Enzyme Activity Measurements Research Articles

Synergistic detoxification efficiency and mechanism of triclocarban degradation by a bacterial consortium in the liver-gut-microbiota axis of zebrafish (Danio rerio)

Triclocarban (TCC), an emerging organic contaminant, poses a potential threat to human health with long-term exposure. Here, Rhodococcus rhodochrous BX2 and Pseudomonas sp. LY-1 were utilized to degrade TCC at environmental related concentrations for enhancing TCC biodegradation and investigating whether the toxicity of intermediate metabolites is lower than that of the parent compound. The results demonstrated that the bacterial consortium could degrade TCC by 82.0% within 7 days. The calculated 96 h LC50 for TCC, as well as its main degradation product 3,4-Dichloroaniline (DCA) were 0.134 mg/L and 1.318 mg/L respectively. Biodegradation also alleviated histopathological lesions induced by TCC in zebrafish liver and gut tissues. Liver transcriptome analysis revealed that biodegradation weakened differential expression of genes involved in disrupted immune regulation and lipid metabolism caused by TCC, verified through RT-qPCR analysis and measurement of related enzyme activities and protein contents. 16 S rRNA sequencing indicated that exposure to TCC led to gut microbial dysbiosis, which was efficiently improved through TCC biodegradation, resulting in decreased relative abundances of major pathogens. Overall, this study evaluated potential environmental risks associated with biodegradation of TCC and explored possible biodetoxification mechanisms, providing a theoretical foundation for efficient and harmless bioremediation of environmental pollutants.

Decoupling between the genetic potential and the metabolic regulation and expression in microbial organic matter cleavage across microbiomes.

Omics tools are used to explore adaptive mechanism of microbes in diverse systems, but the advantages and limitations of different omics tools remain skeptical. Here, we reported distinct profiles in microbial secretory enzyme composition revealed by different omics methods. In general, the predicted function from metagenomic analysis decoupled from the expression of corresponding transcripts/proteins. Linking omics results to taxonomic origin, functional capability, substrate specificity, secretion preference, and enzymatic activity measurement suggested the substrate's source, concentration and stoichiometry impose strong filtering on the expression of extracellular enzymes, which may overwrite the genetic potentials. Our results present an integrated perspective on the need for multi-dimensional characterization of microbial adaptation in a changing environment.

Studies on α-amylase inhibition by acarbose and quercetin using fluorescence, circular dichroism, docking, and dynamics simulations

This study looked at the effects of acarbose (ACA) and quercetin (QUE) on α-amylase activity, employing QUE and ACA to measure enzyme activity. The study observed that both drugs suppressed α-amylase activity, with greater inhibition reported at higher concentrations. The use of tryptophan residues as an intrinsic fluorescence probe permitted the observation of conformational changes in α-amylase, with CD measurements utilized to explore the secondary structure in the presence of QUE and ACA. Docking studies revealed an effective interaction between α-amylase, quercetin and acarbose, with a higher binding energy. Finally, a trajectory analysis was done to establish the stability and volatility of these complexes. These findings have potential significance for the development of new α-amylase-related therapeutics.

Genotype-biochemical phenotype analysis in newborns with biotinidase deficiency in Southeastern Anatolia

