Electron transfer and reaction mechanism of laccases

Engineering of Bacillus Laccase frL103 for Highly Efficient Degradation of Aflatoxin B1

Aflatoxin B1 (AFB1) is a highly toxic mycotoxin that poses significant risks to food safety and public health. Bacillus laccases have shown potential for degrading AFB1, but their catalytic efficiency remains suboptimal. This study explores the structure-function relationship of Bacillus vallismortis laccase frL103 by employing molecular modeling, site-directed mutagenesis, and molecular dynamics (MD) simulations. Eight key amino acid residues in the substrate binding pocket of frL103 were selected for alanine mutagenesis. After the enzymatic properties were evaluated, site 418, a loop region near the T1 copper, was subjected to saturation mutagenesis. Site saturation mutation at T418 identified the T418A and T418S as exhibiting the highest AFB1 degradation rate, with values of 56.7 and 53.6%, 1.24 and 1.17 times higher than WT (45.7%), respectively. MD simulations showed that these mutations did not significantly affect the overall structural stability of the enzyme but changed the flexibility and hydrogen bond interactions of the loop in which they were located, thereby helping to improve substrate binding and degradation. This study provides valuable insights into the structural mechanisms underlying the enhanced degradation of AFB1 and offers a basis for designing more efficient laccase mutants for bioremediation applications.

Comparative analysis of Polyethylene-Degrading Laccases: Redox Properties and Enzyme-Polyethylene Interaction Mechanism

Laccases that oxidize low-density polyethylene (LDPE) represent a promising strategy for bioremediation purposes. To rationalize or optimize their PE-oxidative activity, two fundamental factors must be considered: the enzyme's redox potential and its binding affinity/mode towards LDPE. Indeed, a stable laccase-PE complex may facilitate a thermodynamically unfavorable electron transfer, even without redox mediators. In this study, we compared the redox potential and the LDPE-binding properties of three different PE-oxidizing laccases: a fungal high-redox potential laccase from Trametes versicolor, a bacterial low-redox potential laccase from Bacillus subtilis, and the recently characterized LMCO2 from Rhodococcus opacus R7. First we found that LMCO2 is a low-potential laccase (E°=413 mV), as reported in other bacterial variants. Using computational tools, we simulated the interactions of these laccases with a large LDPE model and highlighted the key role of hydrophobic residues surrounding the T1 site. Notably, a methionine-rich loop in LMCO2 appears to enhance the formation of a stable complex with LDPE, potentially facilitating electron transfer. This study underscores the necessity for comprehensive computational strategies to analyze enzyme-polymer interactions beyond simplistic models, uncovering critical binding determinants and informing future mutagenesis experiments, in order to enhance laccase performance and rationalize variations in enzymatic activity.

Unexpected effect of an axial ligand mutation in the type 1 copper center in small laccase: structure-based analyses and engineering to increase reduction potential and activity

Type 1 copper (T1Cu) centers are crucial in biological electron transfer (ET) processes, exhibiting a wide range of reduction potentials to match their redox partners and optimize ET rates. While tuning in mononuclear T1Cu proteins like azurin has been successful, it is more difficult for multicopper oxidases. Specifically, while replacing axial methionine to leucine in azurin increased its by ∼100 mV, the corresponding M298L mutation in small laccase from Streptomyces coelicolor (SLAC) unexpectedly decreased its by 12 mV. X-ray crystallography revealed two axial water molecules in M298L-SLAC, leading to the decrease of due to decreased hydrophobicity. Structural alignment and molecular dynamics simulation indicated a key difference in T1Cu axial loop position, leading to the different outcome upon methionine to leucine mutation. Based on structural analyses, we introduced additional F195L and I200F mutations, leading to partial removal of axial waters, a 122-mV increase in , and a 7-fold increase in k cat/K M from M298L-SLAC. These findings highlight the complexity of tuning in multicopper oxidases and provide valuable insights into how structure-based protein engineering can contribute to the broader understanding of T1Cu center, and reactivity tuning for applications, such as in solar energy transfer, fuel cells, and bioremediation.

Micro-mechanism of rhamnolipid promoting acid production during anaerobic digestion: protein structures, metagenomics and molecular dynamics simulations

The addition of rhamnolipid (RL) is a promising strategy to enhance volatile fatty acids (VFAs) production in anaerobic digestion (AD) systems. However, the microscopic mechanisms underlying this enhancement remain poorly understood. This study investigates the micro-mechanisms by which RL promotes VFAs production, integrating protein structural analysis, metagenomics, and molecular dynamics simulations. Experimental results revealed that adding RL at 0.08 g/g TS significantly increased VFAs production to 11,441.8 mg COD/L. Protein structural analysis revealed disruption of amide I-related C = O groups and amide II-related CN and NH bonds, indicating the release or structural alteration of sludge proteins. Metagenomic analysis indicated an increase in the abundance of microbial communities and related genes, suggesting that RL enhanced the activity of acid-producing microorganisms and related metabolic pathways. Furthermore, molecular docking and molecular dynamics simulations indicated that RL spontaneously aggregated and absorbed acetate kinase (AK), altering its conformation and reducing structural compactness, which made acetyl phosphate (AcP) more accessible to the binding site of AK. RL reduced the energy barrier associated with the polar solvation interactions, increasing the contributions of key residues (LYS176 and GLU234) to the binding free energy, which enhanced the binding affinity of AK-AcP complex. This study provides a comprehensive molecular basis for how RL promotes VFAs production in AD, offering a promising strategy for optimizing acid production.

Deciphering the distribution and types of Multicopper oxidases in Basidiomycota fungi

Multicopper oxidases (MCOs) comprise different types of enzymes widely distributed in nature with quite diverse functions. Laccases are the most interesting MCOs from a biotechnological point of view, particularly those secreted by ligninolytic Basidiomycota fungi due to their versatility to oxidize lignin and a variety of aromatic substrates. The term "laccase" has been broadly (but sometimes erroneously) applied due to their low sequence homology and some overlapping activities with other MCO groups. We examined the distribution and phylogenetic relationships of MCOs in Basidiomycota fungi aiming to provide a complete and precise picture of the different MCO types across the division, including fungal orders phylogenetically distant from those typically studied. The phylogenetic tree revealed eight clusters of MCOs, each sharing common sequence/structural features. With this information we classified the MCOs in eight groups and described their distinctive amino acid residues. These eight MCO types are: laccases (LAC), ferroxidases (FOX), laccase-ferroxidases (LAC-FOX), ascorbate oxidases (AO), fungal pigment MCOs, and three new groups of laccase-like enzymes or "atypical laccases" related to but different from laccases sensu stricto, namely novel laccases (NLAC), new MCO (NMCO) and new laccases with potential ferroxidase activity (NLF). Additionally, several MCOs already described in the literature were reclassified into the updated groups.

Biomimetically Engineering Valency in Copper Aerogel Toward Efficient Laccase-Mimicking Nanozyme

Developing nanozymes with high intrinsic activity to bridge the gap with natural enzymes has received unremitting attention. In this study, inspired by the copper active center for natural laccase and the multivalent characteristic of Cu, the valence state of Cu-based aerogel is modulated via adjusting the reductant usage for mimicking laccase. The laccase-mimicking activity is well-tailored via valence state manipulation, and theoretical calculations unveil the mechanism that the Cu0 and CuI species enhance the substrate adsorption capability and the CuII species are paramount to lowering the activation barrier synergistically. Heterogeneous metals are further incorporated to promote the valency-conversion of Cu and biomimetic electron transfer, conferring the constructed CuPt7.5% aerogel nanozyme with an ultralow detectable limit of 1 nm for phenolic pollutants. This work highlights the multivalence of Cu on laccase-mimicking activity and provides insights into the underlying catalytic mechanism, shedding light on the rational design of high-performance nanozymes for practical application.

