , DyPs form a high-valent iron(IV)-oxo species and a porphyrin radical (Compound I) followed by stepwise oxidation of an organic substrate. In the absence of substrate, the ferryl species decays to form transient protein-bound radicals on redox active amino acids. Identification of radical sites in DyPs has implications for their oxidative mechanism with substrate. Using a DyP from Streptomyces lividans, referred to as DtpA, which displays low reactivity towards synthetic dyes, activation with H₂ O₂ was explored. A Compound I EPR spectrum was detected, which in the absence of substrate decays to a protein-bound radical EPR signal. Using a newly developed version of the Tyrosyl Radical Spectra Simulation Algorithm, the radical EPR signal was shown to arise from a pristine tyrosyl radical and not a mixed Trp/Tyr radical that has been widely reported in DyP members exhibiting high activity with synthetic dyes. The radical site was identified as Tyr374, with kinetic studies inferring that although Tyr374 is not on the electron-transfer pathway from the dye RB19, its replacement with a Phe does severely compromise activity with other organic substrates. These findings hint at the possibility that alternative electron-transfer pathways for substrate oxidation are operative within the DyP family. In this context, a role for a highly conserved aromatic dyad motif is discussed.

A novel bacterial class V dye-decolourizing peroxidase from the extremophile Deinococcus radiodurans: cloning, expression optimization, purification, crystallization, initial characterization and X-ray diffraction analysis

Deinococcus radiodurans is a bacterium with extreme resistance to desiccation and radiation. The resistance mechanism is unknown, but an efficient reactive oxygen species (ROS) scavenging system and DNA-repair and DNA-protection mechanisms are believed to play important roles. Here, the cloning and small- and medium-scale expression tests of a novel dye-decolourizing peroxidase from D. radiodurans (DrDyP) using three different Escherichia coli strains and three different temperatures in order to identify the optimum conditions for the expression of recombinant DrDyP are presented. The best expression conditions were used for large-scale expression and yielded ∼10 mg recombinant DrDyP per litre of culture after purification. Initial characterization experiments demonstrated unusual features with regard to the haem spin state, which motivated the crystallization experiment. The obtained crystals were used for data collection and diffracted to 2.2 Å resolution. The crystals belonged to the trigonal space group P31 or P32, with unit-cell parameters a = b = 64.13, c = 111.32 Å, and are predicted to contain one DrDyP molecule per asymmetric unit. Structure determination by molecular replacement using previously determined structures of dye-decolourizing peroxidases with ∼30% sequence identity at ∼2 Å resolution as templates are ongoing.

Distinguishing Active Site Characteristics of Chlorite Dismutases with Their Cyanide Complexes

O2-evolving chlorite dismutases (Clds) efficiently convert chlorite (ClO2-) to O2 and Cl-. Dechloromonas aromatica Cld ( DaCld) is a highly active chlorite-decomposing homopentameric enzyme, typical of Clds found in perchlorate- and chlorate-respiring bacteria. The Gram-negative, human pathogen Klebsiella pneumoniae contains a homodimeric Cld ( KpCld) that also decomposes ClO2-, albeit with an activity 10-fold lower and a turnover number lower than those of DaCld. The interactions between the distal pocket and heme ligand of the DaCld and KpCld active sites have been probed via kinetic, thermodynamic, and spectroscopic behaviors of their cyanide complexes for insight into active site characteristics that are deterministic for chlorite decomposition. At 4.7 × 10-9 M, the KD for the KpCld-CN- complex is 2 orders of magnitude smaller than that of DaCld-CN- and indicates an affinity for CN- that is greater than that of most heme proteins. The difference in CN- affinity between Kp- and DaClds is predominantly due to differences in koff. The kinetics of binding of cyanide to DaCld, DaCld(R183Q), and KpCld between pH 4 and 8.5 corroborate the importance of distal Arg183 and a p Ka of ∼7 in stabilizing complexes of anionic ligands, including the substrate. The Fe-C stretching and FeCN bending modes of the DaCld-CN- (νFe-C, 441 cm-1; δFeCN, 396 cm-1) and KpCld-CN- (νFe-C, 441 cm-1; δFeCN, 356 cm-1) complexes reveal differences in their FeCN angle, which suggest different distal pocket interactions with their bound cyanide. Conformational differences in their catalytic sites are also reported by the single ferrous KpCld carbonyl complex, which is in contrast to the two conformers observed for DaCld-CO.