ObjectiveBiotinidase deficiency (BTD) is characterized by a wide range of genetic variants. However, the correlation between these variants and the biochemical phenotypes of BTD is not well-established due to the diversity of the BTD gene, the variable nature of biotinidase, and difficulties in measuring enzyme activity. This study aims to identify BTD gene variants in newborns screened for biotinidase deficiency in Southeastern Anatolia and to examine the correlation between these variants and biochemical phenotypes.Materials and methodsBTD variant analysis and biotinidase enzyme (BT) activity measurements were performed on 711 newborns. Enzyme activity was measured using the colorimetric method. Biochemical phenotyping was categorized into three groups based on mean residual enzyme activity: profound (≤ 10%), partial (10.1–30%), and normal (> 30.1%). The pathogenicity of BTD gene variants was determined using BTD databases.ResultsThe biochemical phenotypes were distributed as follows: a) profound: n = 22 (3%), b) partial: n = 95 (13.3%), and c) normal: n = 594 (83.7%). The mean enzyme activities (%) for these groups were 8.79 ± 1.87, 22.67 ± 4.55, and 97.98 ± 17.45, respectively. The most common alleles and their frequencies were p.D444H (n = 526) (37%), p.R157H (n = 172) (12.1%), and p.C33Ffster*36 (n = 73) (9%). The pathogenicity of the variants was as follows: pathogenic: 481 (33.8%), likely pathogenic: 4 (0.2%), and variant of uncertain significance (VUS): 538 (37.8%).ConclusionIn this large cohort in Southeastern Anatolia, the most common alleles were p.D444H, p.R157H, and p.C33Ffster*36 in BTD variants. The results indicate a low concordance between the biochemical phenotype and genotype in newborns with BTD. This study highlights the inadequacy of predicting the biochemical phenotype based solely on variant pathogenicity in biotinidase deficiency during the neonatal period.

Dietary antarctic krill improves antioxidant capacity, immunity and reduces lipid accumulation, insights from physiological and transcriptomic analysis of Plectropomus leopardus

BackgroundDue to its enormous biomass, Antarctic krill (Euphausia superba) plays a crucial role in the Antarctic Ocean ecosystem. In recent years, Antarctic krill has found extensive application in aquaculture, emerging as a sustainable source of aquafeed with ideal nutritional profiles. However, a comprehensive study focused on the detailed effects of dietary Antarctic krill on aquaculture animals, especially farmed marine fishes, is yet to be demonstrated.ResultsIn this study, a comparative experiment was performed using juvenile P. leopardus, fed with diets supplemented with Antarctic krill (the krill group) or without Antarctic krill (the control group). Histological observation revealed that dietary Antarctic krill could reduce lipid accumulation in the liver while the intestine exhibited no obvious changes. Enzyme activity measurements demonstrated that dietary Antarctic krill had an inhibitory effect on oxidative stress in both the intestine and the liver. By comparative transcriptome analysis, a total of 1,597 and 1,161 differentially expressed genes (DEGs) were identified in the intestine and liver, respectively. Functional analysis of the DEGs showed multiple enriched terms significantly related to cholesterol metabolism, antioxidants, and immunity. Furthermore, the expression profiles of representative DEGs, such as dhcr7, apoa4, sc5d, and scarf1, were validated by qRT-PCR and fluorescence in situ hybridization. Finally, a comparative transcriptome analysis was performed to demonstrate the biased effects of dietary Antarctic krill and astaxanthin on the liver of P. leopardus.ConclusionsOur study demonstrated that dietary Antarctic krill could reduce lipid accumulation in the liver of P. leopardus, enhance antioxidant capacities in both the intestine and liver, and exhibit molecular-level improvements in lipid metabolism, immunity, and antioxidants. It will contribute to understanding the protective effects of Antarctic krill in P. leopardus and provide insights into aquaculture nutritional strategies.

FRET Sensor-Modified Synthetic Hydrogels for Real-Time Monitoring of Cell-Derived Matrix Metalloproteinase Activity using Fluorescence Lifetime Imaging.

Matrix remodeling plays central roles in a range of physiological and pathological processes and is driven predominantly by the activity of matrix metalloproteinases (MMPs), which degrade extracellular matrix (ECM) proteins. Our understanding of how MMPs regulate cell and tissue dynamics is often incomplete as in vivo approaches are lacking and many in vitro strategies cannot provide high-resolution, quantitative measures of enzyme activity in situ within tissue-like 3D microenvironments. Here, we incorporate a Förster resonance energy transfer (FRET) sensor of MMP activity into fully synthetic hydrogels that mimic many properties of the native ECM. We then use fluorescence lifetime imaging to provide a real-time, fluorophore concentration-independent quantification of MMP activity, establishing a highly accurate, readily adaptable platform for studying MMP dynamics in situ. MCF7 human breast cancer cells encapsulated within hydrogels highlight the detection of MMP activity both locally, at the sub-micron level, and within the bulk hydrogel. Our versatile platform may find use in a range of biological studies to explore questions in the dynamics of cancer metastasis, development, and tissue repair by providing high-resolution, quantitative and in situ readouts of local MMP activity within native tissue-like environments.