Two novel laccase-like nanozymes based on azole ligands for constructing pH-dependent sensor array for recognizing halogenated phenolic pollutants

Halogenated phenolic compounds are widely used in industrial processes such as paper manufacturing and pesticide production. They are priority pollutants that need to be controlled and are discharged with industrial wastewater. Halogenated phenolics have much greater environmental impacts than phenolics due to elevated toxicity and reduced biodegradability caused by halogen substitution. Since the type and location of halogens have great influence on their toxicity and existing differentiation methods rely on large-scale instruments, there is an urgent need to develop new and convenient sensing technologies for the simultaneous identification and detection of halogenated phenols (including fluorophenols, chlorophenols and bromophenols) for more targeted pollution control. In this work, we prepared two novel laccase-like nanozymes using asymmetric azole ligands (thiazole-2-carboxylic acid and imidazole-2-carboxylic acid) coordinated with Cu2+, and constructed a four-channel sensor array by taking advantage of the difference in their ability to catalyze the color development of halogenated phenols and 4-aminoantipyrine under pH = 7 and pH = 8 conditions. The sensor array was able to accurately discriminate eight halogenated phenols in the range of 5-100 μM, and allowing for accurate quantitative analysis. The method has good anti-interference ability to other non-target phenols, and can realize accurate differentiation of halogenated phenols in real water bodies. Even in the presence of high concentrations of common ions or heavy metal ions, halogenated phenolic pollutants can be accurately identified. The good stability and anti-interference ability make the senor array has a great potential for application and is expected to provide a basis for environmental pollution control.

Recent Progress on the Rational Design of Laccase Mimics

Laccase, a type of copper-containing natural oxidase, is known as a green catalyst because only water was produced as the reduction product. It has shown great potential for applications in wastewater treatment, dye degradation, food and pharmaceutical industries, biosensors, and other fields. Despite the above advantages of natural laccase, challenges arise from its inherent instability, recovery difficulties, and the associated high costs exist. To address such issues, a plethora of nanomaterials that possess laccase-mimicking activity, ranging from monometallic ions-containing nanomaterials to multimetal-based composites, was discovered in the past decade. In general, these materials demonstrate considerable performance variability. A comprehensive understanding of the design principles to achieve high laccase-like activity, particularly those on the Cu2+-involved structures and the related electron transfer, is thus demanded. Therefore, in this review, the structure-activity relationship of native laccase was first summarized, followed by the categorization of the recent design strategies of laccase-like nanozymes. After distilling the insights from the currently reported laccase-mimicking nanomaterials, a further prospect on the rational design of laccase mimics with high efficiency in the future was also proposed.

Exploring Catechol Binding to Laccase with Insights into Enzyme Dynamics for Biosensing Applications

There is growing interest in using enzymatic sensors and bioreactors for detecting and removing toxic compounds. Phenolic pollutants like catechol are a major concern, and laccase, a versatile oxidase, has been widely employed for catechol degradation due to its strong binding affinity. In this study, we reconstruct the binding mechanism of catechol to laccase from the white-rot fungus Trametes versicolor using molecular dynamics simulations, free-energy calculations, Markov state modeling (MSM), and transition path theory (TPT). Our approach identifies five distinct macrostates, offering atomic-level insights into the structural and energetic landscape of the laccase-catechol interaction. Critical transition states and intermediates were characterized, emphasizing the role of the active site loop (A161-F162-P163-L164) and a gate mechanism involving neighboring residues. TPT analysis further quantified transitions among macrostates, revealing two dominant pathways that guide catechol from the unbound state to the active site through sequential and cooperative conformational changes.

S-Modified MOF Nanozyme Cascade System with Multi-Enzyme Activity for Dual-Mode Antibiotic Assay

The judicious utilization of antibiotics has established a robust bulwark for human health. However, their improper usage has engendered deleterious ramifications on the environment, underscoring the imperative for developing efficacious and cost-effective detection and degradation platforms. This study presents a sulfur-modified iron-cobalt bimetallic single-atom nitrogen-doped carbon catalyst (S-FeCo-NC) with a noncopper active center. In contrast to conventional laccase, which utilizes copper as its active center, the S-FeCo-NC catalyst exhibits multiple enzyme activities, including laccase-like, peroxidase-like, and catalase-like functions, with iron and cobalt serving as the active centers. As a proof of concept, the combined laccase-like and catalase-like functions of S-FeCo-NC were used as independent signal outputs, while a multienzyme cascade dual-mode assay system was designed for the rapid detection of tetracycline (TC) in combination with peroxidase-like enzymes. In this system, oxygen directly participated in the catalytic process of laccase-like as an electron acceptor, while catalase-like peroxidase efficiently catalyzed the production of O2 from H2O2. The elevated concentration of O2 offered a unique advantage for the increased catalytic activity of the laccase-like enzyme, which outputs visually resolved colorimetric signals using stable 4-aminopyridine with oxidized TC. Furthermore, the peroxidase-like activity of S-FeCo-NC catalyzed the generation of OH radicals with strong oxidative properties, and these radicals carried out effective oxidative decomposition of TC. The signal output of the response of the catalytic process was performed using differential pulse cyclic voltammetry, which further improved the sensitivity and accuracy of the detection. The experimental findings demonstrate that the detection system exhibits a favorable response signal to TC within the range of 0.005-500 μM, with its detection range reaching 0.5-500 and 0.005-1.00 μM, respectively, and the detection limit is as low as 0.22 μM and 1.68 nM, respectively. This cascade dual-mode detection system, based on multienzyme activity, has been shown to significantly enhance the catalytic activity of laccase, while also demonstrating stability in a lower detection range. This suggests that it may offer a novel approach for the sensitive detection and degradation of environmental pollutants.

Laccase Functional Analysis: Substrates, Activity Assays, Challenges, and Prospects

Enzyme functional analysis is a multifaceted process that can be used for various purposes, such as screening for specific activities, as well as developing, optimising, and validating processes or final products. Functional analysis methods are crucial for assessing enzyme performance and catalytic properties. Laccase, a well-known blue multi-copper oxidase, holds immense potential in diverse industries such as pharmaceuticals, paper and pulp, food and beverages, textiles, and biorefineries due to its clean oxidation process and versatility in handling a wide range of substrates. Despite its prominence, the use of laccase encounters challenges in selecting appropriate functional analysis substrates and methods. This review delves into the substrates utilised in qualitative and quantitative techniques for laccase activity analysis. Although laccase catalyses mono-electron oxidation of aromatic hydroxyl, amine, and thiol compounds efficiently, using molecular oxygen as an electron acceptor, the review identifies limitations in the specificity of the commonly employed substrates, concerns regarding the stability of certain compounds and highlights potential strategies.

Pyrogallol-Stabilized Iridium Nanoclusters With Laccase-Like Activity for Dual Mode Detection of 2,4-Dichlorophenol

Metal nanoclusters (MNCs) have attracted widespread attention due to their unique subnanometer size, tunable fluorescence emission, and excellent biocompatibility. However, the enzyme-like activity and the optical properties of MNCs are rarely exploited simultaneously. Here, iridium nanoclusters (Py-IrNCs) with excellent fluorescence properties and the laccase-like activity were synthesized by the reduction of IrCl3 with NaBH4 in the presence of pyrogallol. The laccase activity of Py-IrNCs exhibited in the catalytic transformation of 2,4-dichlorophenol (2, 4-DP) is substantially superior to that of natural laccase, which is manifested by the fact that the amount of Py-IrNCs was only 2.5% of natural laccase to achieve the same catalytic performance. In the coexisting of 4-aminoantipyrine (4-AP), a distinct color change and quench of fluorescence were observed; thus, a sensitive colorimetric and fluorescence dual-mode determination of 2,4-DP was achieved with a linear range of 0-40 μM and a limit of detection of 0.5 μM. The dual-mode detections can be mutually verified, which effectively improved the reliability of the analysis, demonstrating a promising application potential of Py-IrNCs in pollutant determination.

Beyond Phenolics: Alternative Substrates for Type III Copper Enzymes

The type III copper enzyme family of tyrosinases (TYRs) catalyzes the ortho-hydroxylation and oxidation of phenols as well as the two-electron oxidation of catechols to ortho-quinones. TYRs use copper ions as their tightly bound cofactors and utilize molecular oxygen as their cosubstrate. They are responsible for physiologically important reactions like the formation of melanin, the primary pigment animals apply for protection against UV light. While the reactivity of TYRs on substrates containing aromatic hydroxy groups (i. e. phenols) is well recognized, reports clearly demonstrating that TYRs are active on aromatic amines as well have gone largely unnoticed. In this perspective we aim to bring together the sparse data on non-phenolic TYR substrates to illustrate the potential of TYRs for the oxidation of aminophenols and anilines. The activity of TYRs on aromatic amines extends the substance classes amenable to biotechnological production with TYRs from catechols to N-phenyl imines and phenoxazinone derivates and calls for the inclusion of TYRs among the candidates for oxidative modification of aromatic amines in metabolic pathways.

