Fluorescent Enzymatic Assay Research Articles

Snakebite drug discovery: high-throughput screening to identify novel snake venom metalloproteinase toxin inhibitors.

Snakebite envenoming results in ∼100,000 deaths per year, with close to four times as many victims left with life-long sequelae. Current antivenom therapies have several limitations including high cost, variable cross-snake species efficacy and a requirement for intravenous administration in a clinical setting. Next-generation snakebite therapies are being widely investigated with the aim to improve cost, efficacy, and safety. In recent years several small molecule drugs have shown considerable promise for snakebite indication, with oral bioavailability particularly promising for community delivery rapidly after a snakebite. However, only two such drugs have entered clinical development for snakebite. To offset the risk of attrition during clinical trials and to better explore the chemical space for small molecule venom toxin inhibitors, here we describe the first high throughput drug screen against snake venom metalloproteinases (SVMPs)-a pathogenic toxin family responsible for causing haemorrhage and coagulopathy. Following validation of a 384-well fluorescent enzymatic assay, we screened a repurposed drug library of 3,547 compounds against five geographically distinct and toxin variable snake venoms. Our drug screen resulted in the identification of 14 compounds with pan-species inhibitory activity. Following secondary potency testing, four SVMP inhibitors were identified with nanomolar EC50s comparable to the previously identified matrix metalloproteinase inhibitor marimastat and superior to the metal chelator dimercaprol, doubling the current global portfolio of SVMP inhibitors. Following analysis of their chemical structure and ADME properties, two hit-to-lead compounds were identified. These clear starting points for the initiation of medicinal chemistry campaigns provide the basis for the first ever designer snakebite specific small molecules.

Diacylglycerol acyltransferase (DGAT) in Crangon crangon and Pandalus montagui (Decapoda, Caridea) - Implications for lipid storage capacities and life history traits.

Lipids play essential roles in cell-structuring, cell-signaling, and as efficient metabolic energy stores. Lipid storage capacities determine life history traits of organisms and, thus, their ecological function. Among storage lipids, triacylglycerols (TAGs) are widespread in marine invertebrates. However, abilities to accumulate TAGs can vary even between closely related species, such as the caridean shrimps Crangon crangon and Pandalus montagui. The first species shows low TAG levels throughout the year in the main storage organ, the midgut gland, while the latter accumulates high TAG-levels, peaking in summer. TAGs synthesis is facilitated by the terminal step of the Kennedy-pathway, where the enzyme diacylglycerol-acyltransferase (DGAT) catalyzes the esterification of diacylglycerols with activated fatty acids. We investigated DGAT activity in the midgut gland using a fluorescent enzyme assay. Sequence information was extracted from whole transcriptome shotgun assembly data, that was publicly available on NCBI, and catalytic properties were deduced from molecular structure analysis. C. crangon showed significantly lower TAG synthesis rates than P. montagui, which explains the native TAG levels. Transcriptome data yielded several isoforms of DGAT enzymes in both species. C. crangon DGAT showed point mutations, which are capable of obstructing the catalytic capacity. The consequences are limited starvation resistance and, thus, presumably restricting C. crangon to a habitat with year-round sufficient food. In contrast, higher TAG synthesis rates presumably enable P. montagui to extend into northern subarctic habitats with limited food availability in winter. Moreover, the limited TAG synthesis and accumulation in the midgut gland may force C. crangon to direct energy into the ovaries, which results in multiple spawnings.

Single-Cell Enzymatic Screening for Epithelial Mesenchymal Transition with an Ultrasensitive Superwetting Droplet-Array Microchip.