Measurement of the intracellular active metabolites of thiopurine drugs to evaluate the enzymatic activity of nudix hydrolase 15 in human blood samples

Thiopurine is metabolized to 6-thio-(deoxy) guanosine triphosphate (6-thio-(d) GTP), which is then incorporated into DNA or RNA and causes cytotoxicity. Nudix hydrolase 15 (NUDT15) reduces the cytotoxic effects of thiopurine by converting 6-thio-(d) GTP to 6-thio-(d) guanosine monophosphate (6-thio-(d) GMP). NUDT15 polymorphisms like the Arg139Cys variant are strongly linked to thiopurine-induced severe leukocytopenia and alopecia. Therefore, measurement of NUDT15 enzymatic activity in individual patients can help predict thiopurine tolerability and adjust the dosage. We aimed to develop a quantitative assay for NUDT15 enzymatic activity in human blood samples. Blood samples were collected from donors whose NUDT15 genetic status was determined. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to assess the 6-thio-GTP metabolic activity in cell extracts. Because 6-thio-guanosine diphosphate (6-thio-GDP) and 6-thio-GMP were generated upon incubation of 6-thio-GTP with human blood cell extracts, the method detecting 6-thio-GTP, 6-thio-GDP, and 6-thio-GMP was validated. All three metabolites were linearly detected, and the lower limit of quantification (LLOQ) of 6-thio-GTP, 6-thio-GDP, and 6-thio-GMP were 5 μM, 1 μM, and 2 μM, respectively. Matrix effects of human blood cell extracts to detect 6-thio-GTP, 6-thio-GDP, and 6-thio-GMP were 99.0 %, 100.5 %, and 101.4 %, respectively, relative to the signals in the absence of blood cell extracts. The accuracy and precision of the method and the stability of the samples were also assessed. Using this established method, the genotype-dependent differences in NUDT15 activities were successfully determined using cell extracts derived from human blood cells with NUDT15 wild-type (WT) or Arg139Cys variant and 6-thio-GTP (100 μM) as a substrate (18.1, 14.9, and 6.43 μM/h/106 cells for WT, Arg139Cys heterozygous, and homozygous variant, respectively). We developed a method for quantifying intracellular NUDT15 activity in peripheral blood mononuclear cells (PBMCs), which we defined as the conversion of 6-thio-GTP to 6-thio-GMP. Although PBMCs preparation takes some time, its reproducibility in experiments makes it a promising candidate for clinical application. This method can tell the difference between WT and Arg139Cys homozygous blood samples. Even in patients with WT NUDT15, WT samples showed variations in NUDT15 activity, which may correlate with variations in thiopurine dosage.

Measuring Phosphoglycolate Phosphatase Activity Using NMR Detection of Glycolate.

Besides the historical and traditional use of nuclear magnetic resonance (NMR) spectroscopy as a structure elucidation tool for proteins and metabolites, its quantification ability allows the determination of metabolite amounts and therefore enzymatic activity measurements. For this purpose, 1H-NMR with adapted water pulse pre-saturation sequences and calibration curves with commercial standard solutions can be used to quantify the photorespiratory cycle intermediates, 2-phosphoglycolate and glycolate, associated with the phosphoglycolate phosphatase reaction. The intensity of the 1H-NMR signal of glycolate produced by the activity of purified recombinant Arabidopsis thaliana PGLP1 can therefore be used to determine PGLP1 enzymatic activities and kinetic parameters.

Measurement of Photorespiratory Cycle Enzyme Activities in Leaves Exposed to Abiotic Stress.