Laccase based per- and polyfluoroalkyl substances degradation: Status and future perspectives

Per- and polyfluoroalkyl substances (PFAS) with stable carbon-fluorine bonds are used in a wide range of industrial and commercial applications. Due to their extreme environmental persistence, PFAS have the potential to bioaccumulate, cause adverse effects, and present challenges regarding remediation. Recently, microbial and enzymatic reactions for sustainable degradation of PFAS have gained attention from researchers, although biological decomposition of PFAS remains challenging. Surprisingly, laccases, the multi-copper oxidases produced by various organisms, showed potential for PFAS degradation. Mediators play key roles in initiating laccase induced PFAS degradation and defluorination reactions. The laccase-catalyzed PFAS degradation reactions are relatively slower than normal biocatalytic reactions and the low activity of native laccases constrains their capacity to complete defluorination. With their low redox potential and narrow substrate scope, an innovative remediation strategy must be taken to accelerate this reaction. In this review we have summarized the status, challenges, and future perspectives of enzymatic PFAS degradation. The knowledge of laccase-based defluorination and the molecular basis of the reaction mechanisms overviewed in this study could inform future applications of laccases for sustainable PFAS remediation.

Influence of internal electrostatics on reduction potentials in amine-ligated bimetallic copper complexes

The electrostatic modulation of redox potentials of molecular electrocatalysts is a promising strategy to minimize overpotentials without compromising their catalytic activity given their intrinsic correlation. While the introduction of s-block cations to modulate the redox potential of single-site transition metal catalysts is known, the prevalence and nature of such electrostatic interactions in bimetallic complexes deserves further attention. In this work, using density functional theory and electrostatic charged sphere models, we quantify the influence of distance-dependent electrostatic effects on the reduction potentials of a bimetallic Cu(II) model system with a dipicolylamine (DPA) ligand, wherein the Cu(II) centers are bridged by an aliphatic diamine (NH2-(CH2)n-NH2) linker of varying chain lengths (n = 0 to 10). The calculated reduction potentials in non-aqueous solvation environments were found to vary linearly with the reciprocal of the Cu-Cu distance with a slope of 4.1 V Å, and span more than 500 mV, suggesting a strong distance-dependent coulombic electrostatic interaction between the two metal centers. The effect of chemical perturbations to the primary coordination sphere on the distance-dependent electrostatic effects, viz. nature of the metal ion, overall charge and ligand field, was quantified. The in silico predicted shifts in the one-electron redox potential as a function of the chain length in the model system were experimentally validated with the synthesis and cyclic voltammetry studies of two bimetallic Cu(II)(DPA) complexes bridged by 1,4-diaminobutane and 1,8-diaminooctane in acetonitrile.

Pathway-Dependent Catalytic Activity of Short-Peptide-Based Metallozyme: From Promiscuous Activity to Cascade Reaction

Many natural enzymes contain metal ions as cofactors in the active site for biological activity. However, the pathway of the introduction of metal ions in the earliest protein folds for the emergence of higher catalytic activity remains an intriguing open question. Herein, we demonstrate that pathway-dependent self-assembly of short-peptide-based metallozymes results in differences in catalytic activity. Short-peptide-based amyloids with solvent exposed arrays of colocalized catalytic units are able to bind highly soluble Cu2+ ions to demonstrate oxidase-like and RNase-like activity (promiscuity). Further, the metallozyme was able to exhibit higher hydrolase-oxidase cascade activity compared to the mixture of natural enzymes, esterase, and laccase. The collaboration between short-peptide-based amyloid microphases and metal ions suggests that metallozymes might have played a pivotal role in early metabolic processes and biopolymer evolution on the prebiotic earth.

Active site-inspired multicopper laccase-like nanozymes for detection of phenolic and catecholamine compounds

Phenolic compounds are typical organic pollutants which cause severe human health problems due to their teratogenesis, carcinogenesis, neurotoxicity, immunotoxicity and endocrine disruption. Natural laccase is a multicopper oxidase existing in bacteria, plants, and insects, which can accelerate the transformation of phenolic compounds to their less hazardous oxidized products under mild conditions without harmful byproducts. Despite eco-environmentally friendly property of laccase, it still faces constraints of widespread application attribute to its high cost, complex preparation, and vulnerability. Therefore, exploring laccase mimics with high catalytic activity attracts a lot of attention and endeavors. In this research, copper-based nanozymes were prepared with coordination of copper ions and imidazole for mimicking the active sites of natural laccase via solvothermal method. The obtained Cu-based (Cu-Im) nanozymes exhibited multiple redox valence states of Cu and laccase-mimicking coordination structures, which endow Cu-Im with high laccase-like activity. During the process of catalytic oxidation reactions, singlet oxygen and superoxide anions generated from oxygen. Encouraged by the catalytic property, Cu-Im was utilized in degradation and detection of phenolic and catecholamine compounds. The catalytic degradation of compounds by Cu-Im showed good conversion and substrate versatility, which can be used as a kind of potential materials for phenolic pollutant degradation and remediation. Simultaneously, colorimetric sensors of phenols and catecholamines based on Cu-Im in solution system and POCT pad platform were constructed which indicated wide linear range and low limit of detection for both detection strategies. The Cu-Im-based sensor was a promising method for sensitive, fast, convenient, and qualitative-quantitative colorimetric analysis of phenols and catecholamines. The outcomes of this research elucidate Cu-Im is a satisfactory substitute for natural laccase, which will have broad application prospects in laccase-related fields, such as environmental recovery, pollution monitoring, and diagnosis of neurological diseases etc.

Substitution of the Axial Type 1 Cu Ligand Affords Binding of a Water Molecule in Axial Position Affecting Kinetics, Spectral, and Structural Properties of the Small Laccase Ssl1

Multicopper oxidases use Cu ions as cofactors to oxidize various substrates. High reduction potential at Type 1 Cu is considered as crucial for effective catalysis. Previous studies have shown that replacing the axial methionine ligand of the Type 1 Cu with leucine or phenylalanine leads to an increased reduction potential, but not always to higher enzyme activity. Here we present a study on six variants of the small laccase Ssl1 from Streptomyces sviceus, where the axial methionine ligand was substituted, and the effect of the axial ligand on reduction potential, activity, spectral properties and structure was investigated. Absorption, electronic circular dichroism and EPR spectra revealed the presence of a stronger coordinating axial ligand like oxygen, which influences the electronic and catalytic properties more than the nature of the amino acid side chain. The crystal structures of the Ssl1 variants were solved, which show that none of the amino acid side chains coordinate to the Cu. Instead, a water molecule is found in the axial coordination site, which support the spectroscopic data. Our findings highlight the importance of combining structural and spectroscopic methods to investigate the effect of amino acid exchange on multicopper oxidases.

Structure-Function Relationship of the β-Hairpin of Thermus thermophilus HB27 Laccase

Thermus thermophilus HB27 laccase (Tth-Lac) is a thermostable enzyme that contains a β-hairpin (Ala292-Gln307) covering the substrate entrance. We analyzed the role of this β-hairpin in the enzymatic activity of Tth-Lac through three β-hairpin mutants: two variants without the β-hairpin (C1Tth-Lac and C2Tth-Lac) and one with a partially modified β-hairpin (P1Tth-Lac). Enzymatic activity was assayed with different substrates with and without copper. C1Tth-Lac showed a higher dependency on copper, increasing its activity by 1600-fold for syringaldazine (SGZ). All mutants presented a higher activity than Tth-Lac with phenolic substrates in the presence of copper. The position of the signal associated with CuT2 also changed, as shown in EPR spectra. Elucidation of the crystal structure of P1Tth-Lac mutant (PDB: 9CPM) showed that the partial deletion of the β-hairpin did not significantly affect the overall tertiary structure compared to the wild-type (PDB: 2xu9) nor the coordination of the four internally bound Cu atoms. Higher B-factors of the residues downstream of the deletion indicate increased flexibility (Q307, G308, P309, S310) that were otherwise more ordered in the Tth-Lac structure. Redox potential experiments on platinum electrodes have shown that all proteins have high redox potential, a finding that could have significant implications in the field of protein research.

