Rapid identification of fungal laccases/oxidases with different pH-optimum

Lysine enhances the photoresponsive oxidase-like activity of twin Cd0.7Zn0.3S for direct colorimetric detection of lysine

BACKGROUND

Lysine (Lys) is one of the eight essential amino acids for the human body, which can't be synthesized by the body and must be obtained from external sources. And the detection of Lys is of significance for disease monitoring. The construction of photoresponsive nanozymes based analytical methods have received increasing attention and have been successfully achieved for the detection of metal ions, small molecules and natural enzymes. However, the exploration of photoresponsive nanozyme in amino acids detection has not been tapped.

RESULTS

This study presents an innovative method based on surface passivation by Lys to stimulate the photoresponsive nanozyme activity of twin Cd0.7Zn0.3S nanomaterials. Specifically, Lys can bind with twin Cd0.7Zn0.3S, which filled the dangling bonds on the surface of Cd0.7Zn0.3S and caused passivation of the surface state, resulting in the promotion of the separation efficiency of electrons and holes, along with the facilitation of the production of active intermediates. Therefore, the Cd0.7Zn0.3S in the presence of Lys showed a high catalytic oxidation ability for the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to oxidized TMB (oxTMB). This new kind of photoresponsive oxidase-like activity could be regulated by switching visible light sources and showed the specificity of being only affected by Lys without influenced by other amino acids, thus achieved direct colorimetric detection of Lys. The linear range for Lys detection was 1-100 μM, with a detection limit of 0.18 μM (S/N = 3).

SIGNIFICANCE

This study developed a new nanozyme of twin Cd0.7Zn0.3S, whose activity leverages on Lys as a stimulator. Moreover, the Lys detection method proposed by us had the characteristics of high sensitivity, good selectivity, fast detection speed, and low cost. Therefore, it holds significant potential application value, making it a promising candidate in the field of Lys detection and related research areas.

Enzymatic Treatment of Lignin in Alkaline Homogeneous Systems: A Review on Alkaliphilic Laccases

This short review explores the enzymatic treatment of lignin in alkaline homogeneous systems, focusing on alkaliphilic laccases. In acidic conditions, native laccases are known to promote lignin polymerization, while the addition of mediators enables depolymerization into valuable small molecules. Alkaliphilic laccases, which remain active in basic pH where the vast majority of industrial lignins are soluble, present an interesting alternative. However, the literature shows varied outcomes - polymerization, depolymerization, or both processes - making it difficult to draw clear trends. This review aims to summarize the current state of the art of the enzymatic treatment of lignin in alkaline conditions.

Proteomic characterization of Pseudogymnoascus spp. isolates from polar and temperate regions

Proteomics has been used extensively in the field of mycology, mainly in trying to understand the complex network of protein-protein interactions that has been implicated in the molecular functions of fungi. It is also a useful tool to compare metabolic differences within a genus. Species of Pseudogymnoascus, a genus under the phyla Ascomycota, have been shown to play an important role in the soil environment. They have been found in both polar and temperate regions and are a known producer of many extracellular hydrolases that contribute to soil decomposition. Despite the apparent importance of Pseudogymnoascus spp. in the soil ecosystem, investigations into their molecular functions are still very limited. In the present study, proteomic characterization of six Pseudogymnoascus spp. isolated from three biogeographic regions (the Arctic, Antarctic, and temperate regions) was carried out using tandem mass spectrometry. Prior to proteomic analysis, the optimization for protein extraction was carried out. Trichloroacetic acid‑acetone‑phenol was found to be the best extraction method to be used for proteomic profiling of Pseudogymnoascus spp. The proteomic analysis identified 2003 proteins that were successfully mapped to the UniProtKB database. The identified proteins were clustered according to their biological processes and molecular functions. The shared proteins found in all Pseudogymnoascus spp. (1201 proteins) showed a significantly close relationship in their basic cellular functions, despite differences in morphological structures. Analysis of Pseudogymnoascus spp. proteome also identified proteins that were unique to each region. However, a high number of these proteins belonged to protein families of similar molecular functions, namely, transferases and hydrolases. Our proteomic data can be used as a reference for Pseudogymnoascus spp. across different global regions and a foundation for future soil ecosystem function research.

