Suicide inactivation of peroxidases and the challenge of engineering more robust enzymes

Structure-function characterization of two enzymes from novel subfamilies of manganese peroxidases secreted by the lignocellulose-degrading Agaricales fungi Agrocybe pediades and Cyathus striatus

BACKGROUND

Manganese peroxidases (MnPs) are, together with lignin peroxidases and versatile peroxidases, key elements of the enzymatic machineries secreted by white-rot fungi to degrade lignin, thus providing access to cellulose and hemicellulose in plant cell walls. A recent genomic analysis of 52 Agaricomycetes species revealed the existence of novel MnP subfamilies differing in the amino-acid residues that constitute the manganese oxidation site. Following this in silico analysis, a comprehensive structure-function study is needed to understand how these enzymes work and contribute to transform the lignin macromolecule.

RESULTS

Two MnPs belonging to the subfamilies recently classified as MnP-DGD and MnP-ESD-referred to as Ape-MnP1 and Cst-MnP1, respectively-were identified as the primary peroxidases secreted by the Agaricales species Agrocybe pediades and Cyathus striatus when growing on lignocellulosic substrates. Following heterologous expression and in vitro activation, their biochemical characterization confirmed that these enzymes are active MnPs. However, crystal structure and mutagenesis studies revealed manganese coordination spheres different from those expected after their initial classification. Specifically, a glutamine residue (Gln333) in the C-terminal tail of Ape-MnP1 was found to be involved in manganese binding, along with Asp35 and Asp177, while Cst-MnP1 counts only two amino acids (Glu36 and Asp176), instead of three, to function as a MnP. These findings led to the renaming of these subfamilies as MnP-DDQ and MnP-ED and to re-evaluate their evolutionary origin. Both enzymes were also able to directly oxidize lignin-derived phenolic compounds, as seen for other short MnPs. Importantly, size-exclusion chromatography analyses showed that both enzymes cause changes in polymeric lignin in the presence of manganese, suggesting their relevance in lignocellulose transformation.

CONCLUSIONS

Understanding the mechanisms used by basidiomycetes to degrade lignin is of particular relevance to comprehend carbon cycle in nature and to design biotechnological tools for the industrial use of plant biomass. Here, we provide the first structure-function characterization of two novel MnP subfamilies present in Agaricales mushrooms, elucidating the main residues involved in catalysis and demonstrating their ability to modify the lignin macromolecule.

Dye-decolorizing peroxidase of Thermobifida halotolerance displays complex kinetics with both substrate inhibition and apparent positive cooperativity

Dye-decolorizing peroxidases (DyPs) have been intensively investigated for the purpose of industrial dye decolourization and lignin degradation. Unfortunately, the characterization of these peroxidases is hampered by their non-Michaelis-Menten kinetics, exemplified by substrate inhibition and/or positive cooperativity. Although often observed, the underlying mechanisms behind the unusual kinetics of DyPs are poorly understood. Here we studied the kinetics of the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), hydroquinones, and anthraquinone dyes by DyP from the bacterium Thermobifida halotolerans (ThDyP) and solved its crystal structure. We also provide rate equations for different kinetic mechanisms explaining the complex kinetics of heme peroxidases. Kinetic studies along with the analysis of the structure of ThDyP suggest that the substrate inhibition is caused by the non-productive binding of ABTS to the enzyme resting state. Strong irreversible inactivation of ThDyP by H2O2 in the absence of ABTS suggests that the substrate inhibition by H2O2 may be caused by the non-productive binding of H2O2 to compound I. Positive cooperativity was observed only with the oxidation of ABTS but not with the two electron-donating substrates. Although the conventional mechanism of cooperativity cannot be excluded, we propose that the oxidation of ABTS assumes the simultaneous binding of two ABTS molecules to reduce compound I to the enzyme resting state, and this causes the apparent positive cooperativity.

Targeting deoxynivalenol for degradation by a chimeric manganese peroxidase/glutathione system

The manganese peroxidase (MnP) can degrade multiple mycotoxins including deoxynivalenol (DON) efficiently; however, the lignin components abundant in foods and feeds were discovered to interfere with DON catalysis. Herein, using MnP from Ceriporiopsis subvermispora (CsMnP) as a model, it was demonstrated that desired catalysis of DON, but not futile reactions with lignin, in the reaction systems containing feeds could be achieved by engineering MnP and supplementing with a boosting reactant. Specifically, two successive strategies (including the fusion of CsMnP to a DON-recognizing ScFv and identification of glutathione as a specific targeting enhancer) were combined to overcome the lignin competition, which together resulted into elevation of the degradation rate from 2.5% to as high as 82.7% in the feeds. The method to construct a targeting MnP and fortify it with an additional enhancer could be similarly applied to catalyze the many other mycotoxins with yet unknown responsive biocatalysts.

Long-term continuous degradation of carbon nanotubes by a bacteria-driven Fenton reaction

Very few bacteria are known that can degrade carbon nanotubes (CNTs), and the only known degradation mechanism is a Fenton reaction driven by Labrys sp. WJW with siderophores, which only occurs under iron-deficient conditions. No useful information is available on the degradation rates or long-term stability and continuity of the degradation reaction although several months or more are needed for CNT degradation. In this study, we investigated long-term continuous degradation of oxidized (carboxylated) single-walled CNTs (O-SWCNTs) using bacteria of the genus Shewanella. These bacteria are widely present in the environment and can drive the Fenton reaction by alternating anaerobic-aerobic growth conditions under more general environmental conditions. We first examined the effect of O-SWCNTs on the growth of S. oneidensis MR-1, and it was revealed that O-SWCNTs promote growth up to 30 μg/mL but inhibit growth at 40 μg/mL and above. Then, S. oneidensis MR-1 was subjected to incubation cycles consisting of 21-h anaerobic and 3-h aerobic periods in the presence of 30 μg/mL O-SWCNTs and 10 mM Fe(III) citrate. We determined key factors that help prolong the bacteria-driven Fenton reaction and finally achieved long-term continuous degradation of O-SWCNTs over 90 d. By maintaining a near neutral pH and replenishing Fe(III) citrate at 60 d, a degraded fraction of 56.3% was reached. S. oneidensis MR-1 produces Fe(II) from Fe(III) citrate, a final electron acceptor for anaerobic respiration during the anaerobic period. Then, ·OH is generated through the Fenton reaction by Fe(II) and H2O2 produced by MR-1 during the aerobic period. ·OH was responsible for O-SWCNT degradation, which was inhibited by scavengers of H2O2 and ·OH. Raman spectroscopy and X-ray photoelectron spectroscopy showed that the graphitic structure in O-SWCNTs was oxidized, and electron microscopy showed that long CNT fibers initially aggregated and became short and isolated during degradation. Since Shewanella spp. and iron are ubiquitous in the environment, this study suggests that a Fenton reaction driven by this genus is applicable to the degradation of CNTs under a wide range of conditions and will help researchers develop novel methods for waste treatment and environmental bioremediation against CNTs.