Identification, heterologous expression and characterization of a dye-decolorizing peroxidase of Pleurotus sapidus

The coding sequence of a peroxidase from the secretome of Pleurotus sapidus was cloned from a cDNA library. Bioinformatic analyses revealed an open reading frame of 1551 bp corresponding to a primary translation product of 516 amino acids. The DyP-type peroxidase was heterologously produced in Trichoderma reesei with an activity of 55,000 U L^-1. The enzyme was purified from the culture supernatant, biochemically characterized and the kinetic parameters were determined. The enzyme has an N-terminal signal peptide composed of 62 amino acids. Analysis by Blue Native PAGE and activity staining with ABTS, as well as gel filtration chromatography showed the native dimeric state of the enzyme (115 kDa). Analysis of the substrate range revealed that the recombinant enzyme catalyzes, in addition to the conversion of some classic peroxidase substrates such as 2,2'-azino-bis(3-ethylthiazoline-6-sulfonate) and substituted phenols like 2,6-dimethoxyphenol, also the decolorization of the anthraquinonic dye Reactive Blue 5. The enzyme also catalyzes bleaching of natural colorants such as β-carotene and annatto. Surprisingly, β-carotene was transformed in the presence and absence of H₂O₂ by rPsaDyP, however enzyme activity was increased by the addition of H₂O₂. This indicates that the rPsaDyP has an oxidase function in addition to a peroxidase activity. As a consequence of the high affinity to the characteristic substrate Reactive Blue 5 the rPsaDyP belongs functionally to the dyp-type peroxidase family.

Crystal structure and biochemical features of dye-decolorizing peroxidase YfeX from Escherichia coli O157 Asp143 and Arg232 play divergent roles toward different substrates

YfeX from Escherichia coli O157 is a bacterial dye-decolorizing peroxidase that represents both dye-decoloring activity and typical peroxidase activity. We reported the crystal structure of YfeX bound to heme at 2.09 Å resolution. The YfeX monomer resembles a ferredoxin-like fold and contains two domains. The three conserved residues surrounding the heme group are His²¹⁵, Asp¹⁴³ and Arg²³². His²¹⁵ functions as the proximal axial ligand of the heme iron atom. Biochemical data show that the catalytic significance of the conserved Asp¹⁴³ and Arg²³² depends on the substrate types and that YfeX may adopt various catalytic mechanisms toward divergent substrates. In addition, it is observed that an access tunnel spans from the protein molecular surface to the heme distal region, it serves as the passageway for the entrance and binding of the H₂O₂.

Biotechnological and Biochemical Utilization of Lignin

This chapter provides an overview of the biosynthesis and structure of lignin. Moreover, examples of the commercial use of lignin and its promising future implementation are briefly described. Many applications are still hampered by the properties of technical lignins. Thus, the major challenge is the conversion of lignins into suitable building blocks or aromatics in order to open up new avenues for the usage of this renewable raw material. This chapter focuses on details about natural lignin degradation by fungi and bacteria, which harbor potential tools for lignin degradation and modification, which might help to develop eco-efficient processes for lignin utilization.

Heterolytic OO bond cleavage: Functional role of Glu113 during bis-Fe(IV) formation in MauG

The diheme enzyme MauG utilizes H₂O₂ to perform oxidative posttranslational modification on a protein substrate. A bis-Fe(IV) species of MauG was previously identified as a key intermediate in this reaction. Heterolytic cleavage of the OO bond of H₂O₂ drives the formation of the bis-Fe(IV) intermediate. In this work, we tested a hypothesis that a glutamate residue, Glu113 in the distal pocket of the pentacoordinate heme of MauG, facilitates heterolytic OO bond cleavage, thereby leading to bis-Fe(IV) formation. This hypothesis was proposed based on sequence alignment and structural comparison with other H₂O₂-utilizing hemoenzymes, especially those from the diheme enzyme superfamily that MauG belongs to. Electron paramagnetic resonance (EPR) characterization of the reaction between MauG and H₂O₂ revealed that mutation of Glu113 inhibited heterolytic OO bond cleavage, in agreement with our hypothesis. This result was further confirmed by the HPLC study in which an analog of H₂O₂, cumene hydroperoxide, was used to probe the pattern of OO bond cleavage. Together, our data suggest that Glu113 functions as an acid-base catalyst to assist heterolytic OO bond cleavage during the early stage of the catalytic reaction. This work advances our mechanistic understanding of the H₂O₂-activation process during bis-Fe(IV) formation in MauG.