Photorespiration, an essential metabolic component, is a classic example of interactions between the intracellular compartments of a plant cell: the chloroplast, peroxisome, mitochondria, and cytoplasm. The photorespiratory pathway is often modulated by abiotic stress and is considered an adaptive response. Monitoring the patterns of key enzymes located in different subcellular components would be an ideal approach to assessing the modulation of the photorespiratory metabolism under abiotic stress. This chapter describes the procedures for assaying several individual enzyme activities of key photorespiratory enzymes and evaluating their response to oxidative/photooxidative stress. It is essential to ascertain the presence of stress in the experimental material. Therefore, procedures for typical abiotic stress induction in leaves by highlighting without or with menadione (an oxidant that targets mitochondria) are also included.

Measurement of enzyme activity of insoluble substrates based on ordered porous layer interferometry and the application in evaluation of thrombolytic drugs.

The development of innovative methods for real-time surveillance of enzymatic activity determination processes is essential, particularly for insoluble substrate enzymatic assessments. In this work, a novel method for enzymatic activity determination was devised by assembling a 190 nm silica colloidal crystal (SCC) film onto a glass slide, coupled with Ordered Porous Layer Interferometry (OPLI) technology. By fixing the substrate of the enzyme on the surface of the silica sphere, a solid-liquid interface can be formed for monitoring enzymatic activity. The enzymatic activity is gauged by the change in the SCC film's thickness caused by the digestion of the loaded substrate. The procedure of chymotrypsin-mediated casein digestion was documented in real time, facilitating the examination of chymotrypsin's activity and kinetics. The newly-developed enzymatic activity determination method demonstrated exceptional sensitivity towards chymotrypsin activity, with a linear range spanning 0.0505-2.02 units per mg. Additionally, the method was extended to the assessment of fibrinolysis enzyme activity and kinetic analysis, yielding promising results. Therefore, this technique can serve as a real-time, user-friendly, cost-effective novel approach for enzymatic activity determination, providing fresh perspectives for enzymatic activity determination studies.

Prevalence of Glucose-6-Phosphate Dehydrogenase deficiency among Hausa and Fulani ethnics in Kano, North-West Nigeria

Background: Glucose-6-phosphate dehydrogenase catalyzes the rate-determining step in the pentose phosphate pathway. Its activity is a key determinant of the reduced nicotinamide adenine dinucleotide phosphate to oxidized nicotinamide adenine dinucleotide phosphate (NADPH-to-NADP+) ratio in the cytoplasm and thus contributes to the replenishment of the antioxidant glutathione system. Glucose-6-phosphate dehydrogenase deficiency is a common X-linked human enzyme defect of red blood cells. Individuals with this gene defect appear normal until exposed to oxidative stress which induces haemolysis but it is infrequently taken into consideration in health practices. Aim: The present work was designed to determine the frequency of occurrence of glucose-6-phosphate dehydrogenase (G-6-PD) deficiency among Hausa and Fulani ethnics. Material and methods: Cross-sectional comparative study in which 5 mL of venous blood samples were collected from 1000 individuals (596 males and 404 females) all of whom gave informed consent were screened for G-6-PD-deficiency by qualitative methaemoglobin reduction and quantitative enzyme activity measurement techniques. Results: Glucose-6-phoshate dehydrogenase deficiency was found in 194 (19.4%) of participants studied. Of these 10.3% were Fulani and 22.2% were Hausa with mean G-6-PD enzyme activity of 2.5 IU/gHb in a range from 1.4 to 2.4 IU/gHb. G-6-PD deficiency was found in 121 of 596 (20.3%) males and 73 of 404 (18.1%) females screened. Conclusions: These results suggest high occurrence of phenotypic G-6-PD deficiency in Hausa ethnics of Kano with lower enzyme status among males living with G-6-PD deficiency.

A chloromethyl-triazole fluorescent chemosensor for O6-methylguanine DNA methyltransferase.