Biodegradation mechanisms of polycyclic aromatic hydrocarbons: Combination of instrumental analysis and theoretical calculation

Polycyclic aromatic hydrocarbons (PAHs) are a common class of petroleum hydrocarbons, widely encountered in both environment and industrial pollution sources. Owing to their toxicity, environmental persistence, and potential bioaccumulation properties, a mounting interest has been kindled in addressing the remediation of PAHs. Biodegradation is widely employed for the removal and remediation of PAHs due to its low cost, lack of second-contamination and ease of operation. This paper reviews the degradation efficiency of degradation and the underlying mechanisms exhibited by algae, bacteria, and fungi in remediation. Additionally, it delved into the application of modern instrumental analysis techniques and theoretical investigations in the realm of PAH degradation. Advanced instrumental analysis methods such as mass spectrometry provide a powerful tool for identifying intermediates and metabolites throughout the degradation process. Meanwhile, theoretical calculations could guide the optimization of degradation processes by revealing the reaction mechanisms and energy changes in PAH degradation. The combined use of instrumental analysis and theoretical calculations allows for a comprehensive understanding of the degradation mechanisms of PAHs and provides new insights and approaches for the development of environmental remediation technologies.

Production of Extracellular Enzymes by Lentinula edodes Strains in Solid-State Fermentation on Lignocellulosic Biomass Sterilized by Physical and Chemical Methods

Two methods of sterilization of lignocellulosic biomass were performed in this study. Eucalypt waste (EW) supplemented with rice bran (RB) was added in the proportions 80:20 and 90:10 in dry weight. The compositions were sterilized by physical method (autoclaving) and by chemical method (H2O2). The production of extracellular enzymes by Lentinula edodes strains was compared within the two methods. Inactivation of catalase present in RB was achieved with 250 mM H2O2. The use of H2O2, when compared by physical method, favored high production of hydrolytic enzymes such as endoglucanase (1,600 IU/kg), twofold higher, β-glucosidase (1,000 IU/kg), fivefold higher, xylanase (55,000 IU/kg), threefold higher and β-xylosidase (225 IU/kg), similar results. Oxidative enzymes, MnP and laccase, were produced within a different profile between strains, with shorter times for laccase (2,200 IU/kg) by SJC in 45 days and MnP (2,000 IU/kg) by CCB-514 in 30 days. High production of extracellular enzymes is achieved by the use of the chemical method of sterilization of lignocellulosic biomass; in addition to no energy consumption, this process is carried out in a shorter execution time when compared to the physical process. The use of H2O2 in sterilization does not produce toxic compounds from the degradation of hemicellulose and cellulose such as furfural and hydroxy-methyl-furfural that cause inhibition of microorganisms and enzymes.

Electrochemical transformations catalyzed by cytochrome P450s and peroxidases

Cytochrome P450s (Cyt P450s) and peroxidases are enzymes featuring iron heme cofactors that have wide applicability as biocatalysts in chemical syntheses. Cyt P450s are a family of monooxygenases that oxidize fatty acids, steroids, and xenobiotics, synthesize hormones, and convert drugs and other chemicals to metabolites. Peroxidases are involved in breaking down hydrogen peroxide and can oxidize organic compounds during this process. Both heme-containing enzymes utilize active Fe^IVO intermediates to oxidize reactants. By incorporating these enzymes in stable thin films on electrodes, Cyt P450s and peroxidases can accept electrons from an electrode, albeit by different mechanisms, and catalyze organic transformations in a feasible and cost-effective way. This is an advantageous approach, often called bioelectrocatalysis, compared to their biological pathways in solution that require expensive biochemical reductants such as NADPH or additional enzymes to recycle NADPH for Cyt P450s. Bioelectrocatalysis also serves as an ex situ platform to investigate metabolism of drugs and bio-relevant chemicals. In this paper we review biocatalytic electrochemical reactions using Cyt P450s including C-H activation, S-oxidation, epoxidation, N-hydroxylation, and oxidative N-, and O-dealkylation; as well as reactions catalyzed by peroxidases including synthetically important oxidations of organic compounds. Design aspects of these bioelectrocatalytic reactions are presented and discussed, including enzyme film formation on electrodes, temperature, pH, solvents, and activation of the enzymes. Finally, we discuss challenges and future perspective of these two important bioelectrocatalytic systems.

Peroxidase-induced C-N bond formation via nitroso ene and Diels-Alder reactions

The formation of new carbon-nitrogen bonds is indisputably one of the most important tasks in synthetic organic chemistry. Here, nitroso compounds offer a highly interesting reactivity that complements traditional amination strategies, allowing for the introduction of nitrogen functionalities via ene-type reactions or Diels-Alder cycloadditions. In this study, we highlight the potential of horseradish peroxidase as biological mediator for the generation of reactive nitroso species under environmentally benign conditions. Exploiting a non-natural peroxidase reactivity, in combination with glucose oxidase as oxygen-activating biocatalyst, aerobic activation of a broad range of N-hydroxycarbamates and hydroxamic acids is achieved. Thus both intra- and intermolecular nitroso-ene as well as nitroso-Diels-Alder reactions are performed with high efficiency. Relying on a commercial and robust enzyme system, the aqueous catalyst solution can be recycled over numerous reaction cycles without significant loss of activity. Overall, this green and scalable C-N bond-forming strategy enables the production of allylic amides and various N-heterocyclic building blocks utilizing only air and glucose as sacrificial reagents.