Chemistry and Molecular Dynamics Simulations of Heme b-HemQ and Coproheme-HemQ

Recently, a novel pathway for heme b biosynthesis in Gram-positive bacteria has been proposed. The final poorly understood step is catalyzed by an enzyme called HemQ and includes two decarboxylation reactions leading from coproheme to heme b. Coproheme has been suggested to act as both substrate and redox active cofactor in this reaction. In the study presented here, we focus on HemQs from Listeria monocytogenes (LmHemQ) and Staphylococcus aureus (SaHemQ) recombinantly produced as apoproteins in Escherichia coli. We demonstrate the rapid and two-phase uptake of coproheme by both apo forms and the significant differences in thermal stability of the apo forms, coproheme-HemQ and heme b-HemQ. Reduction of ferric high-spin coproheme-HemQ to the ferrous form is shown to be enthalpically favored but entropically disfavored with standard reduction potentials of -205 ± 3 mV for LmHemQ and -207 ± 3 mV for SaHemQ versus the standard hydrogen electrode at pH 7.0. Redox thermodynamics suggests the presence of a pronounced H-bonding network and restricted solvent mobility in the heme cavity. Binding of cyanide to the sixth coproheme position is monophasic but relatively slow (∼1 × 10(4) M(-1) s(-1)). On the basis of the available structures of apo-HemQ and modeling of both loaded forms, molecular dynamics simulation allowed analysis of the interaction of coproheme and heme b with the protein as well as the role of the flexibility at the proximal heme cavity and the substrate access channel for coproheme binding and heme b release. Obtained data are discussed with respect to the proposed function of HemQ in monoderm bacteria.

Anabaena sp. DyP-type peroxidase is a tetramer consisting of two asymmetric dimers

DyP-type peroxidases are a newly discovered family of heme peroxidases distributed from prokaryotes to eukaryotes. Recently, using a structure-based sequence alignment, we proposed the new classes, P, I and V, as substitutes for classes A, B, C, and D [Arch Biochem Biophys 2015;574:49-55]. Although many class V enzymes from eukaryotes have been characterized, only two from prokaryotes have been reported. Here, we show the crystal structure of one of these two enzymes, Anabaena sp. DyP-type peroxidase (AnaPX). AnaPX is tetramer formed from Cys224-Cys224 disulfide-linked dimers. The tetramer of wild-type AnaPX was stable at all salt concentrations tested. In contrast, the C224A mutant showed salt concentration-dependent oligomeric states: in 600 mM NaCl, it maintained a tetrameric structure, whereas in the absence of salt, it dissociated into monomers, leading to a reduction in thermostability. Although the tetramer exhibits non-crystallographic, 2-fold symmetry in the asymmetric unit, two subunits forming the Cys224-Cys224 disulfide-linked dimer are related by 165° rotation. This asymmetry creates an opening to cavities facing the inside of the tetramer, providing a pathway for hydrogen peroxide access. Finally, a phylogenetic analysis using structure-based sequence alignments showed that class V enzymes from prokaryotes, including AnaPX, are phylogenetically closely related to class V enzymes from eukaryotes.

Substrate, product, and cofactor: The extraordinarily flexible relationship between the CDE superfamily and heme

PFam Clan 0032, also known as the CDE superfamily, is a diverse group of at least 20 protein families sharing a common α,β-barrel domain. Of these, six different groups bind heme inside the barrel's interior, using it alternately as a cofactor, substrate, or product. Focusing on these six, an integrated picture of structure, sequence, taxonomy, and mechanism is presented here, detailing how a single structural motif might be able to mediate such an array of functions with one of nature's most important small molecules.

