Boosted activity by engineering the enzyme microenvironment in cascade reaction: A molecular understanding

Chitosan-gallic acid conjugate with enhanced functional properties and synergistic wound healing effect

Chitosan-gallic acid conjugates were synthesized by carbodiimide method and characterized by physicochemical methods (UV-vis, FTIR, 1H NMR, TGA). The FTIR and NMR assays confirmed that the chemical interaction occurred solely due to the formation of an amide bond. It was established that by varying the ratio of the components during synthesis it is possible to obtain conjugates with desired conjugation ratio, grafting efficiency and gallic acid content up to 8.09 ± 1.72 %, 70.51 ± 9.45 % and 79.9 ± 2.4 μg gallic acid/mg chitosan, respectively. Chitosan-gallic acid conjugate with a 5 % conjugation ratio demonstrated excellent antioxidant properties: the IC50 value for ABTS radical scavenging activity was 0.0073 ± 0.0001 mg/mL. In vitro tests showed that conjugation of chitosan with gallic acid provided the antiglycemic activity of the material and its good biocompatibility. A low level of cytotoxicity was recorded in the HaCaT cell line model (IC50 was 1030.4 μg/mL). The received eco-friendly chitosan-gallic acid conjugate effectively inhibited the growth of thermophilic spore-forming bacteria G. thermodenitrificans and the resistant to classical antibiotics strain A. palidus. The results of an in vivo comparative analysis showed that chitosan-gallic acid conjugate had excellent wound healing properties due to the synergism of the polysaccharide and the natural antioxidant.

Optimization of D-amino acid oxidase and epoxide hydrolase through high-performance characterization for targeted cancer therapy in sustainable biocatalysis

Enzymes with great stability, specificity, and efficiency are essential for sustainable biocatalysis. D-amino acid oxidase (DAAO) and Epoxide hydrolase (EH) have special catalytic capabilities in green chemistry with minimum structural and functional limitations. An improved framework has been proposed which uses enzyme characterization methods for High-Performance Rare Enzyme Characterization and Evolution System (H-PRECES) for targeted cancer therapy. Under physiological environments, this study multiplied EH stability by three and DAAO activity by seven using a mix of directed evolution and high-throughput screening. Molecular docking indicated an affinity score of -2.466 kcal/mol of DAAO with d-serine, -2.372 kcal/mol of DAAO with D-alanine, and - 4.482 kcal/mol of EH with styrene oxide. In model systems, the improved enzymes also showed a considerable decrease in reaction time and an increase of 25 % in substrate specificity. The research aimed to improve the biostability and catalytic efficiency of epoxide hydrolase (EH) and D-amino acid oxidase (DAAO) for specific anticancer uses. Specific results, such as a 2.8-fold enhancement in catalytic efficiency (kcat/Km), a 6.7 °C increase in thermal stability (Tm), and improved substrate selectivity verified by docking and kinetic studies. Cytotoxicity assays further confirmed selective tumor cell inhibition with over 70 % cell viability retention in normal cells. Future research should focus on developing specific delivery methods to improve therapeutic accuracy and enzyme stability under physiological circumstances.

Altering the Properties of Laccases from Ensifer meliloti (Sinorhizobium meliloti) and Cerrena unicolor by Chemical Modifications of Proteins

Due to their catalytic performance, laccases constitute one of the most promising groups of enzymes for potential applications in modern biotechnology. In this study, we aimed to chemically modify Ensifer meliloti (Sinorhizobium meliloti) and Cerrena unicolor laccase and comparatively characterize the structures of both enzymes. The most characteristic feature was the spatial localization of lysine residues, predominantly positioned distal to the active site region for both compared enzymes. The solvent-accessible surface area (SASA) analysis showed that bacterial laccase was characterized by a larger hydrophobic SASA than the fungal enzyme. The pKa prediction identified only one Lys in the E. meliloti laccase structure susceptible to modification. Modifications were achieved by using mono- and bifunctional crosslinking agents, and glycosylations were also performed. The degree of protein modification ranged from 0% for glucose- and galactose-modified E. meliloti laccase and citraconic anhydride-modified (CA) C. unicolor laccase to 62.94% for the palmitic acid N-hydroxysuccinimide ester-modified E. meliloti enzyme. The stability of covalently modified laccases over a wide pH and temperature ranges and in the presence of inhibitors was investigated. Protein modifications with polymeric sucrose (PS) and ethylene glycol bis-(succinimidyl succinate) (EGNHS) significantly increased the activity of the bacterial and fungal laccases by 15 and 19%, respectively. Although pH optima remained relatively unchanged by modifications, certain variants, especially CA-modified bacterial protein and EGNHS-modified C. unicolor enzyme, exhibited improved stability at near-neutral pH (6-7). Modification of the bacterial enzyme with glutaraldehyde-carbodiimide (GA-CDI-ver) and of the fungal enzyme with CA was the most effective in improving its thermal stability. Chemical modifications using GA, CDI, GA-CDI, and PS allowed E. meliloti L 3.8 laccase to retain full activity in the presence of 5 mM NaI, whereas CA-, PS-, and EGNHS-modified C. unicolor variants retained their activity even at elevated NaCl concentrations. The results clearly demonstrate that the outcome of chemical modifications is closely linked to enzyme-specific structural features and that selecting an appropriate modification strategy is critical to achieving the desired effect.