Semi-circle magnetophoretic separation under rotated magnetic field for colorimetric biosensing of Salmonella

Magnetic separation was often applied to isolate and concentrate foodborne bacteria using immunomagnetic nanobeads before downstream bacterial detection. However, nanobead-bacteria conjugates (magnetic bacteria) were coexisting with excessive unbound nanobeads, limiting these nanobeads on magnetic bacteria to further act as signal probes for bacterial detection. Here, a new microfluidic magnetophoretic biosensor was elaboratively developed using a rotated high gradient magnetic field and platinum modified immunomagnetic nanobeads for continuous-flow isolation of magnetic bacteria from free nanobeads, and combined with nanozyme signal amplification for colorimetric biosensing of Salmonella. First, the platinum modified immunomagnetic nanobeads were mixed with the bacterial sample to form the magnetic bacteria, and magnetically separated to eliminate non-magnetic background. Then, the mixture of free immunomagnetic nanobeads and magnetic bacteria was injected with sheath flow (PBS) at higher flowrate into the semi-circle magnetophoretic separation channel under rotated magnetic field, which was generated by two repulsive cylindric magnets and their in-between ring iron gear, leading to continuous-flow isolation of magnetic bacteria from free immunomagnetic nanobeads because they suffered from different magnetic forces and thus had different deviating positions at the outlet. Finally, the separated magnetic bacteria and unbound magnetic nanobeads were respectively collected and used to catalyze coreless substrate into blue product, which was further analyzed using the microplate reader to obtain bacterial amount. This biosensor could determinate Salmonella as low as 41 CFU/mL in 40 min.

Protection of catalytic cofactors by polypeptides as a driver for the emergence of primordial enzymes

Enzymes catalyze the chemical reactions of life. For nearly half of known enzymes, catalysis requires the binding of small molecules known as cofactors. Polypeptide-cofactor complexes likely formed at a primordial stage and became starting points for the evolution of many efficient enzymes. Yet, evolution has no foresight so the driver for the primordial complex formation is unknown. Here, we use a resurrected ancestral TIM-barrel protein to identify one potential driver. Heme binding at a flexible region of the ancestral structure yields a peroxidation catalyst with enhanced efficiency when compared to free heme. This enhancement, however, does not arise from protein-mediated promotion of catalysis. Rather, it reflects protection of bound heme from common degradation processes and a resulting longer life time and higher effective concentration for the catalyst. Protection of catalytic cofactors by polypeptides emerges as a general mechanism to enhance catalysis and may have plausibly benefited primordial polypeptide-cofactor associations.

Comparative studies of soluble and immobilized Fe(III) heme-peptide complexes as alternative heterogeneous biocatalysts

Fe(III) heme is known to possess low catalytic activity when exposed to hydrogen peroxide and a reducing substrate. Efficient non-covalently linked Fe(III) heme-peptide complexes may represent suitable alternatives as a new group of green catalysts. Here, we evaluated a set of heme-peptide complexes by determination of their peroxidase-like activity and the kinetics of the catalytic conversion in both, the soluble and the immobilized state. We show the impact of peptide length on binding of the peptides to Fe(III) heme and the catalytic activity. Immobilization of the peptide onto a polymer support maintains the catalytic performance of the Fe(III) heme-peptide complex. This study thus opens up a new perspective with regard to the development of heterogeneous biocatalysts with a peroxidase-like activity.

Biological oxidation methods for the removal of organic and inorganic contaminants from wastewater: A comprehensive review

Enzyme-based bioremediation is a simple, cost-effective, and environmentally friendly method for isolating and removing a wide range of environmental pollutants. This study is a comprehensive review of recent studies on the oxidation of pollutants by biological oxidation methods, performed individually or in combination with other methods. The main bio-oxidants capable of removing all types of pollutants, such as organic and inorganic molecules, from fungi, bacteria, algae, and plants, and different types of enzymes, as well as the removal mechanisms, were investigated. The use of mediators and modification methods to improve the performance of microorganisms and their resistance under harsh real wastewater conditions was discussed, and numerous case studies were presented and compared. The advantages and disadvantages of conventional and novel immobilization methods, and the development of enzyme engineering to adjust the content and properties of the desired enzymes, were also explained. The optimal operating parameters such as temperature and pH, which usually lead to the best performance, were presented. A detailed overview of the different combination processes was also given, including bio-oxidation in coincident or consecutive combination with adsorption, advanced oxidation processes, and membrane separation. One of the most important issues that this study has addressed is the removal of both organic and inorganic contaminants, taking into account the actual wastewaters and the economic aspect.

Designed High-Redox Potential Laccases Exhibit High Functional Diversity

White-rot fungi secrete an impressive repertoire of high-redox potential laccases (HRPLs) and peroxidases for efficient oxidation and utilization of lignin. Laccases are attractive enzymes for the chemical industry due to their broad substrate range and low environmental impact. Since expression of functional recombinant HRPLs is challenging, however, iterative-directed evolution protocols have been applied to improve their expression, activity, and stability. We implement a rational, stabilize-and-diversify strategy to two HRPLs that we could not functionally express. First, we use the PROSS stability-design algorithm to allow functional expression in yeast. Second, we use the stabilized enzymes as starting points for FuncLib active-site design to improve their activity and substrate diversity. Four of the FuncLib-designed HRPLs and their PROSS progenitor exhibit substantial diversity in reactivity profiles against high-redox potential substrates, including lignin monomers. Combinations of 3–4 subtle mutations that change the polarity, solvation, and sterics of the substrate-oxidation site result in orders of magnitude changes in reactivity profiles. These stable and versatile HRPLs are a step toward generating an effective lignin-degrading consortium of enzymes that can be secreted from yeast. The stabilize-and-diversify strategy can be applied to other challenging enzyme families to study and expand the utility of natural enzymes.

Towards Solving the PFAS Problem: The Potential Role of Metal-Organic Frameworks

Per- and polyfluoroalkyl substances (PFAS) are a group of recalcitrant molecules that have been used since the 1940s in a variety of applications. They are now linked to a host of negative health outcomes and are extremely resistant to degradation under environmental conditions. Currently, membrane technologies or adsorbents are used to remediate contaminated water. These techniques are either inefficient at capturing smaller PFAS molecules, have high energy demands, or result in concentrated waste that must be incinerated at high temperatures. This Review focuses on what role metal-organic frameworks (MOFs) may play in addressing the PFAS problem. Specifically, how the unique properties of MOFs such as their well-defined pore sizes, ultra-high internal surface area, and tunable surface chemistry may be a sustainable solution for PFAS contamination.