In Crystallo O2 Cleavage at a Preorganized Triiron Cluster

In Nature, the four-electron reduction of O2 is catalyzed at preorganized multimetallic active sites. These complex active sites often feature low-coordinate, redox-active metal centers precisely positioned to facilitate rapid O2 activation processes that obviate the generation of toxic, partially reduced oxygen species. Very few biomimetic constructs simultaneously recapitulate the complexity and reactivity of these biological cofactors. Herein, we report solid-state O2 activation at a triiron(II) active site templated by phosphinimide ligands. Insight into the structure of the O2 reduction intermediates was obtained via in crystallo O2 dosing experiments in conjunction with spectroscopic, structural, magnetic, and computational studies. These data support the in situ formation of an Fe2IIIFeIV-dioxo intermediate upon exposure to O2 that participates in oxygen atom and hydrogen atom transfer reactivity with exogenous substrates to furnish a stable FeIIFe2III-oxo species. Combined, these studies provide an extraordinary level of detail into the dynamics of bond-forming and -breaking processes operative at complex multimetallic active sites.

Influence of Ligand Complexity on the Spectroscopic Properties of Type 1 Copper Sites: A Theoretical Study

Multi-copper oxidases (MCOs) are enzymes of significant interest in biotechnology due to their efficient catalysis of oxygen reduction to water, making them valuable in sustainable energy production and bio-electrochemical applications. This study employs time-dependent density functional theory (TDDFT) to investigate the electronic structure and spectroscopic properties of the Type 1 (T1) copper site in Azurin, which serves as a model for similar sites in MCOs. Four model complexes of varying complexity were derived from the T1 site, including 3 three-coordinate models and 1 four-coordinate model with axial methionine ligation, to explore the impact of molecular branches and axial coordination. Calculations using ωB97X-D3 functional, def2-TZVP basis set, and conductor-like polarizable continuum model (CPCM) solvation model reproduced key experimental spectral features, with increased model complexity improving agreement, particularly for the ~400 cm-1 band splitting in resonance Raman spectra. This work enhances our understanding of T1 copper sites' electronic properties and spectra, bridging the gap between simplified models and complex proteins. The findings contribute to the interpretation of spectroscopic data in blue copper proteins and may inform future studies on similar biological systems.

Cu,Ce-containing phosphotungstates as laccase-like nanozyme for colorimetric detection of Cr(VI) and Fe(Ⅲ)

Herein, a nanocomposite of Cu,Ce-containing phosphotungstates (Cu,Ce-PTs) with outstanding laccase-like activity was fabricated via a one-pot microwave-assisted hydrothermal method. Notably, it was discovered that both Fe3+ and Cr6+ could significantly enhance the electron transfer rates of Ce3+ and Ce4+, along with generous Cu2+ with high catalytic activity, thereby promoting the laccase-like activity of Cu,Ce-PTs. The proposed system can be used for the detection of Fe3+ and Cr6+ in a range of 0.667-333.33 μg/mL and 0.033-33.33 μg/mL with a low detection limit of 0.135 μg/mL and 0.0288 μg/mL, respectively. The proposed assay exhibits excellent reusability and selectivity and can be used in traditional Chinese medicine samples analysis.

Genome-wide identification, classification, and expression profiling of LAC gene family in sesame

BACKGROUND

Laccases (LACs) are vital plant growth and development enzymes, participating in lignin biopolymerization and responding to stress. However, the role of LAC genes in plant development as well as stress tolerance, is still not well understood, particularly in sesame (Sesamum indicum L.), an important oilseed crop.

RESULTS

In this study, 51 sesame LAC genes (SiLACs) were identified, which were unevenly distributed across different chromosomes. The phylogeny of Arabidopsis LAC (AtLACs) subdivided the SiLAC proteins into seven subgroups (Groups I-VII), of which Group VII contained only sesame LACs. Within the same subgroup, SiLACs exhibit comparable structures and conserved motifs. The promoter region of SiLACs harbors various cis-acting elements that are related to plant growth, phytohormones, and stress responses. Most SiLACs were expressed in the roots and stems, whereas some were expressed specifically in flowers or seeds. RNA-seq analysis revealed that 19 SiLACs exhibited down-regulation and three showed up-regulation in response to drought stress, while 15 SiLACs were down-regulated and four up-regulated under salt stress. Additionally, qRT-PCR analysis showcased that certain SiLAC expression was significantly upregulated as a result of osmotic and salt stress. SiLAC5 and SiLAC17 exhibited the most significant changes in expression under osmotic and salt stresses, indicating that they may serve as potential targets for improving sesame resistance to various stresses.

CONCLUSIONS

Our study offers a thorough comprehension of LAC gene structure, classification, evolution, and abiotic stress response in sesame plants. Furthermore, we provide indispensable genetic resources for sesame functional characterization to enhance its tolerance to various abiotic stresses.

Microbial degradation of polyethylene polymer: current paradigms, challenges, and future innovations

Polyethylene (PE) is the second most commonly used plastic worldwide, mainly used to produce single-use items such as bags and bottles. Its significant resistance to natural biodegradation results in the accumulation of PE in landfills, leading to various ecological and toxicological consequences. Despite extensive research on the microbial degradation of PE, achieving complete biodegradation remains a challenge. Comparing experimental outcomes is complicated by the diverse array of microbes involved in PE biodegradation, variations in culture conditions, and differences in assessment tools. This review discusses the critical hurdles in PE biodegradation experiments, including the chemical complexity of PE substrates and the challenges of isolating effective microbes and forming stable consortia. The review also delves into the difficulties in accurately assessing microbial metabolic activity and understanding the biochemical pathways involved in PE degradation. Furthermore, it addresses the pressing issues of metabolic byproducts, slow degradation rates, scalability concerns, and the challenges in measuring biodegradation levels effectively. In addition to outlining the technical challenges associated with PE experiments, this review offers recommendations for future research directions to enhance PE biodegradation outcomes. Overcoming these challenges and implementing the proposed future strategies will improve the reliability, comparability, and practicality of current PE biodegradation experiments, ultimately contributing to better comprehension and management of PE waste in the environment.

Synthesis and application of a phenazine class substrate for high-throughput screening of laccase activity

Biocatalysis is one of the greatest tools for implementing the 12 principles of Green chemistry. Biocatalysts are bio-based, highly efficient and selective, operate at moderate conditions, and can be reused multiple times. However, the wider application of biocatalysts is plagued by a plethora of drawbacks, such as poor stability at operating conditions, inadequate efficiency of catalytic systems, a small number of commercially available biocatalysts, and a lack of substrates or methods for their discovery and development. In this work, we address the lack of suitable substrates for high-throughput screening of laccase by synthesising and investigating a newly developed phenazine-type substrate - Ferbamine. Investigation of Ferbamine pH and thermal stability indicated that its long-term stability in an aqueous medium is superior to that of commercially available substrates and does not require organic solvents. Ferbamine displayed convincing performance in detecting laccase activity on Ferbamine-agar plates in commercial laccase products and the collection of extracts from wild terrestrial fungi (42 species, 65 extracts), of which 26 species have not been described to have laccase activity prior to this work. Incubation of microorganisms on Ferbamine-agar plates showed its compatibility with live colonies. Ferbamine proved to be an easy-to-use substrate, which could be a great addition to the toolbox of methods for the functional analysis of laccases.