Description of the first fungal dye-decolorizing peroxidase oxidizing manganese(II)

Two phylogenetically divergent genes of the new family of dye-decolorizing peroxidases (DyPs) were found during comparison of the four DyP genes identified in the Pleurotus ostreatus genome with over 200 DyP genes from other basidiomycete genomes. The heterologously expressed enzymes (Pleos-DyP1 and Pleos-DyP4, following the genome nomenclature) efficiently oxidize anthraquinoid dyes (such as Reactive Blue 19), which are characteristic DyP substrates, as well as low redox-potential dyes (such as 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)) and substituted phenols. However, only Pleos-DyP4 oxidizes the high redox-potential dye Reactive Black 5, at the same time that it displays high thermal and pH stability. Unexpectedly, both enzymes also oxidize Mn²⁺ to Mn³⁺, albeit with very different catalytic efficiencies. Pleos-DyP4 presents a Mn²⁺ turnover (56 s⁻¹) nearly in the same order of the two other Mn²⁺-oxidizing peroxidase families identified in the P. ostreatus genome: manganese peroxidases (100 s⁻¹ average turnover) and versatile peroxidases (145 s⁻¹ average turnover), whose genes were also heterologously expressed. Oxidation of Mn²⁺ has been reported for an Amycolatopsis DyP (24 s⁻¹) and claimed for other bacterial DyPs, albeit with lower activities, but this is the first time that Mn²⁺ oxidation is reported for a fungal DyP. Interestingly, Pleos-DyP4 (together with ligninolytic peroxidases) is detected in the secretome of P. ostreatus grown on different lignocellulosic substrates. It is suggested that generation of Mn³⁺ oxidizers plays a role in the P. ostreatus white-rot lifestyle since three different families of Mn²⁺-oxidizing peroxidase genes are present in its genome being expressed during lignocellulose degradation.

An integrated view of redox and catalytic properties of B-type PpDyP from Pseudomonas putida MET94 and its distal variants

PpDyP from Pseudomonas putida MET94 is an extremely versatile B-type dye-decolourising peroxidase (DyP) capable of efficient oxidation of a wide range of anthraquinonic and azo dyes, phenolic substrates, the non-phenolic veratryl alcohol and even manganese and ferrous ions. In reaction with H2O2 it forms a stable Compound I at a rate of (1.4±0.3)×10(6)M(-1)s(-1), comparable to those of classical peroxidases and other DyPs. We provide the first report of standard redox potential (E(0')) of the Compound I/Native redox couple in a DyP-type peroxidase. The value of E(0')Cpd I/N=1.10±0.04 (V) is similar to those found in peroxidases from the mammalian superfamily but higher than in peroxidases from the plant superfamily. Site-directed mutagenesis has been used to investigate the role of conserved distal residues, i.e. to replace aspartate 132 by asparagine, and arginine 214 and asparagine 136 by leucine. The structural, redox and catalytic properties of variants are addressed by spectroscopic, electrochemical and kinetic measurements. Our data point to the importance of the distal arginine in the catalytic mechanism of PpDyP, as also observed in DyPB from Rhodococcus jostii RHA1 but not in DyPs from the A and D subfamilies. This work reinforces the idea of existence of mechanistic variations among members of the different sub-families of DyPs with direct implications for their enzymatic properties and potential for biotechnological applications.

A dye-decolorizing peroxidase from Bacillus subtilis exhibiting substrate-dependent optimum temperature for dyes and β-ether lignin dimer

In the biorefinery using lignocellulosic biomass as feedstock, pretreatment to breakdown or loosen lignin is important step and various approaches have been conducted. For biological pretreatment, we screened Bacillus subtilis KCTC2023 as a potential lignin-degrading bacterium based on veratryl alcohol (VA) oxidation test and the putative heme-containing dye-decolorizing peroxidase was found in the genome of B. subtilis KCTC2023. The peroxidase from B. subtilis KCTC2023 (BsDyP) was capable of oxidizing various substrates and atypically exhibits substrate-dependent optimum temperature: 30°C for dyes (Reactive Blue19 and Reactive Black5) and 50°C for high redox potential substrates (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid [ABTS], VA, and veratryl glycerol-β-guaiacyl ether [VGE]) over +1.0 V vs. normal hydrogen electrode. At 50°C, optimum temperature for high redox potential substrates, BsDyP not only showed the highest VA oxidation activity (0.13 Umg⁻¹) among the previously reported bacterial peroxidases but also successfully achieved VGE decomposition by cleaving C_α-C_β bond in the absence of any oxidative mediator with a specific activity of 0.086 Umg⁻¹ and a conversion rate of 53.5%. Based on our results, BsDyP was identified as the first bacterial peroxidase capable of oxidizing high redox potential lignin-related model compounds, especially VGE, revealing a previously unknown versatility of lignin degrading biocatalyst in nature.