Fluorescent chemosensors offer a direct means of measuring enzyme activity for cancer diagnosis, predicting drug resistance, and aiding in the discovery of new anticancer drugs. O6-methylguanine DNA methyltransferase (MGMT) is a predictor of resistance towards anticancer alkylating agents such as temozolomide. Using the fluorescent molecular rotor, 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ), we synthesized, and evaluated a MGMT fluorescent chemosensor derived from a chloromethyl-triazole covalent inhibitor, AA-CW236, a non-pseudosubstrate of MGMT. Our fluorescence probe covalently labelled the MGMT active site C145, producing a 18-fold increase in fluorescence. Compared to previous fluorescent probes derived from a substrate-based inhibitor, our probe had improved binding and reaction rate. Overall, our chloromethyl triazole-based fluorescence MGMT probe is a promising tool for measuring MGMT activity to predict temozolomide resistance.

The influence of olive leaf extract on the activity of antioxidant enzymes in the Hemolymph of Galleria mellonella (L.) (Lepidoptera: Pyralidae)

The present study has aimed to examine the effects of olive leaf extract on the antioxidant enzyme activity of the invertebrate model organism Galleria mellonella L. (Lepidoptera: Pyralidae) hemolymph. For this purpose, after the olive leaves collected from Çanakkale province were dried at room temperature, the ethanolic extract was obtained with a soxhlet. After the ethanol was removed from the obtained extract in the rotary evaporator, the obtained dry matter was prepared in the phosphate buffer salt, 72 mg mL-1 as the highest dose and the lowest 0.010 mg mL-1 and injected into the larvae reared for the experiment. Hemolymph was collected at 4, 8, 12, 16, and 24-hours post-injection. Catalase (CAT) and superoxide dismutase (SOD) enzyme activities and malondialdehyde (MDA) formation levels were determined spectrophotometrically in the collected hemolymph. According to the results obtained, olive leaf extract decreased CAT and SOD activity in G. mellonella hemolymph at certain doses and increased the amount of MDA. For all enzymes, group, dose, and group-dose interactions were statistically significant. In addition, as a result of the examination made in terms of time, it was seen that the measurement of enzyme activities at the 24th hour was significant. The results of our study show that the antioxidant capacity of the olive leaf cannot be transferred to other living things and even reduces the antioxidant capacity of other organisms.

Fungal community structure shifts in litter degradation along forest succession induced by pine wilt disease

Fungi play a crucial role in decomposing litter and facilitating the energy flow between aboveground plants and underground soil in forest ecosystems. However, our understanding how the fungal community involved in litter decomposition responds during forest succession, particularly in disease-driven succession, is still limited. This study investigated the activity of degrading enzyme, fungal community, and predicted function in litter after one year of decomposition in different types of forests during a forest succession gradient from coniferous to deciduous forest, induced by pine wilt disease. The results showed that the weight loss of needles/leaves and twigs did not change along the succession process, but twigs degraded faster than needles/leaves in both pure pine forest and mixed forest. In pure pine forest, peak activities of enzymes involved in carbon degradation (β-cellobiosidase, β-glucosidase, β-D-glucuronidase, β-xylosidase), nitrogen degradation (N-acetyl-glucosamidase), and organic phosphorus degradation (phosphatase) were observed in needles, which subsequently declined. The fungal diversity and evenness (Shannon’s diversity and Shannon's evenness) dropped in twig from coniferous forest to mixed forest during the succession. The dominant phyla in needle/leaf and twig litters were Ascomycota (46.9%) and Basidiomycota (38.9%), with Lambertella pruni and Chalara hughesii identified as the most abundant indicator species. Gymnopus and Desmazierella showed positively correlations with most measured enzyme activities. Functionally, saprotrophs constituted the main trophic mode (47.65%), followed by Pathotroph-Saprotroph-Symbiotroph (30.95%) and Saprotroph-Symbiotroph (10.57%). The fungal community and predicted functional structures in both litter types shifted among different forest types along the succession. These findings indicate that the fungal community in litter decomposition responds differently to disease-induced succession, leading to significant shifts in both the fungal community structure and function.