Thermophilic lignin-based laccase nanozyme with CuNx center for the detection of epinephrine and degradation of phenolic pollutants

Natural laccases are a family of multi‑copper oxidases that can oxidize multiple phenol substrates and of great importance to contaminant remediation and biosensing. However, the construction of substitutes for the expensive and perishable laccase used in harsh conditions remains a great challenge. Here, we reported a novel strategy for the fabrication of copper-doped lignin-based laccase nanozymes (Cu-AL) through the coordination of aminated lignin and different copper sources. The Cu-AL prepared from CuSO4, possessed highest Cu content and Cu+ proportion, exhibited the best laccase-like activity to various phenols degradation. Strikingly, the thermophilic Cu-AL exhibited superior catalytic activity at 100 °C (3.23 times than that of 60 °C) and durability (> 50 % activity even after 160 days stored in water). Furthermore, a smartphone-based detection platform was successfully developed to achieve the rapid, convenient, and accurate detection of epinephrine concentration. In summary, this work provides a new sustainable and low-cost way to design robust laccase nanozymes from lignocellulose biomass, especially for expanding the applications of enzymatic reaction with high-temperature operation and/or long-term storage in environmental remediation and biosensing.

Protein Quakes in Redox Metalloenzymes: Clues to Molecular Enzyme Conductivity Triggered by Binding of Small Substrate Molecules

Multicentre redox metalloproteins undergo conformational changes on electrochemical surfaces, or on enzyme substrate binding. The two-centre copper enzymes, laccase (Type I and TypeII/III Cu) and nitrite reductase (CuNIR) (Type I and Type II Cu) are examples. With some exceptions, these enzymes show no non-turnover voltammetry on Au(111)-surfaces modified by thiol based self-assembled molecular monolayers, but dioxygen or nitrite substrate triggers strong electrocatalytic signals. Scanning tunnelling microscopy also shows high conductivity only when dioxygen or nitrite is present. Atomic force microscopy shows constant CuNIR height but pronounced structural expansion in the electrocatalytic range on nitrite binding. We have recently offered a rationale, based on ab initio quantum chemical studies of water/nitrite substitution in a 740-atom CuNIR fragment. Presently we provide much more detailed structural assignment mapped to single-residue resolution. NO2 --binding induces both a 2 Å Cu-Cu distance increase, and pronounced frontier orbital delocalization strongly facilitating ET between the Cu regions. The conformational changes transmit from the catalytic Type II centre to the electron inlet Type I centre, via the His129-Cys130 ligands, and via Type I-Cys130 or Type I-His129 ending at Type II Asp92. The ET patterns are reflected in different atomic Mulliken charges in the water and nitrite CuNIR fragment.

Tyrosinases: a family of copper-containing metalloenzymes

Tyrosinases (TYRs) are a family of copper-containing metalloenzymes that are present in all domains of life. TYRs catalyze the reactions that start the biosynthesis of melanin, the main pigment of the animal kingdom, and are also involved in the formation of the bright colors seen on the caps of mushrooms and in the petals of flowers. TYRs catalyze the ortho-hydroxylation and oxidation of phenols and the oxidation of catechols to the respective o-quinones. They only need molecular oxygen to do that, and the products of TYRs-o-quinones-are highly reactive and will usually react with the next available nucleophile. This reactivity can be harnessed for pharmaceutical applications as well as in environmental and food biotechnology. The majority of both basic and applied research on TYRs utilizes "mushroom tyrosinase", a crude enzyme preparation derived from button mushroom (Agaricus bisporus) fruiting bodies. Access to pure TYR preparations comes almost exclusively from the production of recombinant TYRs as the purification of these enzymes from the natural source is usually very laborious and plagued by low yields. In this text an introduction into the biochemistry of the enzyme TYR will be given, followed by an overview of available structural data of TYRs, the current model for the catalytic mechanism, a survey of reports on the recombinant production of this important metalloenzyme family, and a review of the applications of TYRs for the synthesis of catechols, as biosensors, in bioremediation, for the cross-linking of proteins and medical hydrogels as well as for melanoma treatment.

Graphical Abstract

Enzymatic Routes to Designer Hemicelluloses for Use in Biobased Materials

Various enzymes can be used to modify the structure of hemicelluloses directly in vivo or following extraction from biomass sources, such as wood and agricultural residues. Generally, these enzymes can contribute to designer hemicelluloses through four main strategies: (1) enzymatic hydrolysis such as selective removal of side groups by glycoside hydrolases (GH) and carbohydrate esterases (CE), (2) enzymatic cross-linking, for instance, the selective addition of side groups by glycosyltransferases (GT) with activated sugars, (3) enzymatic polymerization by glycosynthases (GS) with activated glycosyl donors or transglycosylation, and (4) enzymatic functionalization, particularly via oxidation by carbohydrate oxidoreductases and via amination by amine transaminases. Thus, this Perspective will first highlight enzymes that play a role in regulating the degree of polymerization and side group composition of hemicelluloses, and subsequently, it will explore enzymes that enhance cross-linking capabilities and incorporate novel chemical functionalities into saccharide structures. These enzymatic routes offer a precise way to tailor the properties of hemicelluloses for specific applications in biobased materials, contributing to the development of renewable alternatives to conventional materials derived from fossil fuels.

A novel and facile oxygen-activated time-temperature indicator with wide temperature monitoring range and good stability based on the laccase-like nanozyme

BACKGROUND

Time-Temperature Indicator (TTI) is an indicator device for real-time monitoring of the thermal history of the product. Due to the enzymatic reactions are affected by both time and temperature, enzymatic TTIs have been extensively studied and developed in recent years. However, enzymatic TTIs contain biologically active molecules (enzymes), which require high storage and use conditions. Most of them are designed to mix the system species together and irreversible reaction is undertaken. Nanozymes are the synthetic nanomaterials with similar biocatalytic functions as natural enzymes, which have extensive applications in analytical chemistry, biosensing, and environmental protection due to their facile synthesis, low cost, high stability and durability.

RESULTS

This work proposed to replace the natural laccase to laccase-like nanozyme, designed a novel and facile O2-activated time-temperature indicator for the first time. Nanozyme had excellent thermal and storage stability, which could maintain fabulous catalytic activity in the wide temperature range of 10-80 °C and after a long-term storage. Based on the O2 was required to participate in the oxidation of laccase-catalyzed substrates, a squeeze-type O2-activated TTI was designed by controlling O2 in the TTI system. The TTI was activated through extruding the O2-coated airbag ruptured and producing an irreversible color reaction. Combined with a smartphone to extract the chromaticity for portable visual real-time monitoring. Five sets of TTIs were prepared based on the concentration of nanozyme, and the activation energies (Ea) ranging from 28.45 to 72.85 kJ mol-1, which were able to be fitted to products with Ea ranging from 3.45 to 97.8 kJ mol-1 and the monitoring-time of less than 7 days.

SIGNIFICANCE

Compared to the traditional enzymatic TTI, the TTIs designed based on nanozyme has the advantages of controlled activation, wider temperature monitor range and good stability. Providing a new approach to the development of real-time monitoring of smart devices.

In Vitro and Computational Response of Differential Catalysis by Phlebia brevispora BAFC 633 Laccase in Interaction with 2,4-D and Chlorpyrifos

Enzymes secreted by white rot fungi (WRF), such as laccase, offer a promising approach for the treatment of hazardous xenobiotic compounds. This study conducted a comprehensive analysis of the impact of the pesticides 2,4-dichlorophenoxyacetic acid (2,4-D) and chlorpyrifos on the laccase of Phlebia brevispora BAFC 633 through in vitro and bioinformatics analyses. The fungal strain was shown to be tolerant to both pesticides, with notable morphological and ultrastructural alterations in the mycelium. Laccase activity and two isoenzymes (53 and 70 kDa) were detected in all initial treatments. The laccase was concentrated for subsequent catalytic evaluation in the presence of both pesticides, showing high stability at a pH of 3.6 and a temperature range of 50-60 °C. The lacI gene, corresponding to this laccase, was modeled, and its structure revealed a defined catalytic pocket validated with a drug score of 0.61. Molecular docking estimated affinity energies of -5.06 and -9.41 Kcal mol-1 for 2,4-D and chlorpyrifos, respectively. Molecular Mechanics Poisson-Boltzmann Surface Area (MM/PBSA) analysis through 250 ns of molecular dynamics revealed stronger hydrophobic interactions of laccase with chlorpyrifos and highlighted the importance of residue His460 in stabilizing both complexes. Understanding the impact of these agrochemicals on the catalytic function of laccase is crucial for developing future biotechnological strategies involving this enzyme.

