Aldehyde PEGylation of laccase fromTrametes versicolorin route to increase its stability: effect on enzymatic activity

Research progress on the PEGylation of therapeutic proteins and peptides (TPPs)

With the rapid advancement of genetic and protein engineering, proteins and peptides have emerged as promising drug molecules for therapeutic applications. Consequently, there has been a growing interest in the field of chemical modification technology to address challenges associated with their clinical use, including rapid clearance from circulation, immunogenicity, physical and chemical instabilities (such as aggregation, adsorption, deamination, clipping, oxidation, etc.), and enzymatic degradation. Polyethylene glycol (PEG) modification offers an effective solution to these issues due to its favorable properties. This review presents recent progress in the development and application of PEGylated therapeutic proteins and peptides (TPPs). For this purpose, firstly, the physical and chemical properties as well as classification of PEG and its derivatives are described. Subsequently, a detailed summary is provided on the main sites of PEGylated TPPs and the factors that influence their PEGylation. Furthermore, notable instances of PEG-modified TPPs (including antimicrobial peptides (AMPs), interferon, asparaginase and antibodies) are highlighted. Finally, we propose the chemical modification of TPPs with PEG, followed by an analysis of the current development status and future prospects of PEGylated TPPs. This work provides a comprehensive literature review in this promising field while facilitating researchers in utilizing PEG polymers to modify TPPs for disease treatment.

Enhanced laccase separation from fermentation medium using cryogel columns

The laccase enzyme family belongs to the oxidoreductase enzyme class and is one of the most commercially valuable enzymes that catalyzes the oxidation of one electron of a wide range of phenolic compounds. Separation and purification of laccases are crucial for industry since they play an important role in dye decolorization, biodegradation and food processing. Therefore, developing effective, high yielding and cost-effective methods for laccase production is vital. In this study, it was aimed to prepare cryogel columns for laccase purification following the bioproduction of laccase via Aspergillus niger. 2-hydroxyethyl methacrylate based cryogels were synthesized in the presence of 1-vinylimidazole as the affinity ligand and characterized by swelling tests, Brunauer-Emmett-Teller surface area measurement and scanning electron microscopy analysis. Surface area and water uptake ratio of cryogel columns were 35 m²/g and 93 %, respectively. The effect of pH, equilibrium laccase concentration, flow rate, interaction time and temperature on laccase adsorption were examined. The purification factor was calculated as 10.53 under optimum conditions and the enzyme recovery was found to be 86.7 % from fermentation medium. Current study revealed that laccase purification using cryogels following filtration of fermentation medium could be a promising candidate for industrial applications with eliminating the need for complex chromatographic steps.

Peptide-drug conjugates (PDCs): a novel trend of research and development on targeted therapy, hype or hope?

Peptide-drug conjugates (PDCs) are the next generation of targeted therapeutics drug after antibody-drug conjugates (ADCs), with the core benefits of enhanced cellular permeability and improved drug selectivity. Two drugs are now approved for market by US Food and Drug Administration (FDA), and in the last two years, the pharmaceutical companies have been developing PDCs as targeted therapeutic candidates for cancer, coronavirus disease 2019 (COVID-19), metabolic diseases, and so on. The therapeutic benefits of PDCs are significant, but poor stability, low bioactivity, long research and development time, and slow clinical development process as therapeutic agents of PDC, how can we design PDCs more effectively and what is the future direction of PDCs? This review summarises the components and functions of PDCs for therapeutic, from drug target screening and PDC design improvement strategies to clinical applications to improve the permeability, targeting, and stability of the various components of PDCs. This holds great promise for the future of PDCs, such as bicyclic peptide‒toxin coupling or supramolecular nanostructures for peptide-conjugated drugs. The mode of drug delivery is determined according to the PDC design and current clinical trials are summarised. The way is shown for future PDC development.

Therapeutic Textiles Functionalized with Keratin-Based Particles Encapsulating Terbinafine for the Treatment of Onychomycosis

Onychomycosis is the most common nail fungal infection worldwide. There are several therapy options available for onychomycosis, such as oral antifungals, topicals, and physical treatments. Terbinafine is in the frontline for the treatment of onychomycosis; however, several adverse effects are associated to its oral administration. In this work, innovative keratin-based carriers encapsulating terbinafine were designed to overcome the drawbacks related to the use this drug. Therapeutic textiles functionalized with keratin-based particles (100% keratin; 80% keratin/20% keratin-PEG) encapsulating terbinafine were developed. The controlled release of terbinafine from the functionalized textiles was evaluated against different mimetic biologic solutions (PBS buffer-pH = 7.4, micellar solution and acidic sweat solution-pH = 4.3). The modification of keratin with polyethylene glycol (PEG) moieties favored the release of terbinafine at the end of 48 h for all the solution conditions. When the activity of functionalized textiles was tested against Trichophyton rubrum, a differentiated inhibition was observed. Textiles functionalized with 80% keratin/20% keratin-PEG encapsulating terbinafine showed a 2-fold inhibition halo compared with the textiles containing 100% keratin-encapsulating terbinafine. No activity was observed for the textiles functionalized with keratin-based particles without terbinafine. The systems herein developed revealed therapeutic potential towards nail fungal infections, taking advantage of keratin-based particles affinity to keratin structures and of the keratinase activity of T. rubrum.