Microbial carbon use efficiency and soil organic carbon stocks across an elevational gradient in the Peruvian Andes

Soils of mountain ecosystems are one of the most vulnerable ecosystems to climate change, while the ecosystem services they produce are significant and currently at risk. High altitude soils contain high C stocks, but due to difficult access to sites these areas are understudied. Moreover, how the C and N cycling is changing in response to climate change in these ecosystems, is still unclear. Microbial carbon use efficiency (CUE) and its dependency on the environmental constraints along the altitudinal gradients is one important unknown factor. Here we present results from an altitudinal gradient study (3500 to 4500 m a.s.l.) from a Polylepis forest in the Peruvian Andes. We measured the soil organic carbon (SOC) stocks and microbial metabolic CUE by 13C glucose tracing and microbial resource use efficiency (CUEC:N) based on enzyme activity measurements. We expected to find an increase in SOC stock, microbial nutrient limitations, and lower CUE with elevation. SOC stocks depended on soil development and followed a unimodal curve that peaks at 4000 m in two of the three studied valleys. Neither 13CUE nor CUEC:N changed significantly with altitude. Soil C:N ratio, β-glucosidase, chitinase, and phosphatase enzyme activities increased with elevation, but peroxidase activity decreased with elevation. We suggest that more labile organic matter left at high elevation could compensate for the increasing nutrient limitation at high elevation, resulting in no noticeable change in CUE with elevation.

PEG-6000 Priming Improves Aged Soybean Seed Vigor via Carbon Metabolism, ROS Scavenging, Hormone Signaling, and Lignin Synthesis Regulation

Seed priming, a valuable seed pretreatment method widely employed in agricultural production, counteracts the decline in seed vigor attributed to aging and deterioration. However, PEG priming effectively enhances the vigor of aged soybean seeds. In this study, “TONGDOU13” soybean seeds were subjected to PEG-6000 priming at varying concentrations (10%, 20%, 30%, 40%) for three different durations (12 h, 24 h, 36 h). The results showed that a 24 h priming with 30% PEG-6000 significantly enhances the vigor of aged soybean seeds. To elucidate the mechanism underlying the heightened vigor resulting from PEG-6000 priming, we employed transcriptome sequencing and physiological–biochemical tests. Transcriptome sequencing analysis showed the significant down-regulation of carbon metabolism-related genes post PEG-6000 priming, which facilitated energetically efficient germination. Five peroxidase-encoding genes displayed significant up-regulation, promoting the conversion of coumaryl alcohol to hydroxy-phenyl lignin, a probable catalyst for augmented seed vigor. SOD and GST genes were significantly up-regulated, enhancing the scavenging ability of reactive oxygen species (ROS). The concurrent up-regulation of brassinolide (BR) and auxin (IAA) signals countered ABA signaling, thereby promoting aged seed germination. Further investigation included the measurements of antioxidant enzyme activity, hormone levels, and lignin content. Notably, primed aged seeds exhibited enhanced ROS scavenging ability, and increased lignin, BR, and IAA contents. Therefore, PEG priming may improve aged soybean seed vigor through the co-regulation of carbon metabolism, ROS scavenging, hormone signaling, and lignin synthesis. This study will be vital for preserving germplasm resources and reutilizing aged soybean seeds.

Recombinant Organophosphorus acid anhydrolase (OPAA) enzyme-carbon quantum dot (CQDs)-immobilized thin film biosensors for the specific detection of Ethyl Paraoxon and Methyl Parathion in water resources

Organophosphates pesticide (OP) toxicity through water resources is a large concern globally among all the emerging pollutants. Detection of OPs is a challenge which needs to be addressed considering the hazardous effects on the health of human beings. In the current research thin film biosensors of recombinant, Organophosphorus acid anhydrolase (OPAA) enzyme along with carbon quantum dots (CQDs) immobilized in thin films were developed. OPAA-CQDs thin film biosensors were used for the specific detection of two OPs Ethyl Paraoxon (EP) and Methyl Parathion (MP) in river water and household water supply. Recombinant OPAA enzyme was expressed in E. Coli, purified and immobilized on the CQD containing chitosan thin films. The CQDs used for this purpose were developed by a one-pot hydrothermal method from phthalic acid and Tri ethylene diamine. The properties of CQDs, OPAA and thin films were characterized using techniques like XPS, TEM, XRD, enzyme activity and CLSM measurements. Biosensing studies of EP and MP were performed by taking fluorescence measurements using a fiber optic spectrometer. The analytical parameters of biosensing were compared against an estimation carried out using the HPLC method. The biosensing performance indicates that the OPAA-CQDs thin film-based biosensors were able to detect both EP and MP in a range of 0–100 μM having a detection limit of 0.18 ppm/0.69 ppm for EP/MP, respectively with a response time of 5 min. The accuracy of estimation of EP/MP when spiked in water resources lie in the range of ∼100–102% which clearly indicates the OPAA-CQD based thin film biosensors can function as a point-of-use method for the detection of OP pesticides in complex water resources.