The phenotypic changes of circulating tumor cells (CTCs) during the epithelial-mesenchymal transition (EMT) have been a hot topic in tumor biology and cancer therapeutic development. Here, an integrated platform of single-cell fluorescent enzymatic assays with superwetting droplet-array microchips (SDAM) for ultrasensitive functional screening of epithelial-mesenchymal sub-phenotypes of CTCs is reported. The SDAM can generate high-density, volume well-defined droplet (0.66 nL per droplet) arrays isolating single tumor cells via a discontinuous dewetting effect. It enables sensitive detection of MMP9 enzyme activities secreted by single tumor cells, correlating to their epithelial-mesenchymal sub-phenotypes. In the pilot clinical double-blind tests, the authors have demonstrated that SDAM assays allow for rapid identification and functional screening of CTCs with different epithelial-mesenchymal properties. The consistency with the clinical outcomes validates the usefulness of single-cell secreted MMP9 as a biomarker for selective CTC screening and tumor metastasis monitoring. Convenient addressing and recovery of individual CTCs from SDAM have been demonstrated for gene mutation sequencing, immunostaining, and transcriptome analysis, revealing new understandings of the signaling pathways between MMP9 secretion and the EMT regulation of CTCs. The SDAM approach combined with sequencing technologies promises to explore the dynamic EMT plasticity of tumors at the single-cell level.

Qualitative and quantitative comparison of allergen component-specific to birch and grass analyzed by ImmunoCAP assay and Euroline immunoblot test.

Background. In the diagnostic work up of allergy, determining allergen component-specific immunoglobulin E (IgE) is important for diagnosis, prognosis and choice of treatment. Objective. The purpose of this study was to evaluate the performance of the immunoblotting assay (Euroline) in detection of IgE antibodies against timothy grass and birch pollen allergen components compared to fluorescent enzyme assay (ImmunoCAP, Phadia 250). Methods. A total of 128 serum samples from patients allergic to timothy grass and birch pollen were analysed. The levels of IgE antibodies to timothy grass and birch pollen were measured using Euroline DPA-Dx pollen 1 and ImmunoCAP assay. The two methods were then compared on binary (positive vs negative), semi-quantitative (IgE classes) and quantitative (concentration) levels. The two methods were also compared to results from skin prick testing. Results. The Euroline method showed a positive percentage agreement of 93% and negative percentage agreement of 94% with an overall accuracy of 94% when compared to ImmunoCAP. Kappa analysis showed moderate strength of agreement between the methods in determining IgE classes for 7/11 components tested. All components showed a positive correlation when analysed using Spearman's rank correlation. Conclusions. Overall, we found that there is good correlation between the Euroline and ImmunoCAP methods in measuring IgE sensitization.

The influence of UV light on the course of fluorescent enzyme assays

Experiments were carried out to illustrate the effect of UV light on the course of the enzymatic reaction of the coumarin derivative. Only the pulsating light of the UV diode gives the correct results for the determination of the kinetic constants of the enzymatic reaction. The enzyme concentration limit was found where the description of the M-M model breaks. It was shown that the system determines the kinetic parameters of enzymatic reactions: Vmax —the maximum rate of reaction and KM—the Michaelis constant. This method produces kinetic constants calculated from the changes in enzyme product concentration using the Michaelis-Menten model. To verify the results, we used a statistical analysis that checks the correctness of the model used.

Impact of twenty pesticides on soil carbon microbial functions and community composition

Pesticides are known to affect non-targeted soil microorganisms. Still, studies comparing the effect of multiple pesticides on a wide range of microbial endpoints associated with carbon cycling are scarce. Here, we employed fluorescence enzymatic assay and real-time PCR to evaluate the effect of 20 commercial pesticides, applied at their recommended dose and five times their recommended dose, on soil carbon cycling related enzymatic activities (α-1,4-glucosidase, β-1,4-glucosidase, β-d-cellobiohydrolase and β-xylosidase), and on the absolute abundance of functional genes (cbhl and chiA), in three different South Australian agricultural soils. The effects on cellulolytic and chitinolytic microorganisms, and the total microbial community composition were determined using shotgun metagenomic sequencing in selected pesticide-treated and untreated samples. The application of insecticides significantly increased the cbhl and chiA genes absolute abundance in the acidic soil. At the community level, insecticide fipronil had the greatest stimulating effect on cellulolytic and chitinolytic microorganisms, followed by fungicide metalaxyl-M and insecticide imidacloprid. A shift towards a fungal dominated microbial community was observed in metalaxyl-M treated soil. Overall, our results suggest that the application of pesticides might affect the soil carbon cycle and may disrupt the formation of soil organic matter and structure stabilisation.