Unusual Oligomeric Laccase-like Oxidases from Ascomycete Curvularia geniculata VKM F-3561 Polymerizing Phenylpropanoids and Phenolic Compounds under Neutral Environmental Conditions

The unique oligomeric alkaliphilic laccase-like oxidases of the ascomycete C. geniculata VKM F-3561 (with molecular masses about 1035 and 870 kDa) were purified and characterized for the first time. The ability of the enzymes to oxidize phenylpropanoids and phenolic compounds under neutral environmental conditions with the formation of previously unknown di-, tri-, and tetrameric products of transformation was shown. The possibility to obtain industrially valuable compounds (dihydroxybenzyl alcohol and hydroxytyrosol) from caffeic acid using laccase-like oxidases of C. geniculata VKM F-3561 has been shown. Complete nucleotide sequence of the laccase gene, which is expressed at the peak of alkaliphilic laccase activity of the fungus, and its promoter region were determined. Based on the phylogenetic analysis of the nucleotide sequence, the nearest relationship of the isolated laccase gene with similar genes of fungi of the genera Alternaria, Bipolaris, and Cochliobolus was shown. Homologous model of the laccase structure was predicted and a proton channel was found, which was presumably responsible for the accumulation and transport of protons to T2/T3-copper center in the alkaliphilic laccase molecule and providing the functional activity of the enzyme in the neutral alkaline environment conditions.

The Laccase of Myrothecium roridum VKM F-3565: A New Look at Fungal Laccase Tolerance to Neutral and Alkaline Conditions

Most of the currently known fungal laccases show their maximum activity under acidic environmental conditions. It is known that a decrease in the activity of a typical laccase at neutral or alkaline pH values is the result of an increase in the binding of the hydroxide anion to the T2/T3 copper center, which prevents the transfer of an electron from the T1 Cu to the trinuclear copper center. However, evolutionary pressure has resolved the existing limitations in the catalytic mechanism of laccase, allowing such enzymes to be functionally active under neutral/alkaline pH conditions, thereby giving fungi an advantage for their survival. Combined molecular and biochemical studies, homological modeling, calculation of the electrostatic potential on the Connolly surface at pH 5.0 and 7.0, and structural analysis of the novel alkaliphilic laccase of Myrothecium roridum VKM F-3565 and alkaliphilic and acidophilic fungal laccases with a known structure allowed a new intramolecular channel near the one of the catalytic aspartate residues at T2-copper atom to be found. The amino acid residues of alkaliphilic laccases forming this channel can presumably serve as proton donors for catalytic aspartates under neutral conditions, thus ensuring proper functioning. For the first time for ascomycetous laccases, the production of new trimeric products of phenylpropanoid condensation under neutral conditions has been shown, which could have a potential for use in pharmacology.

Protein homeostasis, regulation of energy production and activation of DNA damage-repair pathways are involved in the heat stress response of Pseudogymnoascus spp

Proteome changes can be used as an instrument to measure the effects of climate change, predict the possible future state of an ecosystem and the direction in which is headed. In this study, proteomic and GO functional enrichment analysis of six Pseudogymnoascus spp. isolated from various global biogeographical regions were carried out to determine their response to heat stress. In total, 2,122 proteins were identified with high confidence. Comparative quantitative analysis showed that changes in proteome profiles varied greatly between isolates from different biogeographical regions. Although the identities of the proteins that changed varied between the different regions, the functions they governed were similar. Gene Ontology analysis showed enrichment of proteins involved in multiple protective mechanisms, including the modulation of protein homeostasis, regulation of energy production, and activation of DNA damage and repair pathways. Our proteomic analysis did not show any clear relationship between protein changes and the strains' biogeographical origins. This article is protected by copyright. All rights reserved.