Building hydrophobic substrate pocket to boost activity of laccase-like nanozyme through acetonitrile-mediated strategy

Nanozymes, as promising alternatives to natural enzymes, offer several advantages with biocatalytic functions but remain inferior in catalytic activity. It is crucial to focus on factors that affect the enzymatic activity of nanozymes and develop strategies to make them more competitive with natural enzymes. Herein, CuV2O5 nanorods are confirmed to own the intrinsic laccase-like activity, and an acetonitrile (MeCN)-mediated strategy is proposed for reaction acceleration by mimicking the enzymatic substrate pocket. In the presence of MeCN, the interaction between substrates and nanozymes gets efficiently promoted by the bridging function of cyano-group, where the utilization of Cu active sites is greatly improved due to the condensed hydrophobic substrate layers formed in the vicinity of CuV2O5 nanorods by the solvent effect of MeCN. Theoretical calculations also disclose that the addition of MeCN endows 2,4-dichlorophenol (2,4-DP) with a lower free-energy barrier in adsorption and activation on the surface of CuV2O5 nanozyme. Benefiting from the improved activity, a sensitive colorimetric sensing platform for 2,4-DP is constructed with the limit of detection as low as 0.48 μM. Our finding lays a theoretical foundation for achieving high-performance catalytical activity of the nanozymes based on the modulation of the reaction microenvironment, effectively alleviating the complex engineering process of nanozymes.

Identification of Laccase Family of Auricularia auricula-judae and Structural Prediction Using Alphafold

Laccase is an enzyme that plays an important role in fungi, including lignin degradation, stress defense, and formation of fruiting bodies. Auricularia auricula-judae is a white-rot fungus in the Basidiomycota phylum, capable of delignifying wood. In this study, seven genes belonging to the laccase family were identified through de novo sequencing, containing Cu-Oxidase, Cu-Oxidase_2, and Cu-Oxidase_3 domains. Subsequently, the physical characteristics, phylogenetic relationships, protein secondary structure, and tertiary structure of the laccase family (AaLac1-AaLac7) were analyzed. Prediction of N-glycosylation sites identified 2 to 10 sites in the laccase family, with AaLac7 having the highest number of sites at 10. Sequence alignment and analysis of the laccase family showed high consistency in signature sequences. Phylogenetic analysis confirmed the relationship among laccases within the family, with AaLac3-AaLac4 and AaLac5-AaLac6 being closely positioned on the tree, exhibiting high similarity in tertiary structure predictions. This study identified and analyzed laccase family genes in Auricularia auricula-judae using de novo sequencing, offering a simple method for identifying and analyzing the laccase family in organisms with unknown genetic information.

Impact of surface-active ionic solutions on the structure and function of laccase from trametes versicolor: Insights from molecular dynamics simulations

Many protein-ionic liquid investigations have examined laccase interactions. Laccases are a class of poly-copper oxidoreductases that retain significant biotechnological relevance owing to their notable oxidative capabilities and their application in the elimination of synthetic dyes, phenolic compounds, insecticides, and various other substances. This study investigates the impact of surface active ionic liquids (SAILs), namely, decyltrimethylammonium bromide [N10111][Br] and 1-decyl-3-methylimidazolium chloride [C10mim][Cl] as cationic surfactant ionic liquids and cholinium decanoate [Chl][Dec], an anionic surfactant ionic liquid, on the structure and function of laccase from the fungus Trametes versicolor (TvL) by the molecular dynamics (MD) simulation method. In summary, this study showed that laccase solvent-accessible surface area increased in the ionic liquid [Chl][Dec] while it decreased in the other two ionic liquids. Interestingly, [Chl][Dec] ionic liquid components formed hydrogen bonds with laccase, while [N10111][Br] and [C10mim][Cl] components were unable to form hydrogen bonds with laccase. The quantity of hydrogen bonds formed between water molecules and the enzyme was also diminished in the presence of [Chl][Dec] in comparison to the other two ionic liquids. especially at a concentration of 250 mM. In 250 mM concentrations of [N10111][Br] and [C10mim][Cl], clusters of long-chain cations are likely to form near the copper T1 site. However, even at low [Chl][Dec] concentrations, long [Dec]- chains were observed to penetrate the enzyme near the copper T1 site, and at 250 mM [Chl][Dec], a large cluster of anions occupied the opening of the active site. The results of the analysis also show that the interaction between the [Dec]- anion and the enzyme is stronger than the interaction between [N10111]+ and [C10mim]+ with laccase; in addition, the [Dec]- anion, compared to [Br]- and [Cl]- has a much greater tendency to bind with the enzyme residues.

Copper formate-lysine nanoparticles with polyphenol oxidase-like activity for the detection of epinephrine

Laccase is an enzyme known for its eco-friendly uses in environmental cleanup and biotechnology. However, it has limitations such as low stability, high cost, and complex recycling. So, there is a need for laccase mimics that can effectively imitate its properties. Herein, we created copper formate-lysine nanoparticles (Cuf-Lys) that mimic laccase's activity. The developed Cuf-Lys demonstrated remarkable polyphenol oxidase-like activity, stability, and recyclability, making them suitable for the fabrication of efficient colorimetric sensors for the detection of epinephrine. These sensors had a specific response and could accurately measure epinephrine concentrations ranging from 2.5 to 50 μM, with a detection limit as low as 1 μM. Furthermore, the biosensor demonstrated high sensitivity and selectivity when applied to the detection of rutin. The limit of detection for rutin was determined to be 0.16 μM while in the linear concentration range of 0.25 to 150.0 μM. We believe that Cuf-Lys provide a new route for the design of laccase mimics, showing potential applications for biomedical diagnosis and environmental monitoring.

Expression of laccase and ascorbate oxidase affects lignin composition in Arabidopsis thaliana stems

Lignin is a phenolic polymer that is a major source of biomass. Oxidative enzymes, such as laccase and peroxidase, are required for lignin polymerisation. Laccase is a member of the multicopper oxidase family and has a high amino acid sequence similarity with ascorbate oxidase. However, the process of functional differentiation between the two enzymes remains poorly understood. In this study, the common ancestry sequence of laccase and ascorbate oxidase (AncMCO) was predicted via phylogenetic reconstruction, and its in vivo effect on lignin biosynthesis in Arabidopsis thaliana was assessed. The estimated AncMCO sequence conserved key residues that coordinate with copper ions, implying that the electron transfer system is likely to be conserved in AncMCO. However, multiple insertions/deletions corresponding to protein surface structures have been found between laccase, ascorbate oxidase, and AncMCO. The overexpression of canonical laccase (AtLAC4) and ascorbate oxidase (AtAAO1) in A. thaliana resulted in notable increases of syringyl/guaiacyl lignin unit ratio in stems, whereas, in contrast, the overexpression of AncMCO did not show any detectable change in lignin deposition. Transcriptomic analysis revealed that the AtAAO1-overexpressing line exhibited significant changes in the expression of a wide range of cell wall biosynthesis genes. These results highlight the importance of the molecular evolution of multicopper oxidase, which drives lignin biosynthesis during plant evolution.

Recent advances in the role of biocatalyst in biofuel cells and its application: An overview

Biofuel cells have recently gained popularity as a green and renewable energy source. Biofuel cells are unique devices of energy and are capable of converting the stored chemical energy from waste materials such as pollutants, organics and wastewater into reliable, renewable, pollution-free energy sources through the action of biocatalysts such as various microorganisms and enzymes. It is a promising technological device to treat waste to compensate for global warming and the energy crisis through the green energy production process. Due to their unique properties, various potential biocatalysts are attracting researchers to apply them to various microbial biofuel cells for improving electricity and power. Recent research in biofuel cells is focusing on the exploitation of different biocatalysts and how they are enhancing power generation for various applications in the field of environmental technology, and biomedical fields such as implantable devices, testing kits, and biosensors. This review focusing the importance of microbial fuel cells (MFCs) and enzymatic fuel cells (ECFs) and role of different types of biocatalysts and their mechanisms for improving biofuel cell efficiency gathered from recent reports. Finally, its multifaceted applications with special emphasis on environmental technology and biomedical field will be described, along with future perspectives.