Copper metal organic framework as natural oxidase mimic for effective killing of Gram-negative and Gram-positive bacteria

Nanozymes have been widely studied as substitutes for natural enzymes. However, the delicacy of their structures and their unclear catalytic sites make it difficult to maintain their structural robustness and catalytic durability. By mimicking active catalytic sites of natural enzymes and combining them with distinct channels of metal organic frameworks (MOFs), an active copper mimetic oxidase enzyme (Cu-MOF) was designed and synthesized with good structure and clear catalytic sites for improvement in catalytic activity. The Cu-MOFs showed excellent oxidase-like activity with a low K_m of 1.09 mM and exogenous ROS generation capacity. The Cu-MOFs exhibited antibacterial efficacy at a low concentration of 12.5 μg mL^-1 by an oxidative stress response. These Cu-MOFs with their simple design and effective oxidase mimicking show attractive application prospects in the field of antibacterial and enzyme catalysis.

Encapsulation of peroxidase on hydrogel sodium polyacrylate spheres incorporated by silver and gold nanoparticles: A comparative study

The selectivity of biocatalysts based on enzymes, eco-friendly reaction systems, and strong catalyst performance is exceptionally compelling. For improving enzyme recyclability and stability, a good option that has been proved is immobilization. For enzyme immobilization, hydrogel sodium polyacrylate combined with nanoparticles is an interesting class of support matrices as compared to others. This study synthesizes and uses the cross-linked hydrogel sodium polyacrylate-decorated gold or silver nanoparticles (HSP/AuNPs or AgNPs) as immobilized support for peroxidase and FTIR characterizes it. The novel supports immobilized system properties enhanced biocompatibility. They have attained a greater immobilization yield (91% with HSP/AuNPs and 84% with HSP/AgNPs). The rest of the immobilized peroxidase activity, after 10 recurring cycles of HSP/AuNPs was 61% and HSP/AgNPs was 54% . The remaining activity of the immobilized enzyme onto HSP/AgNPs, after storing at 4°C for 6 weeks, was 73% and HSP/AuNPs was 75% of its initial activity. It was revealed that the optimum temperature for the free enzyme and the immobilized enzyme was 50°C and 50–60°C, respectively. For the immobilized enzyme, the optimum pH is 7–7.5, as compared to the optimum pH of free enzyme pH 6.5.

Stable and Functionally Diverse Versatile Peroxidases Designed Directly from Sequences

White-rot fungi secrete a repertoire of high-redox potential oxidoreductases to efficiently decompose lignin. Of these enzymes, versatile peroxidases (VPs) are the most promiscuous biocatalysts. VPs are attractive enzymes for research and industrial use but their recombinant production is extremely challenging. To date, only a single VP has been structurally characterized and optimized for recombinant functional expression, stability, and activity. Computational enzyme optimization methods can be applied to many enzymes in parallel but they require accurate structures. Here, we demonstrate that model structures computed by deep-learning-based ab initio structure prediction methods are reliable starting points for one-shot PROSS stability-design calculations. Four designed VPs encoding as many as 43 mutations relative to the wildtype enzymes are functionally expressed in yeast, whereas their wildtype parents are not. Three of these designs exhibit substantial and useful diversity in their reactivity profiles and tolerance to environmental conditions. The reliability of the new generation of structure predictors and design methods increases the scale and scope of computational enzyme optimization, enabling efficient discovery and exploitation of the functional diversity in natural enzyme families directly from genomic databases.

Bundling the removal of emerging contaminants with the production of ligninolytic enzymes from residual streams

Abstract

Enzymes offer interesting features as biological catalysts for industry: high specificity, activity under mild conditions, accessibility, and environmental friendliness. Being able to produce enzymes in large quantities and having them available in a stable and reusable form reduces the production costs of any enzyme-based process. Agricultural residues have recently demonstrated their potential as substrates to produce ligninolytic enzymes by different white rot fungi. In this study, the biotechnological production of a manganese peroxidase (MnP) by Irpex lacteus was conducted through solid-state fermentation (SSF) with wheat straw as substrate and submerged fermentation (SmF) employing wheat straw extract (WSE). The obtained enzyme cocktail also showed manganese-independent activity (MiP), related to the presence of a short MnP and a dye-decolorizing peroxidase (DyP) which was confirmed by shotgun proteomic analyses. In view of the enhanced production of ligninolytic enzymes in SmF, different parameters such as WSE concentration and nitrogen source were evaluated. The highest enzyme titers were obtained with a medium formulated with glucose and peptone (339 U/L MnP and 15 U/L MiP). The scale-up to a 30 L reactor achieved similar activities, demonstrating the feasibility of enzyme production from the residual substrate at different production scales. Degradation of five emerging pollutants was performed to demonstrate the high oxidative capacity of the enzyme. Complete removal of hormones and bisphenol A was achieved in less than 1 h, whereas almost 30% degradation of carbamazepine was achieved in 24 h, which is a significant improvement compared to previous enzymatic treatments of this compound.

Key points

• Wheat straw extract is suitable for the growth of I. lacteus.

• The enzyme cocktail obtained allows the degradation of emerging contaminants.

• Mn-dependent and Mn-independent activities increases the catalytic potential.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-022-11776-7.

Identification of Fe(iii)–OH species as a catalytic intermediate in plant peroxidases at high H2O2 concentration

The structure for compound III formed after exposure of plant heme peroxidases to excess H2O2 seems to be a hydroxylated form, providing new evidence for understanding the structural basis of the substrate-induced suicidal behavior of these enzymes.

Characterization of Two Hydrogen Peroxide Resistant Peroxidases from Rhodococcus opacus 1CP

The dye-decolorizing peroxidases (DyP) are a family of heme-dependent enzymes present on a broad spectrum of microorganisms. While the natural function of these enzymes is not fully understood, their capacity to degrade highly contaminant pigments such as azo dyes or anthraquinones make them excellent candidates for applications in bioremediation and organic synthesis. In this work, two novel DyP peroxidases from the organism Rhodococcus opacus 1CP (DypA and DypB) were cloned and expressed in Escherichia coli. The enzymes were purified and biochemically characterized. The activities of the two DyPs via 2,2′-azino-bis [3-ethylbenzthiazoline-6-sulphonic acid] (ABTS) assay and against Reactive Blue 5 were assessed and optimized. Results showed varying trends for DypA and DypB. Remarkably, these enzymes presented a particularly high tolerance towards H2O2, retaining its activities at about 10 mM H2O2 for DypA and about 4.9 mM H2O2 for DypB.