Engineered polymer nanoparticles as artificial chaperones facilitating the selective refolding of denatured enzymes

Molecular chaperones assist in protein refolding by selectively binding to proteins in their nonnative states. Despite progress in creating artificial chaperones, these designs often have a limited range of substrates they can work with. In this paper, we present molecularly imprinted flexible polymer nanoparticles (nanoMIPs) designed as customizable biomimetic chaperones. We used model proteins such as cytochrome c, laccase, and lipase to screen polymeric monomers and identify the most effective formulations, offering tunable charge and hydrophobic properties. Utilizing a dispersed phase imprinting approach, we employed magnetic beads modified with destabilized whole-protein as solid-phase templates. This process involves medium exchange facilitated by magnetic pulldowns, resulting in the synthesis of nanoMIPs featuring imprinted sites that effectively mimic chaperone cavities. These nanoMIPs were able to selectively refold denatured enzymes, achieving up to 86.7% recovery of their activity, significantly outperforming control samples. Mechanistic studies confirmed that nanoMIPs preferentially bind denatured rather than native enzymes, mimicking natural chaperone interactions. Multifaceted analyses support the functionality of nanoMIPs, which emulate the protective roles of chaperones by selectively engaging with denatured proteins to inhibit aggregation and facilitate refolding. This approach shows promise for widespread use in protein recovery within biocatalysis and biomedicine.

Recent advances in microbial and enzymatic engineering for the biodegradation of micro- and nanoplastics

This review examines the escalating issue of plastic pollution, specifically highlighting the detrimental effects on the environment and human health caused by microplastics and nanoplastics. The extensive use of synthetic polymers such as polyethylene (PE), polyethylene terephthalate (PET), and polystyrene (PS) has raised significant environmental concerns because of their long-lasting and non-degradable characteristics. This review delves into the role of enzymatic and microbial strategies in breaking down these polymers, showcasing recent advancements in the field. The intricacies of enzymatic degradation are thoroughly examined, including the effectiveness of enzymes such as PETase and MHETase, as well as the contribution of microbial pathways in breaking down resilient polymers into more benign substances. The paper also discusses the impact of chemical composition on plastic degradation kinetics and emphasizes the need for an approach to managing the environmental impact of synthetic polymers. The review highlights the significance of comprehending the physical characteristics and long-term impacts of micro- and nanoplastics in different ecosystems. Furthermore, it points out the environmental and health consequences of these contaminants, such as their ability to cause cancer and interfere with the endocrine system. The paper emphasizes the need for advanced analytical methods and effective strategies for enzymatic degradation, as well as continued research and development in this area. This review highlights the crucial role of enzymatic and microbial strategies in addressing plastic pollution and proposes methods to create effective and environmentally friendly solutions.

Identification of a novel thermostable transaminase and its application in L-phosphinothricin biosynthesis

Transaminase (TA) is a crucial biocatalyst for enantioselective production of the herbicide L-phosphinothricin (L-PPT). The use of enzymatic cascades has been shown to effectively overcome the unfavorable thermodynamic equilibrium of TA-catalyzed transamination reaction, also increasing demand for TA stability. In this work, a novel thermostable transaminase (PtTA) from Pseudomonas thermotolerans was mined and characterized. The PtTA showed a high specific activity (28.63 U/mg) towards 2-oxo-4-[(hydroxy)(methyl)phosphinoyl]butyric acid (PPO), with excellent thermostability and substrate tolerance. Two cascade systems driven by PtTA were developed for L-PPT biosynthesis, including asymmetric synthesis of L-PPT from PPO and deracemization of D, L-PPT. For the asymmetric synthesis of L-PPT from PPO, a three-enzyme cascade was constructed as a recombinant Escherichia coli (E. coli G), by co-expressing PtTA, glutamate dehydrogenase (GluDH) and D-glucose dehydrogenase (GDH). Complete conversion of 400 mM PPO was achieved using only 40 mM amino donor L-glutamate. Furthermore, by coupling D-amino acid aminotransferase (Ym DAAT) from Bacillus sp. YM-1 and PtTA, a two-transaminase cascade was developed for the one-pot deracemization of D, L-PPT. Under the highest reported substrate concentration (800 mM D, L-PPT), a 90.43% L-PPT yield was realized. The superior catalytic performance of the PtTA-driven cascade demonstrated that the thermodynamic limitation was overcome, highlighting its application prospect for L-PPT biosynthesis. KEY POINTS: • A novel thermostable transaminase was mined for L-phosphinothricin biosynthesis. • The asymmetric synthesis of L-phosphinothricin was achieved via a three-enzyme cascade. • Development of a two-transaminase cascade for D, L-phosphinothricin deracemization.

Chemical modification of enzymes to improve biocatalytic performance

Improvement in intrinsic enzymatic features is in many instances a prerequisite for the scalable applicability of many industrially important biocatalysts. To this end, various strategies of chemical modification of enzymes are maturing and now considered as a distinct way to improve biocatalytic properties. Traditional chemical modification methods utilize reactivities of amine, carboxylic, thiol and other side chains originating from canonical amino acids. On the other hand, noncanonical amino acid- mediated 'click' (bioorthogoal) chemistry and dehydroalanine (Dha)-mediated modifications have emerged as an alternate and promising ways to modify enzymes for functional enhancement. This review discusses the applications of various chemical modification tools that have been directed towards the improvement of functional properties and/or stability of diverse array of biocatalysts.