Isothermal titration calorimetric assessment of lignin conversion by laccases

Lignin valorization may offer a sustainable approach to achieve a chemical industry that is not completely dependent on fossil resources for the production of aromatics. However, lignin is a recalcitrant, heterogeneous, and complex polymeric compound for which only very few catalysts can act in a predictable and reproducible manner. Laccase is one of those catalysts and has often been referred to as an ideal “green” catalyst, as it is able to oxidize various linkages within lignin to release aromatic products, with the use of molecular oxygen and formation of water as the only side product. The extent and rate of laccase‐catalyzed lignin conversion were measured using the label‐free analytical technique isothermal titration calorimetry (ITC). IITC provides the molar enthalpy of the reaction, which reflects the extent of conversion and the time‐dependent power trace, which reflects the rate of the reaction. Calorimetric assessment of the lignin conversion brought about by various fungal and bacterial laccases in the absence of mediators showed marked differences in the extent and rate of conversion for the different enzymes. Kraft lignin conversion by Trametes versicolor laccase followed Michaelis–Menten kinetics and was characterized by the following thermodynamic and kinetic parameters ΔH_ITC = −(2.06 ± 0.06)·10³ kJ mol⁻¹, K_M = 6.6 ± 1.2 μM and V_max = 0.30 ± 0.02 U/mg at 25°C and pH 6.5. We envision calorimetric techniques as important tools for the development of enzymatic lignin valorization strategies.

From Enzyme Stability to Enzymatic Bioelectrode Stabilization Processes

Bioelectrocatalysis using redox enzymes appears as a sustainable way for biosensing, electricity production, or biosynthesis of fine products. Despite advances in the knowledge of parameters that drive the efficiency of enzymatic electrocatalysis, the weak stability of bioelectrodes prevents large scale development of bioelectrocatalysis. In this review, starting from the understanding of the parameters that drive protein instability, we will discuss the main strategies available to improve all enzyme stability, including use of chemicals, protein engineering and immobilization. Considering in a second step the additional requirements for use of redox enzymes, we will evaluate how far these general strategies can be applied to bioelectrocatalysis.

Enhancement of laccase immobilization onto wet chitosan microspheres using an iterative protocol and its potential to remove micropollutants

This study was focused on creating a new and effective immobilization method for Trametes versicolor laccase (Lc) by using chitosan (CS) microspheres activated with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride. The activation of the support alternated with immobilization of the enzyme, in repetitive procedures, led to obtaining three different products. Also, the physicochemical properties of the new products were investigated and compared with those of free laccase. The discoloration and reusability properties of the immobilized Lc were evaluated using indigo carmine (IC) as a model micropollutant. The ESEM and FT-IR methods demonstrated that the Lc was successfully immobilized. The relative reaction rate and the total amount of immobilized Lc were tripled using the iterative protocol as proved by specific and Bradford assays. The maximum amount of immobilized Lc was 8.4 mg Lc/g CS corresponding to the third immobilization procedure. Compared to the free Lc, the operational stability of the immobilized Lc was significantly improved, presenting a maximum activity plateau over a pH range of 3-5 and a temperature range of 25-50 °C. The thermal inactivation study at 55 °C proved that the immobilized enzyme is three times more stable than the free Lc. The isoconversional and Michaelis-Menten methods showed that the immobilization did not affect the enzyme catalytic properties. After 32 days of storage, the residual activities are 85% for the immobilized laccase and 40% for the free one. In similar conditions, the free and immobilized Lc (2.12 x 10^-6 M) completely decolorized IC (7.15 x 10^-5 M) within 14 min. The immobilized Lc activity remained almost constant (80%) during 10 reusability cycles. All these results highlight the substantial advantages of the new immobilization protocol and demonstrate that immobilized Lc can be used as a promising micropollutant removal from real wastewater.