Pyruvate dehydrogenase is a potential mitochondrial off-target for gentamicin based on in silico predictions and in vitro inhibition studies

During the drug development process, organ toxicity leads to an estimated failure of one-third of novel chemical entities. Drug-induced toxicity is increasingly associated with mitochondrial dysfunction, but identifying the underlying molecular mechanisms remains a challenge. Computational modeling techniques have proven to be a good tool in searching for drug off-targets. Here, we aimed to identify mitochondrial off-targets of the nephrotoxic drugs tenofovir and gentamicin using different in silico approaches (KRIPO, ProBis and PDID). Dihydroorotate dehydrogenase (DHODH) and pyruvate dehydrogenase (PDH) were predicted as potential novel off-target sites for tenofovir and gentamicin, respectively. The predicted targets were evaluated in vitro, using (colorimetric) enzymatic activity measurements. Tenofovir did not inhibit DHODH activity, while gentamicin potently reduced PDH activity. In conclusion, the use of in silico methods appeared a valuable approach in predicting PDH as a mitochondrial off-target of gentamicin. Further research is required to investigate the contribution of PDH inhibition to overall renal toxicity of gentamicin.

Paper-based electrodes as a tool for detecting ligninolytic enzymatic activities

Lignin is the most important natural source of aromatic compounds. The valorisation of lignin into aromatics requires fractionation steps that can be catalysed by ligninolytic enzymes. However, one of the main limitations of biological lignin fractionation is the low efficiency of biocatalysts; it is therefore crucial to enhance or to identify new ligninolytic enzymes. Currently, the screening of ligninolytic activities on lignin polymers represents a technological bottenleck and hinders the characterization and the discovery of efficient ligninolytic biocatalysts. An efficient and fast method for the measurement of such enzymatic activities is therefore required. In this work, we present a new electrochemical tool based on lignin-coated paper electrodes for the detection and the characterization of ligninolytic activity. The suitability of this method is demonstrated using a catalase-peroxidase isolated from Thermobacillus xylanilyticus.

Chrysin 7-O-β-D-glucuronide, a dual inhibitor of SARS-CoV-2 3CLpro and PLpro, for the prevention and treatment of COVID-19

The emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) resulted in the coronavirus disease 2019 (COVID-19) pandemic. Given the advent of subvariants, there is an urgent need to develop novel drugs. The aim of this study was to find SARS-CoV-2 inhibitors from Scutellaria baicalensis Georgi targeting the proteases 3CLpro and PLpro. After screening 25 flavonoids, chrysin 7-O-β-D-glucuronide was found to be a potent inhibitor of SARS-CoV-2 on Vero E6 cells, with half-maximal effective concentration of 8.72 µM. Surface plasmon resonance assay, site-directed mutagenesis and enzymatic activity measurements indicated that chrysin-7-O-β-D-glucuronide inhibits SARS-CoV-2 by binding to H41 of 3CLpro, and K157 and E167 of PLpro. Hydrogen-deuterium exchange mass spectrometry analysis showed that chrysin-7-O-β-D-glucuronide changes the conformation of PLpro. Finally, chrysin 7-O-β-D-glucuronide was shown to have anti-inflammatory activity, mainly due to reduction of the levels of the pro-inflammatory cytokines interleukin (IL)-1β and IL-6.