Cellulose / waste Cu2+-activated carbon composite: A sustainable and green material for boosting laccase activity and degradation of bisphenol A in wastewater

Low enzyme activity is one of the disadvantages of immobilized laccase. In this study, waste Cu2+-loaded activated carbon (Cu-AC) was successfully used in preparing a novel composite support，cellulose / Cu2+-loaded activated carbon beads (C / Cu-AC)， and effectively boosted immobilized laccase activity. To achieve optimum conditions for immobilization of laccase, the immobilization time, pH and laccase concentration were examined. The highest immobilized laccase activity (34.21 U/g) was achieved under optimum conditions (T = 4 h, pH = 4, C = 5 g/L), which was increased by 35.86 % compared to control. In addition, the immobilized laccase showed an outstanding performance in thermostability and reusability compared to free laccase. Moreover, the degradation of BPA by immobilized laccase was carried out, and the optimum degradation conditions were explored. Under such conditions: concentration of BPA was 75 mg / L and pH = 4, t = 1 h, T = 50 °C，the removal yield of BPA reached a maximum of 79.88 %. Therefore, the utilization of waste Cu-CA is a powerful method to boost immobilized laccase activity and creating a new way to high value treatment of waste Cu-CA.

In Silico Identification of the Laccase-Encoding Gene in the Transcriptome of the Amazon River Prawn Macrobrachium amazonicum (Heller, 1862)

BACKGROUND

Macrobrachium amazonicum is an opportunistic and omnivorous species that primarily feeds on plant material. Recent studies have shown that Endo-β-1,4-glucanase and Endo-β-1,4-mannanase are expressed in the transcriptome of adult specimens, while juveniles are capable of digesting nutrients from purified cellulose in their diet. In organisms that degrade raw plant material, laccase plays a key role in oxidizing phenolic compounds found in lignin, leading to its depolymerization and increasing access to cellulose and hemicellulose microfibrils.

OBJECTIVE

In this study, we conducted an in silico identification and characterization of the laccase-encoding gene, as this enzyme is linked to lignin biodegradation in herbivorous crustaceans.

METHODS

We analyzed the transcriptomes of the hepatopancreas from adult M. amazonicum, sequenced using the Illumina HiSeq 2500 platform. Subsequently, bioinformatics analyses were conducted to predict the conserved regions and active sites associated with laccase activity.

RESULTS

A complete open reading frame (ORF) of the laccase protein was identified in all datasets, comprising 609 amino acids. The top 40 similarity hits corresponded exclusively to crustaceans such as prawns, crayfish, and crabs (86.3-51.4%), while the highest divergence was observed in relation to fungi, plants, and bacteria. Three conserved domains were detected, along with the complete set of copper-binding centers (T1Cu, T2Cu, and T3Cu). A notable variable residue was methionine, suggesting a reduced redox potential in M. amazonicum laccase.

CONCLUSION

These findings, combined with recent reports on the nutritional requirements of M. amazonicum, contribute to a deeper understanding of the digestive physiology of this species and offer valuable insights into its ability to utilize plant fibers as energy sources.

Mutations of methionine 444 interacting with T1Cu-coordinating amino acids affect the structure and function of multicopper oxidase CopA

Manganese is an essential trace element for humans, animals, and plants, but excessive amounts of manganese can cause serious harm to organisms. The biological manganese oxidation process mainly oxidizes Mn(II) through the secretion of unique manganese oxidase by manganese-oxidizing bacteria. The T1 Cu site of multicopper oxidase is the main site for substrate oxidation, and its role is to transfer electrons to TNC, where dioxygen reduction occurs. In this study, methionine (Met) No. 444 interacting with the T1Cu-coordinating amino acid in the multicopper oxidase CopA from Brevibacillus panacihumi MK-8 was mutated to phenylalanine (Phe) and leucine (Leu) by the enzyme. Based on the analysis of enzymatic properties and the structural model, the mutant protein M444F with 4.58 times the catalytic efficiency of the original protein CopA and the mutant protein M444L with 1.67 times the catalytic efficiency of the original protein CopA were obtained. The study showed that the manganese removal rate of the manganese-oxidizing engineered bacterium Rosetta-pET-copAM444L cultured for 7 days was 88.87%, which was 10.77% higher than that of the original engineered bacterium. Overall, this study provides a possibility for the application of genetic engineering in the field of biological manganese removal.

Emerging Roles of Nanozymes in Plant and Environmental Sectors

The demand for food has increased dramatically as the global population increases, putting more strain on the sustainability of agriculture. To fulfill this requirement, it is imperative to develop brand-new technologies. The application potential of nanozymes in the plant and environmental sectors is progressively becoming apparent as a result of their effective enzymatic catalytic activity and the distinctive characteristics of nanomaterials, including size, specific surface area, optical properties, and thermal properties. Herein, we systematically analyze the catalytic mechanisms of nanozymes with different enzyme-mimetic activities and summarize their applications in improving crop yields by regulating ROS levels and enhancing stress resistance and detecting and removing hazardous pollutants. Finally, we thoroughly analyze the challenges faced by nanozymes regarding size, design, application, economy, and biosafety and look forward to their future development directions to better serve sustainable agriculture.

Cu2(OH)3NO3 nanozyme sensor array for the discrimination of multiple sulfides in food

In the food industry, sulfides are commonly used as preservatives and flavor regulators. However, long-term excessive intake of sulfides can lead to serious health problems. Therefore, developing efficient sulfide detection methods is particularly important. Here, we have effectively synthesized a novel bifunctional copper hydroxide nitrate (Cu2(OH)3NO3) nanozyme with outstanding peroxidase-like and laccase-like behaviors in basic deep eutectic solvents (DES). Because the various types of sulfides have diverse regulatory effects on the two catalytic behaviors of Cu2(OH)3NO3, a two channel nanozyme sensor array based on the peroxidase-like and laccase-like behaviors of Cu2(OH)3NO3 was constructed and successfully used for the identification of six kinds of sulfides (Na2S, Na2S2O3, Na2SO3, Na2SO4, NaHSO3, and Na2S2O8). Remarkably, the sensor array has achieved successful discrimination among six sulfides present in wine, egg, and milk samples. Finally, the sensor array has successfully distinguished and differentiated three actual samples (wine, egg, and milk). This study is of great significance in promoting the efficient construction of array units and improving the effective identification of sulfides in complex food samples.

Laccase surface-display for environmental tetracycline removal: From structure to function

Facing the increasingly prominent tetracycline pollution and the resulting environmental problems, how to find environmental and efficient treatment means is one of the current research hotspots. In this study, the laccase surface-display technology for tetracycline treatment was investigated. Via study, the type of anchoring protein had a minor influence on the laccase ability, while the type of laccase showed a major impact. Bacillus subtilis spore coat protein (CotA) exhibited higher laccase activity, stability, and efficiency in degrading tetracycline than Pleurotus ostreatus laccase 6 (Lacc6). The superiority of bacterial laccase over fungal laccase was elucidated from the perspective of crystal structure. Besides, a variety of technical means were used to verify the success of surface-display. pGSA-CotA surface-displayed bacteria exhibited good tolerance to high temperature, pH, and various heavy metals. Importantly, surface-displayed bacteria showed faster degradation efficiency and better treatment effects than the intracellular expression bacteria in tetracycline degradation. This implies that surface display technology has greater potential for laccase-mediated environmental remediation. Due to the adverse impacts of tetracycline on soil enzyme activity and microorganisms, our study found that pGSA-CotA surface-displayed bacteria can alleviate tetracycline stress in soil and partially activate the soil, thereby increasing soil enzyme activity and certain nitrogen cycling genes.