First Fluorescent Acetylspermidine Deacetylation Assay for HDAC10 Identifies Selective Inhibitors with Cellular Target Engagement.

Histone deacetylases (HDACs) are important epigenetic regulators involved in many diseases, especially cancer. Five HDAC inhibitors have been approved for anticancer therapy and many are in clinical trials. Among the 11 zinc‐dependent HDACs, HDAC10 has received relatively little attention by drug discovery campaigns, despite its involvement, e. g., in the pathogenesis of neuroblastoma. This is due in part to a lack of robust enzymatic conversion assays. In contrast to the protein lysine deacetylase and deacylase activity of most other HDAC subtypes, it has recently been shown that HDAC10 has strong preferences for deacetylation of oligoamine substrates like acetyl‐putrescine or ‐spermidine. Hence, it is also termed a polyamine deacetylase (PDAC). Here, we present the first fluorescent enzymatic conversion assay for HDAC10 using an aminocoumarin‐labelled acetyl‐spermidine derivative to measure its PDAC activity, which is suitable for high‐throughput screening. Using this assay, we identified potent inhibitors of HDAC10‐mediated spermidine deacetylation in vitro. Based on the oligoamine preference of HDAC10, we also designed inhibitors with a basic moiety in appropriate distance to the zinc binding hydroxamate that showed potent inhibition of HDAC10 with high selectivity, and we solved a HDAC10‐inhibitor structure using X‐ray crystallography. We could demonstrate selective cellular target engagement for HDAC10 but a lysosomal phenotype in neuroblastoma cells that was previously associated with HDAC10 inhibition was not observed. Thus, we have developed new chemical probes for HDAC10 that allow further clarification of the biological role of this enzyme.

Fluorescent enzymatic assay for direct total polyphenol determination in food-related samples

A direct and simple fluorescent assay for the total polyphenol determination based on the bioconjugate formed between the laccase enzyme (TvL from Trametes versicolor) and carbon nanodots (CD) is developed. One of the most used reactions for the determination of phenols is based on the enzymatic reaction of their oxidation to quinones. In this work, CD has been biofunctionalized with TvL (TvL-CD) and employed as a fluorescent label to follow the enzymatic reaction. The bioconjugate was formed and characterized by spectroscopy and microscopy. The optimal TvL-CD ratio was established. The reaction between the bioconjugate and a phenolic compound such as gallic acid (GA) was followed by monitoring the fluorescence bioconjugate decrease due to the quenching effect of the quinones generated in the enzymatic reaction. These studies confirm that bioconjugation does not inhibit the enzymatic activity and the fluorescence decrease during the enzymatic reaction is mainly due to an electron transfer processes. Based on these results, a new method for the quantitative determination of polyphenols measured as GA concentration is developed. The detection and quantification limit was found to be 7.4 and 25 μM, respectively. Subsequently, the method has been applied to the direct determination of GA in wine, juice, and rice leaf extracts.

Fast screening of tyrosinase inhibitors from traditional Chinese medicinal plants by ligand fishing in combination with in situ fluorescent assay.

A simple and rapid method for screening of tyrosinase (TYR) inhibitors present in traditional Chinese medicines (TCMs) was developed by combining ligand fishing and the fluorescent enzymatic assay based on dopamine-functionalized carbon quantum dots (CQDs-Dopa). Ligands of the enzyme present in the TCM extractions were firstly adsorbed on the enzyme-modified magnetic beads, and then the beads were magnetically separated and subjected directly to the CQDs-Dopa-based fluorescent assay. Finally, compounds were desorbed from the "active" beads and identified with ultra-performance liquid chromatography-triple quadrupole mass spectrometry. A known natural TYR inhibitor quercetin was selected to assess the feasibility and quantification performance of this method, and good linearity in the range of 0.01-0.16mM (R2 = 0.992) with a low detection limit of 0.004mM was obtained. This method was then applied to screen TYR inhibitors present in Scutellaria baicalensis and Sophora flavescens. Six TYR inhibitors including baicalin (1), baicalein (2), wogonin (3), oroxylin A (4), kurarinone (5), and sophoraflavanone G (6) were found, among which 1-4 were firstly discovered in this work. This is the first report on the in situ assessment of the target compounds obtained by ligand fishing in the form of a mixture, which exhibited the combined advantages of specific extraction ability of ligand fishing and the high sensitivity of CQDs-based fluorescent assay, showing great potential for fast screening of enzyme inhibitors from TCMs.