Laccase and horseradish peroxidase for green treatment of phenolic micropollutants in real drinking water and wastewater

Biologically active micropollutants that contain diverse phenolic/aromatic structures are regularly present in wastewater effluents and are even found in drinking water. Advanced green technologies utilizing immobilized laccase and/or peroxidase, which target these micropollutants directly, may provide a reasonable alternative to standard treatments. Nevertheless, the use of these enzymes is associated with several issues that may prevent their application, such as the low activity of laccase at neutral and basic pH or the necessity of hydrogen peroxide addition as a co-substrate for peroxidases. In this study, the activity of laccase from Trametes versicolor and horseradish peroxidase was evaluated across a range of commonly used substrates (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), syringaldazine, and guaiacol). Moreover, conditions for their optimal performance were explored along with an assessment of whether these conditions accurately reflect the effectivity of both enzymes in the degradation of a mixture of bisphenol A, 17α-ethinylestradiol, triclosan, and diclofenac in tap drinking water and secondary wastewater effluent. Laccase and horseradish peroxidase showed optimal activity at strongly acidic pH if ABTS was used as a substrate. Correspondingly, the activities of both enzymes detected using ABTS in real waters were significantly enhanced by adding approximately 2.5% (v/v) of McIlvaine's buffer. Degradation of a mixture of micropollutants in wastewater with 2.5% McIlvaine's buffer (pH 7) resulted in a substantial decrease in estrogenic activity. Low degradation efficiency of micropollutants by laccase was observed in pure McIlvaine's buffer of pH 3 and 7, compared with efficient degradation in tap water of pH 7.5 without buffer. This study clearly shows that enzyme activity needs to be evaluated on micropollutants in real waters as the assessment of optimal conditions based on commonly used substrates in pure buffer or deionized water can be misleading.

Enzymatic Electroanalytical Biosensor Based on Maramiellus colocasiae Fungus for Detection of Phytomarkers in Infusions and Green Tea Kombucha

In this work, we developed an enzymatic voltammetric biosensor for the determination of catechin and gallic acid in green tea and kombucha samples. The differential pulse voltammetry (DPV) methodology was optimized regarding the amount of crude enzyme extract, incubation time in the presence of the substrates, optimal pH, reuse of the biosensor, and storage time. Samples of green tea and kombucha were purchased in local markets in the city of Goiânia-GO, Brazil. High performance liquid chromatography (HPLC) and Folin-Ciocalteu spectrophotometric techniques were performed for the comparison of the analytical methods employed. In addition, two calibration curves were made, one for catechin with a linear range from 1 to 60 µM (I = −0.152 * (catechin) − 1.846), with a detection limit of 0.12 µM and a quantification limit of 0.38 µM and one for gallic acid with a linear range from 3 to 60 µM (I = −0.0415 * (gallic acid) − 0.0572), with a detection limit of 0.14 µM and a quantification limit of 0.42 µM. The proposed biosensor was efficient in the determination of phenolic compounds in green tea.

Multicopper oxidase (MCO) laccase from Stropharia sp. ITCC-8422: an apparent authentication using integrated experimental and in silico analysis

In the present study, specificity of laccase from Stropharia sp. ITCC-8422 against various substrates, i.e. 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 2,6-dimethoxyphenol (DMP), guaiacol (GCL) and syringaldazine (SYZ) was determined. It exhibited maximum affinity against ABTS, followed by DMP and negligible activity for GCL and SYZ. As the concentration of substrate increased from 0.5 to 1.5 mM (ABTS) and 1 to 5 mM (DMP), the activity increased from 301.1 to 567.8 U/L and 254.4 to 436.2 U/L. Further, quadrupole time-of-flight liquid chromatography mass spectrometry (QTOF-LCMS) analysis of the extracellular proteome of Stropharia sp. ITCC-8422 identified eighty-four (84) extracellular proteins. The peptide sequence for the enzyme of interest exhibited sequence similarity with laccase-5 of Trametes pubescens. Using high molecular mass sequence of laccase-5, the protein structure of laccase was modelled and binding energy of laccase with four substrates, i.e. ABTS (- 5.65), DMP (- 4.65), GCL (- 4.66) and SYZ (- 5.5) was determined using autodock tool. The experimental and in silico analyses revealed maximum activity of laccase and lowest binding energy with ABTS. Besides, laccase was purified and it exhibited 2.1-fold purification with purification yield of 20.4% and had stability of 70% at pH 5-9 and 30-40 ℃. In addition, the bioremediation potential of laccase was explored by in silico analysis, where the binding energy of laccase with alizarin cyanine green was - 6.37 and both in silico work and experimental work were in agreement.