Enhanced degradation of phenolic pollutants by a novel cold-adapted laccase from Peribacillus simplex

Laccase (EC 1.10.3.2), as eco-friendly biocatalysts, holds immense potential for sustainable applications across various environmental and industrial sectors. Despite the growing interest, the exploration of cold-adapted laccases, especially their unique properties and applicability, remains limited. In this study, we have isolated, cloned, expressed, and purified a novel laccase from Peribacillus simplex (GenBank: PP430751), which was derived from permafrost layer. The recombinant laccase (PsLac) exhibited optimal activity at 30 °C and a pH optimum of 3.5. Remarkably, PsLac exhibited remarkable stability in the presence of organic solvents, with its enzyme activity increasing by 20 % after being incubated in a 30 % trichloromethane solution for 12 h, compared to its initial activity. Furthermore, the enzyme preserved 100 % of its activity after undergoing eight freeze-thaw cycles. Notably, the catalytic center of PsLac contains Zn2+ instead of the typically observed Cu2+ found in other laccases, and metal-ion substitution experiments raised the catalytic efficiency to 3-fold when Zn2+ was replaced with Fe2+. Additionally, PsLac has demonstrated a proficient ability to degrade phenolic pollutants, such as hydroquinone, even at a low temperature of 16 °C, positioning it as a promising candidate for environmental bioremediation and contributing to cleaner production processes.

Enhanced catalytic performance and pH stability of Streptomyces Laccase Y230R and its degradation of malachite green

The escalating threat of malachite green (MG) pollution poses significant risks to ecosystems. Saturation mutation targeting Tyr230 of small laccase (SLAC) from Streptomyces coelicolor yielded Y230R, exhibiting a remarkable 104 % increase in specific activity. Notably, this mutation achieved dual enhancements in both activity and pH stability. Molecular dynamics simulation revealed higher structural stability of Y230R compared to wild-type (WT) across varying pH levels. The increased count of hydrogen bonds in Y230R compared to WT may be contribute to its stability. Y230R demonstrated superior catalytic efficiency (67.0 %) in MG decolorization, maintaining over 90 % activity after 30 min incubation in MG solution (500 mg/L), highlighting enhanced tolerance compared to WT. Molecular docking analysis attributed the differential catalytic effects on MG and ABTS to structural disparities and hydrogen bonding. Y230R stands as a promising composite mutant for future laccase engineering and industrial applications.

Nature-Inspired Strategies for Sustainable Degradation of Synthetic Plastics

Synthetic plastics have become integral to our daily lives, yet their escalating production, limited biodegradability, and inadequate waste management contribute to environmental contamination. Biological plastic degradation is one promising strategy to address this pollution. The inherent chemical and physical properties of synthetic plastics, however, pose challenges for microbial enzymes, hindering the effective degradation and the development of a sustainable biological recycling process. This Perspective explores alternative, nature-inspired strategies designed to overcome some key limitations in currently available plastic-degrading enzymes. Nature's refined degradation pathways for natural polymers, such as cellulose, present a compelling framework for the development of efficient technologies for enzymatic plastic degradation. By drawing insights from nature, we propose a general strategy of employing substrate binding domains to improve targeting and multienzyme scaffolds to overcome enzymatic efficiency limitations. As one potential application, we outline a multienzyme pathway to upcycle polyethylene into alkenes. Employing nature-inspired strategies can present a path toward sustainable solution to the environmental impact of synthetic plastics.

Laccase: Sustainable production strategies, heterologous expression and potential biotechnological applications

Laccase is a multicopper oxidase enzyme that target different types of phenols and aromatic amines. The enzyme can be isolated and characterized from microbes, plants and insects. Its ubiquitous nature and delignification ability makes it a valuable tool for research and development. Sustainable production methods are being employed to develop low cost biomanufacturing of the enzyme while achieving high titers. Laccase have significant industrial application ranging from food industry where it can be used for wine stabilization, texture improvement and detection of phenolic compounds in food products, to cosmetics offering benefits such as skin brightening and hair colouring. Dye decolourization/degradation, removal of pharmaceutical products/emerging pollutants and hydrocarbons from wastewater, biobleaching of textile fabrics, biofuel production and delignification of biomass making laccase a promising green biocatalyst. Innovative methods such as using inducers, microbial co-culturing, recombinant DNA technology, protein engineering have pivotal role in developing laccase with tailored properties. Enzyme immobilization using new age compounds including nanoparticles, carbonaceous components, agro-industrial residues enhance activity, stability and reusability. Commercial formulations of laccase have been prepared and readily available for a variety of applications. Certain challenges including production cost, metabolic stress in response to heterologous expression, difficulty in purification needs to be addressed.

Nucleobase-modulated copper nanomaterials with laccase-like activity for high-performance degradation and detection of phenolic pollutants

Laccases are the most commonly used agents for the treatment of phenolic pollutants. To address the instability and high cost of natural laccases, we investigated nucleobase-modulated copper nanomaterial with laccase-like activity. Various nucleobases, including adenine, guanine, cytosine, and thymine, were investigated as templates for Cu2+ reduction and copper nanomaterials formation due to their coordination capacity. By comparing structure and catalytic activity, the cytosine-mediated copper nanomaterial (C-Cu) had the best laccase-like activity and other nucleobase-templated copper nanomaterials exhibited low catalytic activity under the same conditions. The mechanism of nucleobase regulation of the catalytic activity of copper nanomaterials was further analyzed using X-ray photoelectron spectroscopy and density functional theory. The possible catalytic mechanisms of C-Cu, including substrate adsorption, substrate oxidation, oxygen binding, and oxygen reduction, were proposed. Remarkably, nucleobase-modulated copper nanozymes showed high stability and catalytic oxidation performance at various pH values, temperatures, long-term storage, and high salinity. In combination with electrochemical techniques, a portable electrochemical sensor for measuring phenolic pollutants was developed. This novel sensor exhibited a good linear response to catechol (10-1000 μM) with a limit of detection of 1.8 μM and excellent selectivity and anti-interference ability. This study provides not only a new strategy for the regulation of the laccase-like activity of copper nanomaterials but also a novel tool for the effective removal and low-cost detection of phenolic pollutants.

Discovery of alkaline laccases from basidiomycete fungi through machine learning-based approach

BACKGROUND

Laccases can oxidize a broad spectrum of substrates, offering promising applications in various sectors, such as bioremediation, biomass fractionation in future biorefineries, and synthesis of biochemicals and biopolymers. However, laccase discovery and optimization with a desirable pH optimum remains a challenge due to the labor-intensive and time-consuming nature of the traditional laboratory methods.

RESULTS

This study presents a machine learning (ML)-integrated approach for predicting pH optima of basidiomycete fungal laccases, utilizing a small, curated dataset against a vast metagenomic data. Comparative computational analyses unveiled the structural and pH-dependent solubility differences between acidic and neutral-alkaline laccases, helping us understand the molecular bases of enzyme pH optimum. The pH profiling of the two ML-predicted alkaline laccase candidates from the basidiomycete fungus Lepista nuda further validated our computational approach, showing the accuracy of this comprehensive method.

CONCLUSIONS

This study uncovers the efficacy of ML in the prediction of enzyme pH optimum from minimal datasets, marking a significant step towards harnessing computational tools for systematic screening of enzymes for biotechnology applications.

A facile and on-site sensing strategy for phenolic compounds based on a novel nanozyme with high polyphenol oxidase-like activity

Phenolic compounds (PCs) are diverse in nature and undergo complex migration and transformations in the environment, making it challenging to use techniques such as chromatography and other traditional methods to determine the concentration of PCs by separation, individual monitoring and subsequent addition. To address this issue, a facile and on-site strategy was developed to measure the concentration of PCs using a novel nanozyme with polyphenol oxidase-like activity. First, the nanozyme was designed by coordinating the asymmetric ligand nicotinic acid with copper to mimic the structure of mononuclear and trinuclear copper clusters of natural laccases. Subsequently, by introducing 2-mercaptonicotinic acid to regulate the valence state of copper, the composite nanozyme CuNA10S was obtained with significantly enhanced activity. Interestingly, CuNA10S was shown to have a broad substrate spectrum capable of catalyzing common PCs. Building upon the superior performance of this nanozyme, a method was developed to determine the concentration of PCs. To enable rapid on-site sensing, we designed and prepared CuNA10S-based test strips and developed a tailored smartphone sensing platform. Using paper strip sensors combined with a smartphone sensing platform with RGB streamlined the sensing process, facilitating rapid on-site analysis of PCs within a range of 0-100 μM. Our method offers a solution for the quick screening of phenolic wastewater at contaminated sites, allowing sensitive and quick monitoring of PCs without the need for standard samples. This significantly simplifies the monitoring procedure compared to more cumbersome large-scale instrumental methods.