A structural and functional perspective of DyP-type peroxidase family

Dye-decolorizing peroxidase from the basidiomycete Bjerkandera adusta Dec 1 (DyP) is a heme peroxidase. This name reflects its ability to degrade several anthraquinone dyes. The substrate specificity, the amino acid sequence, and the tertiary structure of DyP are different from those of the other heme peroxidase (super)families. Therefore, many proteins showing the similar amino acid sequences to that of DyP are called DyP-type peroxidase which is a new family of heme peroxidase identified in 2007. In fact, all structures of this family show a similar structure fold. However, this family includes many proteins whose amino acid sequence identity to DyP is lower than 15% and/or whose catalytic efficiency (kcat/Km) is a few orders of magnitude less than that of DyP. A protein showing an activity different from peroxidase activity (dechelatase activity) has been also reported. In addition, the precise physiological roles of DyP-type peroxidases are unknown. These facts raise a question of whether calling this family DyP-type peroxidase is suitable. Here, we review the differences and similarities of structure and function among this family and propose the reasonable new classification of DyP-type peroxidase family, that is, class P, I and V. In this contribution, we discuss the adequacy of this family name.

Basidiomycete DyPs: Genomic diversity, structural-functional aspects, reaction mechanism and environmental significance

The first enzyme with dye-decolorizing peroxidase (DyP) activity was described in 1999 from an arthroconidial culture of the fungus Bjerkandera adusta. However, the first DyP sequence had been deposited three years before, as a peroxidase gene from a culture of an unidentified fungus of the family Polyporaceae (probably Irpex lacteus). Since the first description, fewer than ten basidiomycete DyPs have been purified and characterized, but a large number of sequences are available from genomes. DyPs share a general fold and heme location with chlorite dismutases and other DyP-type related proteins (such as Escherichia coli EfeB), forming the CDE superfamily. Taking into account the lack of an evolutionary relationship with the catalase-peroxidase superfamily, the observed heme pocket similarities must be considered as a convergent type of evolution to provide similar reactivity to the enzyme cofactor. Studies on the Auricularia auricula-judae DyP showed that high-turnover oxidation of anthraquinone type and other DyP substrates occurs via long-range electron transfer from an exposed tryptophan (Trp377, conserved in most basidiomycete DyPs), whose catalytic radical was identified in the H2O2-activated enzyme. The existence of accessory oxidation sites in DyP is suggested by the residual activity observed after site-directed mutagenesis of the above tryptophan. DyP degradation of substituted anthraquinone dyes (such as Reactive Blue 5) most probably proceeds via typical one-electron peroxidase oxidations and product breakdown without a DyP-catalyzed hydrolase reaction. Although various DyPs are able to break down phenolic lignin model dimers, and basidiomycete DyPs also present marginal activity on nonphenolic dimers, a significant contribution to lignin degradation is unlikely because of the low activity on high redox-potential substrates.

Carotene-degrading activities from Bjerkandera adusta possess an application in detergent industries

Four extracellular enzymes, a versatile peroxidase, a manganese peroxidase, a dye-decolorizing peroxidase and a lignin peroxidase were discovered in liquid cultures of the basidiomycete Bjerkandera adusta. All of them cleaved β-carotene effectively. Expression was enhanced in the presence of β-carotene or Coomassie Brilliant Blue and peaked after 7-9 days. The monomeric proteins were purified by ion exchange and size exclusion chromatography and exhibited molecular masses of 41, 43, 51 and 43 kDa, respectively. The coding sequences showed homologies from 61 to 89 % to peroxidases from other basidiomycetes. The novel enzymes retained strong activity even in the absence of hydrogen peroxide and at alkaline pH. De-staining of fabrics using detergent-tolerant enzymes may help to save the most important bio-resources, energy and water, in washing processes and led to green processes in textile cleaning.

The catalytic mechanism of A-type dye-decolourising peroxidase BsDyP: neither aspartate nor arginine is individually essential for peroxidase activity

BsDyP from Bacillus subtilis belongs to the new dye-decolourising peroxidase (DyP) family. Here, we use transient kinetics to provide details on the catalytic cycle of BsDyP.