The β-hairpin from the Thermus thermophilus HB27 laccase works as a pH-dependent switch to regulate laccase activity

Laccase-based biocatalytic systems application in sustainable degradation of pharmaceutically active contaminants

The outflow of pharmaceutically active chemicals (PhACs) exerts a negative impact on biological systems even at extremely low concentrations. For instance, enormous threats to human and aquatic species have resulted from the widespread use of antibiotics in ecosystems, which stimulate the emergence and formation of antibiotic-resistant bacterial species and associated genes. Additionally, it is challenging to eliminate these PhACs by employing conventional physicochemical water treatment techniques. Enzymatic approaches, including laccase, have been identified as a promising alternative to eliminate a broad array of PhACs from water matrices. However, their application in environmental bioremediation is hindered by several factors, including the enzyme's stability and its location in the aqueous environment. Such obstacles may be surmounted by employing laccase immobilization, which enables enhanced stability (including inactivation caused by the substrate), and thus improved catalysis. This review emphasizes the potential hazards of PhACs to aquatic organisms within the detection concentration range of ngL-1 to µgL-1, as well as the deployment of laccase-based multifunctional biocatalytic systems for the environmentally friendly mitigation of anticancer drugs, analgesics/NSAIDs, antibiotics, antiepileptic agents, and beta blockers as micropollutants. This approach could reduce the underlying toxicological consequences. In addition, current developments, potential applications, and viewpoints have focused on computer-assisted investigations of laccase-PhACs binding at enzyme cavities and degradability prediction.

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.

Biochemical and Structural Characterization of a Novel Psychrophilic Laccase (Multicopper Oxidase) Discovered from Oenococcus oeni 229 (ENOLAB 4002)

Recently, prokaryotic laccases from lactic acid bacteria (LAB), which can degrade biogenic amines, were discovered. A laccase enzyme has been cloned from Oenococcus oeni, a very important LAB in winemaking, and it has been expressed in Escherichia coli. This enzyme has similar characteristics to those previously isolated from LAB as the ability to oxidize canonical substrates such as 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,6-dimethoxyphenol (2,6-DMP), and potassium ferrocyanide K4[Fe(CN6)], and non-conventional substrates as biogenic amines. However, it presents some distinctiveness, the most characteristic being its psychrophilic behaviour, not seen before among these enzymes. Psychrophilic enzymes capable of efficient catalysis at low temperatures are of great interest due to their potential applications in various biotechnological processes. In this study, we report the discovery and characterization of a new psychrophilic laccase, a multicopper oxidase (MCO), from the bacterium Oenococcus oeni. The psychrophilic laccase gene, designated as LcOe 229, was identified through the genomic analysis of O. oeni, a Gram-positive bacterium commonly found in wine fermentation. The gene was successfully cloned and heterologously expressed in Escherichia coli, and the recombinant enzyme was purified to homogeneity. Biochemical characterization of the psychrophilic laccase revealed its optimal activity at low temperatures, with a peak at 10 °C. To our knowledge, this is the lowest optimum temperature described so far for laccases. Furthermore, the psychrophilic laccase demonstrated remarkable stability and activity at low pH (optimum pH 2.5 for ABTS), suggesting its potential for diverse biotechnological applications. The kinetic properties of LcOe 229 were determined, revealing a high catalytic efficiency (kcat/Km) for several substrates at low temperatures. This exceptional cold adaptation of LcOe 229 indicates its potential as a biocatalyst in cold environments or applications requiring low-temperature processes. The crystal structure of the psychrophilic laccase was determined using X-ray crystallography demonstrating structural features similar to other LAB laccases, such as an extended N-terminal and an extended C-terminal end, with the latter containing a disulphide bond. Also, the structure shows two Met residues at the entrance of the T1Cu site, common in LAB laccases, which we suggest could be involved in substrate binding, thus expanding the substrate-binding pocket for laccases. A structural comparison of LcOe 229 with Antarctic laccases has not revealed specific features assigned to cold-active laccases versus mesophilic. Thus, further investigation of this psychrophilic laccase and its engineering could lead to enhanced cold-active enzymes with improved properties for future biotechnological applications. Overall, the discovery of this novel psychrophilic laccase from O. oeni expands our understanding of cold-adapted enzymes and presents new opportunities for their industrial applications in cold environments.

Bioremediation of organic pollutants by laccase-metal-organic framework composites: A review of current knowledge and future perspective

Immobilized laccases are widely used as green biocatalysts for bioremediation of phenolic pollutants and wastewater treatment. Metal-organic frameworks (MOFs) show potential application for immobilization of laccase. Their unique adsorption properties provide a synergic effect of adsorption and biodegradation. This review focuses on bioremediation of wastewater pollutants using laccase-MOF composites, and summarizes the current knowledge and future perspective of their biodegradation and the enhancement strategies of enzyme immobilization. Mechanistic strategies of preparation of laccase-MOF composites were mainly investigated via physical adsorption, chemical binding, and de novo/co-precipitation approaches. The influence of architecture of MOFs on the efficiency of immobilization and bioremediation were discussed. Moreover, as sustainable technology, the integration of laccases and MOFs into wastewater treatment processes represents a promising approach to address the challenges posed by industrial pollution. The MOF-laccase composites can be promising and reliable alternative to conventional techniques for the treatment of wastewaters containing pharmaceuticals, dyes, and phenolic compounds. The detailed exploration of various immobilization techniques and the influence of MOF architecture on performance provides valuable insights for optimizing these composites, paving the way for future advancements in environmental biotechnology. The findings of this research have the potential to influence industrial wastewater treatment and promoting cleaner treatment processes and contributing to sustainability efforts.