Laccases in Food Industry: Bioprocessing, Potential Industrial and Biotechnological Applications

Laccase is a multi-copper oxidase that catalyzes the oxidation of one electron of a wide range of phenolic compounds. The enzyme is considered eco-friendly because it requires molecular oxygen as co-substrate for the catalysis and it yields water as the sole by-product. Laccase is commonly produced by fungi but also by some bacteria, insects and plants. Due it is capable of using a wide variety of phenolic and non-phenolic substrates, laccase has potential applications in the food, pharmaceutical and environmental industries; in addition, it has been used since many years in the bleaching of paper pulp. Fungal laccases are mainly extracellular enzyme that can be recovered from the residual compost of industrial production of edible mushrooms as Agaricus bisporus and Pleurotus ostreatus. It has also been isolated from microorganisms present in wastewater. The great potential of laccase lies in its ability to oxidize lignin, one component of lignocellulosic materials, this feature can be widely exploited on the pretreatment for agro-food wastes valorization. Laccase is one of the enzymes that fits very well in the circular economy concept, this concept has more benefits over linear economy; based on "reduce-reuse-recycle" theory. Currently, biorefinery processes are booming due to the need to generate clean biofuels that do not come from oil. In that sense, laccase is capable of degrading lignocellulosic materials that serve as raw material in these processes, so the enzyme's potential is evident. This review will critically describe the production sources of laccase as by-product from food industry, bioprocessing of food industry by-products using laccase, and its application in food industry.

Substrate hydrophobicity and enzyme modifiers play a major role in the activity of lipase fromThermomyces lanuginosus

Lipase fromThermomyces lanuginosusdisplays high affinity for long-chain substrates. The chemical modification of this lipase with isothiocyanates and aldehydes was explored to broadening its specificity to chain-length differentiated substrates.

Exploring PEGylated and immobilized laccases for catechol polymerization

Laccases have been reported for their ability to eliminate hazardous phenolic compounds by oxidative polymerization. The exploitation of the oxidative behavior of different laccase forms, namely free/native, free/PEGylated, immobilized/native and immobilized/PEGylated, was assessed in this study. We found that PEGylated and immobilized laccase forms have differentiated catalytic behavior revealing distinct conversion rates and differentiated poly(catechol) chains, as confirmed by UV-Visible spectroscopy, by the total content of OH groups and by MALDI-TOF spectroscopy. The synergy underlying on the immobilized/PEGylated enzyme forms reveal to be responsible for the highest conversion rates and for the longer polymers produced.

Practical insights on enzyme stabilization

Enzymes are efficient catalysts designed by nature to work in physiological environments of living systems. The best operational conditions to access and convert substrates at the industrial level are different from nature and normally extreme. Strategies to isolate enzymes from extremophiles can redefine new operational conditions, however not always solving all industrial requirements. The stability of enzymes is therefore a key issue on the implementation of the catalysts in industrial processes which require the use of extreme environments that can undergo enzyme instability. Strategies for enzyme stabilization have been exhaustively reviewed, however they lack a practical approach. This review intends to compile and describe the most used approaches for enzyme stabilization highlighting case studies in a practical point of view.

Upgrading Laccase Production and Biochemical Properties: Strategies and Challenges

Improving laccases continues to be crucial in novel biotechnological developments and industrial applications, where they are concerned. This review breaks down and explores the potential of the strategies (conventional and modern) that can be used for laccase enhancement (increased production and upgraded biochemical properties such as stability and catalytic efficiency). The challenges faced with these approaches are briefly discussed. We also shed light on how these strategies merge and give rise to new options and advances in this field of work. Additionally, this article seeks to serve as a guide for students and academic researchers interested in laccases. This document not only gives basic information on laccases, but also provides updated information on the state of the art of various technologies that are used in this line of investigation. It also gives the readers an idea of the areas extensively studied and the areas where there is still much left to be done. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1015-1034, 2017.

Simultaneous Enhancement of Bioactivity and Stability of Laccase by Cu2+/PAA/PPEGA Matrix for Efficient Biosensing and Recyclable Decontamination of Pyrocatechol

Simultaneously enhancing the catalytic bioactivity and stability of enzyme is still an intractable issue in the enzymatic study. Herein, a facile and effective approach was designed to immobilize and modify laccase on a Cu²⁺-adsorbed pyrene-terminated block copolymer [poly(acrylic acid)/poly(poly(ethylene glycol) acrylate)] (PAA/PPEGA), which was prepared via well-controlled reversible addition-fragmentation chain transfer polymerization. PAA provided the supporting matrix for firm immobilization of Cu²⁺, an enzyme bioactivity inducer, onto the microstructure of laccase, while avoiding any contamination of the heavy metal Cu²⁺ into the following application system. The water-soluble, biocompatible, and nontoxic PPEGA was used as an ideal modifier to improve the laccase stability. Accordingly, the modified laccase exhibited enhanced catalytic bioactivity and stability simultaneously to 447% and 237%, respectively. The modified laccase was immobilized on the highly oriented pyrolytic graphite surface and large-area graphene papers through π-π stacking interactions between the pyrene moiety of PAA/PPEGA and the π-conjugated graphenelike surface. The as-prepared portable solid-state electrochemical laccase biosensor showed lowest detection limit of 50 nM (S/N ≥ 3) and long-term stability for pyrocatechol detection. Besides, the laccase immobilization on graphene paper provided efficient pyrocatechol decontamination platform with convenience and recyclability, which could retain the laccase bioactivity of 176% after 8 consecutive operations.