Ether Oxidation by an Evolved Fungal Heme-Peroxygenase: Insights into Substrate Recognition and Reactivity

Ethers can be found in the environment as structural, active or even pollutant molecules, although their degradation is not efficient under environmental conditions. Fungal unspecific heme-peroxygenases (UPO were reported to degrade low-molecular-weight ethers through an H₂O₂-dependent oxidative cleavage mechanism. Here, we report the oxidation of a series of structurally related aromatic ethers, catalyzed by a laboratory-evolved UPO (PaDa-I) aimed at elucidating the factors influencing this unusual biochemical reaction. Although some of the studied ethers were substrates of the enzyme, they were not efficiently transformed and, as a consequence, secondary reactions (such as the dismutation of H₂O₂ through catalase-like activity and suicide enzyme inactivation) became significant, affecting the oxidation efficiency. The set of reactions that compete during UPO-catalyzed ether oxidation were identified and quantified, in order to find favorable conditions that promote ether oxidation over the secondary reactions.

Photocatalyst-enzyme hybrid systems for light-driven biotransformation

Enzymes catalyse target reactions under mild conditions with high efficiency, as well as excellent regional-, stereo-, and enantiomeric selectivity. Photocatalysis utilises sustainable and environment-friendly light power to realise efficient chemical conversion. By combining the interdisciplinary advantages of photo- and enzymatic catalysis, the photocatalyst-enzyme hybrid systems have proceeded various light-driven biotransformation with high efficiency under environmentally benign conditions, thus, attracting unparalleled focus during the last decades. It has also been regarded as a promising pathway towards green chemistry utilising ubiquitous solar energy. This systematic review gives insight into this research field by classifying the existing photocatalyst-enzyme hybrid systems into three sections based on different hybridizing modes between photo- and enzymatic catalysis. Furthermore, existing challenges and proposed strategies are discussed within this context. The first system summarised is the cofactor-mediated hybrid system, in which natural/artificial cofactors act as reducing equivalents that connect photocatalysts with enzymes for light-driven enzymatic biotransformation. Second, the direct contact-based photocatalyst-enzyme hybrid systems are described, including two different kinds of electron exchange sites on the enzyme molecules. Third, some cases where photocatalysts and enzymes are integrated into a reaction cascade with specific intermediates will be discussed in the following chapter. Finally, we provide perspective concerning the future of this field.

Simultaneous degradation of two mycotoxins enabled by a fusion enzyme in food-grade recombinant Kluyveromyces lactis

Aflatoxin B1 (AFB1) and zearalenone (ZEN) are two predominant mycotoxins ubiquitously found in corn, peanuts, and other grains, which pose a great threat to human health. Therefore, safe and effective methods for detoxification of these mycotoxins are urgently needed. To achieve simultaneous degradation of multiple mycotoxins, a fusion enzyme ZPF1 was constructed by linking zearalenone hydrolase and manganese peroxidase with a linker peptide GGGGS. This fusion enzyme was secretory expressed successfully in the newly constructed food-grade recombinant strain Kluyveromyces lactis GG799(pKLAC1-ZPF1), and was investigated with the mycotoxins degradation efficiency in two reaction systems. Results showed that both AFB1 and ZEN can be degraded by ZPF1 in reaction system 1 (70.0 mmol/L malonic buffer with 1.0 mmol/L MnSO4, 0.1 mmol/L H2O2, 5.0 µg/mL AFB1 and ZEN, respectively) with the ratios of 46.46% and 38.76%, respectively. In reaction system 2 (50.0 mmol/L Tris-HCl, with 5.0 µg/mL AFB1 and ZEN, respectively), AFB1 cannot be degraded while ZEN can be degraded with the ratio of 35.38%. To improve the degradation efficiency of these mycotoxins, optimization of the induction and degradation conditions were fulfilled subsequently. The degradation ratios of AFB1 and ZEN by ZPF1 in reaction system 1 reached 64.11% ± 2.93% and 46.21% ± 3.17%, respectively. While in reaction system 2, ZEN was degraded by ZPF1 at a ratio of 41.45% ± 3.34%. The increases of degradation ratios for AFB1 and ZEN in reaction system 1 were 17.65% and 7.45%, respectively, while that for ZEN in reaction system 2 was 6.07%, compared with the unoptimized results.

Identification and Expression of New Unspecific Peroxygenases - Recent Advances, Challenges and Opportunities

In 2004, the fungal heme-thiolate enzyme subfamily of unspecific peroxygenases (UPOs) was first described in the basidiomycete Agrocybe aegerita. As UPOs naturally catalyze a broad range of oxidative transformations by using hydrogen peroxide as electron acceptor and thus possess a great application potential, they have been extensively studied in recent years. However, despite their versatility to catalyze challenging selective oxyfunctionalizations, the availability of UPOs for potential biotechnological applications is restricted. Particularly limiting are the identification of novel natural biocatalysts, their production, and the description of their properties. It is hence of great interest to further characterize the enzyme subfamily as well as to identify promising new candidates. Therefore, this review provides an overview of the state of the art in identification, expression, and screening approaches of fungal UPOs, challenges associated with current protein production and screening strategies, as well as potential solutions and opportunities.

Elimination of selected heterocyclic aromatic emerging contaminants from water using soybean peroxidase

Widespread occurrence of various heterocyclic aromatic compounds is reported in concentrations from 1 to 20 μg/L in surface and groundwater as well as influents and effluents of wastewater treatment plants around the world. These so-called emerging contaminants and their metabolites can cause adverse effects on the environment and humans, even at very low concentration, hence raised environmental concerns. In this study, feasibility of soybean peroxidase-catalyzed removal of three selected heterocyclic aromatics from water was investigated, including sensitivity to the most important operational conditions, pH (range 3.6-9.0), H2O2 concentration (range 0.10-1.50 mM), and enzyme activity (range 0.001-5.0 U/mL). 3-Hydroxycoumarin and 2-aminobenzoxaozle were found to be substrates for the enzyme, having ≥95% and 45% removal efficiency with most effective pHs of 7.0 and 6.0, respectively. Time course study was also conducted to determine the initial first-order rate constants and half-lives; half-lives normalized for enzyme activity (0.0257 and 452 min for the respective substrates) are compared with those of 21 other compounds reactive with soybean peroxidase. High-resolution mass spectrometry was employed to characterize the plausible oligomerization products of enzymatic treatment, which revealed formation of dimers and trimers of the two substrates.