In vitro effects of 95% khat ethanol extract (KEE) on human recombinant cytochrome P450 (CYP)1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2E1, CYP2J2 and CYP3A5.

Khat, a natural amphetamine-like psychostimulant plant, are widely consumed globally. Concurrent intake of khat and xenobiotics may lead to herb-drug interactions and adverse drug reactions (ADRs). This study is a continuation of our previous study, targeted to evaluate the in vitro inhibitory effects of khat ethanol extract (KEE) on human cytochrome (CYP) 1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2E1, CYP2J2, and CYP3A5, major human drug metabolizing enzymes. In vitro fluorescence enzyme assays were employed to assess CYPs inhibition with the presence and absence of various KEE concentrations. KEE reversibly inhibited CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2E1, CYP2J2 and CYP3A5 but not CYP1A2 with IC50 values of 25.5, 99, 4.5, 21, 27, 17, and 10μg/mL respectively. No irreversible inhibition of KEE on all the eight CYPs were identified. The Ki values of CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2E1, CYP2J2 and CYP3A5 were 20.9, 85, 4.8, 18.3, 59.3, 3, and 21.7μg/mL, respectively. KEE inhibited CYP2B6 via competitive or mixed inhibition; CYP2E1 via un-competitive or mixed inhibition; while CYP2A6, CYP2C8, CYP2C19, CYP2J2 and CYP3A5 via non-competitive or mixed inhibition. Caution should be taken by khat users who are on medications metabolized by CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2E1, CYP2J2, and CYP3A5.

Modulators of immunoregulatory exonucleases PLD3 and PLD4 identified by high-throughput screen

PLD3 and PLD4 have recently been revealed to be endosomal exonucleases that regulate the innate immune response by digesting the ligands of nucleic acid sensors. These enzymes can suppress RNA and DNA innate immune sensors like toll-like receptor 9, and PLD4-deficent mice exhibit inflammatory disease. Targeting these immunoregulatory enzymes presents an opportunity to indirectly regulate innate immune nucleic acid sensors that could yield immunotherapies, adjuvants, and nucleic acid drug stabilizers. To aid in delineating the therapeutic potential of these targets, we have developed a high-throughput fluorescence enzymatic assay to identify modulators of PLD3 and PLD4. Screening of a diversity library (N = 17952) yielded preferential inhibitors of PLD3 and PLD4 in addition to a PLD3 selective activator. The modulation models of these compounds were delineated by kinetic analysis. This work presents an inexpensive and simple method to identify modulators of these immunoregulatory exonucleases.

Integrase-derived peptides together with CD24-targeted lentiviral particles inhibit the growth of CD24 expressing cancer cells

The integration of viral DNA into the host genome is mediated by viral integrase, resulting in the accumulation of double-strand breaks. Integrase-derived peptides (INS and INR) increase the number of integration events, leading to escalated genomic instability that induces apoptosis. CD24 is a surface protein expressed mostly in cancer cells and is very rarely found in normal cells. Here, we propose a novel targeted cancer therapeutic platform based on the lentiviral integrase, stimulated by integrase-derived peptides, that are specifically delivered to cancerous cells via CD24 antigen-antibody targeting. INS and INR were synthesized and humanized and anti-CD24 antibodies were fused to the lentivirus envelope. The activity, permeability, stability, solubility, and toxicity of these components were analyzed. Cell death was measured by fluorescent microscopy and enzymatic assays and potency were tested in vitro and in vivo. Lentivirus particles, containing non-functional DNA led to massive cell death (40–70%). Raltegravir, an antiretroviral drug, inhibited the induction of apoptosis. In vivo, single and repeated administrations of INS/INR were well tolerated without any adverse effects. Tumor development in nude mice was significantly inhibited (by 50%) as compared to the vehicle arm. In summary, a novel and generic therapeutic platform for selective cancer cell eradication with excellent efficacy and safety are presented.