Biocatalytic remediation of industrial pollutants for environmental sustainability: Research needs and opportunities

An increasing quantum of pollutants from various industrial sector activities represents a severe menace to environmental & ecological balance. Bioremediation is gaining flow globally due to its cost-effective and environment-friendly nature. Understanding biodegradation mechanisms is of high ecological significance. Application of microbial enzymes has been reported as sustainable approach to mitigate the pollution. Immobilized enzyme catalyzed transformations are getting accelerated attention as potential alternatives to physical and chemical methods. The attention is now also focused on developing novel protein engineering strategies and bioreactor design systems to ameliorate overall biocatalysis and waste treatment further. This paper presents and discusses the most advanced and state of the art scientific & technical developments about biocatalytic remediation of industrial pollutants. It also covers various biocatalysts and the associated sustainable technologies to remediate various pollutants from waste streams. Enzyme production and immobilization in bioreactors have also been discussed. This paper also covers challenges and future research directions in this field.

Mechanism of action, sources, and application of peroxidases

Peroxidase is an enzyme in the group of oxidoreductases that is widely distributed in nature. It can catalyze the oxidation of various organic and inorganic substrates by reacting with hydrogen peroxide and similar molecules. Due to its wide catalytic activity, peroxidases can act in the removal of both phenolic compounds and peroxides, in chemical synthesis and, according to recent studies, in mycotoxin degradation. Therefore, this study aimed at introducing an overview of the mechanism of peroxidase action, extraction sources, mycotoxin degradation capacity and other potential applications in the food industry.

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.

Exploring the Diversity of Fungal DyPs in Mangrove Soils to Produce and Characterize Novel Biocatalysts

The functional diversity of the New Caledonian mangrove sediments was examined, observing the distribution of fungal dye-decolorizing peroxidases (DyPs), together with the complete biochemical characterization of the main DyP. Using a functional metabarcoding approach, the diversity of expressed genes encoding fungal DyPs was investigated in surface and deeper sediments, collected beneath either Avicennia marina or Rhizophora stylosa trees, during either the wet or the dry seasons. The highest DyP diversity was observed in surface sediments beneath the R. stylosa area during the wet season, and one particular operational functional unit (OFU1) was detected as the most abundant DyP isoform. This OFU was found in all sediment samples, representing 51–100% of the total DyP-encoding sequences in 70% of the samples. The complete cDNA sequence corresponding to this abundant DyP (OFU 1) was retrieved by gene capture, cloned, and heterologously expressed in Pichia pastoris. The recombinant enzyme, called DyP1, was purified and characterized, leading to the description of its physical–chemical properties, its ability to oxidize diverse phenolic substrates, and its potential to decolorize textile dyes; DyP1 was more active at low pH, though moderately stable over a wide pH range. The enzyme was very stable at temperatures up to 50 °C, retaining 60% activity after 180 min incubation. Its ability to decolorize industrial dyes was also tested on Reactive Blue 19, Acid Black, Disperse Blue 79, and Reactive Black 5. The effect of hydrogen peroxide and sea salt on DyP1 activity was studied and compared to what is reported for previously characterized enzymes from terrestrial and marine-derived fungi.

Bioinspired Cooperative Photobiocatalytic Regeneration of Oxidized Nicotinamide Cofactors for Catalytic Oxidations

Inspired by water-forming NAD(P)H oxidases, a cooperative photobiocatalytic system has been designed to aerobically regenerate the oxidized nicotinamide cofactors. Photocatalysts enable NAD(P)H oxidation with O₂ under visible-light irradiation, producing H₂ O₂ as a byproduct, which is subsequently used as an oxidant by the horseradish peroxidase mediator system (PMS) to oxidize NAD(P)H. The photobiocatalytic system shows a turnover frequency of 8800 min^-1 in the oxidation of NAD(P)H. Photobiocatalytic NAD(P)H oxidation proceeds smoothly at pH 6-9. In addition to natural NAD(P)H, synthetic biomimetics are also good substrates for this regeneration system. Total turnover numbers of up to 180000 are obtained for the cofactor when the photobiocatalytic regeneration system is coupled with dehydrogenase-catalyzed oxidations. It may be a promising protocol to recycle the oxidized cofactors for catalytic oxidations.

Early modification of cytochrome c by hydrogen peroxide triggers its fast degradation

Cytochrome c (cyt c), in addition to its function as an electron shuttle in respiratory chain, is able to perform as a pseudo-peroxidase with a critical role during apoptosis. Incubation of cyt c with an excess of hydrogen peroxide leads to a suicide inactivation of the protein, which is accompanied by heme destruction and covalent modification of numerous amino acid residues. Although steady-state reactions of cyt c with an excess of hydrogen peroxide represent non-physiological conditions, they might be used for analysis of the first-modified amino acid in in vivo. Here, we observed oxidation of tyrosine residues 67 and 74 and heme as the first modifications found upon incubation with hydrogen peroxide. The positions of the oxidized tyrosines suggest a possible migration pathway of hydrogen peroxide-induced radicals from the site of heme localization to the protein surface. Analysis of a size of folded fraction of cyt c upon limited incubation with hydrogen peroxide indicates that the early oxidation of amino acids triggers an accelerated destruction of cyt c. Position of channels from molecular dynamics simulation structures of cyt c points to a location of amino acid residues exposed to reactive oxidants that are thus more prone to covalent modification.

Enzyme Cascade Reaction Involving Lytic Polysaccharide Monooxygenase and Dye-Decolorizing Peroxidase for Chitosan Functionalization

In situ H₂O₂ generation systems are efficient for H₂O₂-dependent biocatalytic oxidation reactions. Here, we report that lytic polysaccharide monooxygenases (LPMOs), copper-dependent polysaccharide monooxygenases, can efficiently supply H₂O₂ in situ to dye-decolorizing peroxidases (DyPs) using substrate gallic acid (GA) for chitosan functionalization. The maximum grafting ratio induced by the cascade reaction was significantly higher than that achieved by a reaction with initial exogenous H₂O₂. The maximum grafting ratio was obtained with 12 g/L GA, 5.6 mg/L DyP, 20-30 mg/L LPMO, and pH 4.5-5.0. UV-vis, Fourier transform infrared (FT-IR), and nuclear magnetic resonance (¹H NMR) spectroscopy confirmed GA grafting onto chitosan. X-ray diffraction (XRD) analysis and thermogravimetric analysis (TGA) indicated that GA-chitosan conjugates had lower thermal stability and crystallinity than chitosan. The GA-chitosan conjugates had significantly higher antioxidant activity than chitosan. This study supplies a green and high-efficiency approach to achieve an enzymatic cascade reaction for chitosan functionalization and has potential applications in H₂O₂-dependent biocatalytic oxidation reactions.

Cascade Biocatalysis Designed for the Allylic Oxidation of α-Pinene

A biocatalytic cascade system using a cocktail of oxidoreductase enzymes (2-1B peroxidase and M120 laccase) was designed for the allylic oxidation of (+)-α-pinene into value-added products (e.g., verbenol and verbenone). The oxidative transformation involved a two-step process as follows: (+)-α-pinene was (i) oxidized on the allylic position with H2O2 mainly assisted by 2-1B peroxidase leading to verbenol as the principal reaction product, and (ii) directed to verbenone in the presence of M120 laccase responsible for further oxidation of verbenol to verbenone. The reaction environment was ensured by the acetate buffer (0.1 M, pH = 5). Optimum values for the experimental parameters (e.g., concentration of 2-1B peroxidase, M120 laccase, and H2O2) were set up. The biocatalytic cascade process was monitored for 24 h in order to evaluate the process pathway. Maximum performance under optimum conditions was reached after 5 h incubation time (e.g., 80% (+)-α-pinene conversion and 70% yield in verbenol). Therefore, the developed biocatalytic cascade system offered promising perspectives for (+)-α-pinene valorization.

Structural and Biosynthetic Analysis of the Fabrubactins, Unusual Siderophores from Agrobacterium fabrum Strain C58

Siderophores are iron-chelating molecules produced by microorganisms and plants to acquire exogenous iron. Siderophore biosynthetic enzymology often produces elaborate and unique molecules through unusual reactions to enable specific recognition by the producing organisms. Herein, we report the structure of two siderophore analogs from Agrobacterium fabrum strain C58, which we named fabrubactin (FBN) A and FBN B. Additionally, we characterized the substrate specificities of the NRPS and PKS components. The structures suggest unique Favorskii-like rearrangements of the molecular backbone that we propose are catalyzed by the flavin-dependent monooxygenase, FbnE. FBN A and B contain a 1,1-dimethyl-3-amino-1,2,3,4-tetrahydro-7,8-dihydroxy-quinolin (Dmaq) moiety previously seen only in the anachelin cyanobacterial siderophores. We provide evidence that Dmaq is derived from l-DOPA and propose a mechanism for the formation of the mature Dmaq moiety. Our bioinformatic analyses suggest that FBN A and B and the anachelins belong to a large and diverse siderophore family widespread throughout the Rhizobium/Agrobacterium group, α-proteobacteria, and cyanobacteria.

Non-invasive detection of glucose in human urine using a color-generating copper NanoZyme

Renal complications are long-term effect of diabetes mellitus where glucose is excreted in urine. Therefore, reliable glucose detection in urine is critical. While commercial urine strips offer a simple way to detect urine sugar, poor sensitivity and low reliability limit their use. A hybrid glucose oxidase (GOx)/horseradish peroxidase (HRP) assay remains the gold standard for pathological detection of glucose. A key restriction is poor stability of HRP and its suicidal inactivation by hydrogen peroxide, a key intermediate of the GOx-driven reaction. An alternative is to replace HRP with a robust inorganic enzyme-mimic or NanoZyme. While colloidal NanoZymes show promise in glucose sensing, they detect low concentrations of glucose, while urine has high (mM) glucose concentration. In this study, a free-standing copper NanoZyme is used for the colorimetric detection of glucose in human urine. The sensor could operate in a biologically relevant dynamic linear range of 0.5-15 mM, while showing minimal sample matrix effect such that glucose could be detected in urine without significant sample processing or dilution. This ability could be attributed to the Cu NanoZyme that for the first time showed an ability to promote the oxidation of a TMB substrate to its double oxidation diimine product rather than the charge-transfer complex product commonly observed. Additionally, the sensor could operate at a single pH without the need to use different pH conditions as used during the gold standard assay. These outcomes outline the high robustness of the NanoZyme sensing system for direct detection of glucose in human urine. Graphical abstract.

Hematin-conjugated gelatin as an effective catalyst for preparing biological hydrogels

The design of Ge–He provides feasible strategies for mimicking HRP enzyme to fabricate biomedical hydrogels.

Nuclear Waste and Biocatalysis: A Sustainable Liaison?

It is well-known that energy-rich radiation induces water splitting, eventually yielding hydrogen peroxide. Synthetic applications, however, are scarce and to the best of our knowledge, the combination of radioactivity with enzyme-catalysis has not been considered yet. Peroxygenases utilize H₂O₂ as an oxidant to promote highly selective oxyfunctionalization reactions but are also irreversibly inactivated in the presence of too high H₂O₂ concentrations. Therefore, there is a need for efficient in situ H₂O₂ generation methods. Here, we show that radiolytic water splitting can be used to promote specific biocatalytic oxyfunctionalization reactions. Parameters influencing the efficiency of the reaction and current limitations are shown. Particularly, oxidative inactivation of the biocatalyst by hydroxyl radicals influences the robustness of the overall reaction. Radical scavengers can alleviate this issue, but eventually, physical separation of the enzymes from the ionizing radiation will be necessary to achieve robust reaction schemes. We demonstrate that nuclear waste can also be used to drive selective, peroxygenase-catalyzed oxyfunctionalization reactions, challenging our view on nuclear waste in terms of sustainability.

Production and characterisation of a novel actinobacterial DyP-type peroxidase and its application in coupling of phenolic monomers

The extracellular peroxidase from Streptomyces albidoflavus BSII#1 was purified to near homogeneity using sequential steps of acid and acetone precipitation, followed by ultrafiltration. The purified peroxidase was characterised and tested for the ability to catalyse coupling reactions between selected phenolic monomer pairs. A 46-fold purification of the peroxidase was achieved, and it was shown to be a 46 kDa haem peroxidase. Unlike other actinobacteria-derived peroxidases, it was only inhibited (27 % inhibition) by relatively high concentrations of sodium azide (5 mM) and was capable of oxidising eleven (2,4-dichlorophenol, 2,6-dimethoxyphenol, 4-tert-butylcatechol, ABTS, caffeic acid, catechol, guaiacol, l-DOPA, o-aminophenol, phenol, pyrogallol) of the seventeen substrates tested. The peroxidase remained stable at temperatures of up to 80 °C for 60 min and retained >50 % activity after 24 h between pH 5.0-9.0, but was most sensitive to incubation with hydrogen peroxide (H₂O₂; 0.01 mM), l-cysteine (0.02 mM) and ascorbate (0.05 mM) for one hour. It was significantly inhibited by all organic solvents tested (p ≤ 0.05). The K_m and V_max values of the partially purified peroxidase with the substrate 2,4-DCP were 0.95 mM and 0.12 mmol min^-1, respectively. The dyes reactive blue 4, reactive black 5, and Azure B, were all decolourised to a certain extent: approximately 30 % decolourisation was observed after 24 h (1 μM dye). The peroxidase successfully catalysed coupling reactions between several phenolic monomer pairs including catechin-caffeic acid, catechin-catechol, catechin-guaiacol and guaiacol-syringaldazine under the non-optimised conditions used in this study. Genome sequencing confirmed the identity of strain BSII#1 as a S. albidoflavus strain. In addition, the genome sequence revealed the presence of one peroxidase gene that includes the twin arginine translocation signal sequence of extracellular proteins. Functional studies confirmed that the peroxidase produced by S. albidoflavus BSII#1 is part of the dye-decolourising peroxidase (DyP-type) family.

Exploring the Role of Phenylalanine Residues in Modulating the Flexibility and Topography of the Active Site in the Peroxygenase Variant PaDa-I

Unspecific peroxygenases (UPOs) are fungal heme-thiolate enzymes able to catalyze a wide range of oxidation reactions, such as peroxidase-like, catalase-like, haloperoxidase-like, and, most interestingly, cytochrome P450-like. One of the most outstanding properties of these enzymes is the ability to catalyze the oxidation a wide range of organic substrates (both aromatic and aliphatic) through cytochrome P450-like reactions (the so-called peroxygenase activity), which involves the insertion of an oxygen atom from hydrogen peroxide. To catalyze this reaction, the substrate must access a channel connecting the bulk solution to the heme group. The composition, shape, and flexibility of this channel surely modulate the catalytic ability of the enzymes in this family. In order to gain an understanding of the role of the residues comprising the channel, mutants derived from PaDa-I, a laboratory-evolved UPO variant from Agrocybe aegerita, were obtained. The two phenylalanine residues at the surface of the channel, which regulate the traffic towards the heme active site, were mutated by less bulky residues (alanine and leucine). The mutants were experimentally characterized, and computational studies (i.e., molecular dynamics (MD)) were performed. The results suggest that these residues are necessary to reduce the flexibility of the region and maintain the topography of the channel.

Antioxidant Activity of Synthetic Polymers of Phenolic Compounds

In recent years, developing potent antioxidants has been a very active area of research. In this context, phenolic compounds have been evaluated for their antioxidant activity. However, the use of phenolic compounds has also been limited by poor antioxidant activity in several in vivo studies. Polymeric phenols have received much attention owing to their potent antioxidant properties and increased stability in aqueous systems. To be truly effective in biological applications, it is important that these polymers be synthesized using benign methods. In this context, enzyme catalyzed synthesis of polymeric phenols has been explored as an environmentally friendly and safer approach. This review summarizes work in enzymatic syntheses of polymers of phenols. Several assays have been developed to determine the antioxidant potency of these polymeric phenols. These assays are discussed in detail along with structure-property relationships. A deeper understanding of factors affecting antioxidant activity would provide an opportunity for the design of versatile, high performing polymers with enhanced antioxidant activity.

Plasma-Driven in Situ Production of Hydrogen Peroxide for Biocatalysis

Peroxidases and peroxygenases are promising classes of enzymes for biocatalysis because of their ability to carry out one-electron oxidation reactions and stereoselective oxyfunctionalizations. However, industrial application is limited, as the major drawback is the sensitivity toward the required peroxide substrates. Herein, we report a novel biocatalysis approach to circumvent this shortcoming: in situ production of H2 O2 by dielectric barrier discharge plasma. The discharge plasma can be controlled to produce hydrogen peroxide at desired rates, yielding desired concentrations. Using horseradish peroxidase, it is demonstrated that hydrogen peroxide produced by plasma treatment can drive the enzymatic oxidation of model substrates. Fungal peroxygenase is then employed to convert ethylbenzene to (R)-1-phenylethanol with an ee of >96 % using plasma-generated hydrogen peroxide. As direct treatment of the reaction solution with plasma results in reduced enzyme activity, the use of plasma-treated liquid and protection strategies are investigated to increase total turnover. Technical plasmas present a noninvasive means to drive peroxide-based biotransformations.

Laccases and peroxidases: The smart, greener and futuristic biocatalytic tools to mitigate recalcitrant emerging pollutants

Various organic pollutants so-called emerging pollutants (EPs), including active residues from pharmaceuticals, pesticides, surfactants, hormones, and personal care products, are increasingly being detected in numerous environmental matrices including water. The persistence of these EPs can cause adverse ecological and human health effects even at very small concentrations in the range of micrograms per liter or lower, hence called micropollutants (MPs). The existence of EPs/MPs tends to be challenging to mitigate from the environment effectively. Unfortunately, most of them are not removed during the present-day treatment plants. So far, a range of treatment processes and degradation methods have been introduced and deployed against various EPs and/or MPs, such as ultrafiltration, nanofiltration, advanced oxidation processes (AOPs) and enzyme-based treatments coupled with membrane filtrations. To further strengthen the treatment processes and to overcome the EPs/MPs effective removal dilemma, numerous studies have revealed the applicability and notable biocatalytic potentialities of laccases and peroxidases to degrade different classes of organic pollutants. Exquisite selectivity and unique catalytic properties make these enzymes powerful biocatalytic candidates for bio-transforming an array of toxic contaminants to harmless entities. This review focuses on the use of laccases and peroxidases, such as soybean peroxidase (SBP), horseradish peroxidase (HRP), lignin peroxidase (LiP), manganese peroxidase (MnP), and chloroperoxidase (CPO) as a greener oxidation route towards efficient and effective removal or degradation of EPs/MPs.