Fragment-Based Discovery of Irreversible Covalent Inhibitors of Cysteine Proteases Using Chlorofluoroacetamide Library.

Fragment-based approach combined with electrophilic reactive compounds is a powerful strategy to discover novel covalent ligands for protein target. However, the promiscuous reactivity often interferes with identification of the fragments possessing specific binding affinity to the targeted protein. In our study, we report the fragment-based covalent drug discovery using the chemically tuned weak reactivity of chlorofluoroacetamide (CFA). We constructed a small fragment library composed of 30 CFA-appended compounds and applied it to the covalent ligand screening for cysteine protease papain as a model protein target. Using the fluorescence enzymatic assay, we identified CFA-benzothiazole 30 as a papain inhibitor, which was found to irreversibly inactivate papain upon enzyme kinetic analysis. The formation of the covalent papain-30 adduct was confirmed using electrospray ionization mass spectrometry analysis. The activity-based protein profiling (ABPP) experiment using an alkynylated analog of 30 (i.e., 30-yne) revealed that 30-yne covalently labeled papain with high selectivity. These data demonstrate potential utility of the CFA-fragment library for de novo discovery of target selective covalent inhibitors.

Emerging Approaches for Fluorescence-Based Newborn Screening of Mucopolysaccharidoses.

Interest in newborn screening for mucopolysaccharidoses (MPS) is growing, due in part to ongoing efforts to develop new therapies for these disorders and new screening assays to identify increased risk for the individual MPSs on the basis of deficiency in the cognate enzyme. Existing tests for MPSs utilize either fluorescence or mass spectrometry detection methods to measure biomarkers of disease (e.g., enzyme function or glycosaminoglycans) using either urine or dried blood spot (DBS) samples. There are currently two approaches to fluorescence-based enzyme function assays from DBS: (1) manual reaction mixing, incubation, and termination followed by detection on a microtiter plate reader; and (2) miniaturized automation of these same assay steps using digital microfluidics technology. This article describes the origins of laboratory assays for enzyme activity measurement, the maturation and clinical application of fluorescent enzyme assays for MPS newborn screening, and considerations for future expansion of the technology.

Potent and selective inhibitors for M32 metallocarboxypeptidases identified from high-throughput screening of anti-kinetoplastid chemical boxes.

Enzymes of the M32 family are Zn-dependent metallocarboxypeptidases (MCPs) widely distributed among prokaryotic organisms and just a few eukaryotes including Trypanosoma brucei and Trypanosoma cruzi, the causative agents of sleeping sickness and Chagas disease, respectively. These enzymes are absent in humans and several functions have been proposed for trypanosomatid M32 MCPs. However, no synthetic inhibitors have been reported so far for these enzymes. Here, we present the identification of a set of inhibitors for TcMCP-1 and TbMCP-1 (two trypanosomatid M32 enzymes sharing 71% protein sequence identity) from the GlaxoSmithKline HAT and CHAGAS chemical boxes; two collections grouping 404 compounds with high antiparasitic potency, drug-likeness, structural diversity and scientific novelty. For this purpose, we adapted continuous fluorescent enzymatic assays to a medium-throughput format and carried out the screening of both collections, followed by the construction of dose-response curves for the most promising hits. As a result, 30 micromolar-range inhibitors were discovered for one or both enzymes. The best hit, TCMDC-143620, showed sub-micromolar affinity for TcMCP-1, inhibited TbMCP-1 in the low micromolar range and was inactive against angiotensin I-converting enzyme (ACE), a potential mammalian off-target structurally related to M32 MCPs. This is the first inhibitor reported for this family of MCPs and considering its potency and specificity, TCMDC-143620 seems to be a promissory starting point to develop more specific and potent chemical tools targeting M32 MCPs from trypanosomatid parasites.

Fluorescence enzymatic assay for bacterial polyphosphate kinase 1 (PPK1) as a platform for screening antivirulence molecules.

Inorganic polyphosphate (polyP) and its metabolic enzymes are important in several cellular processes related with virulence and antibiotic susceptibility. Accordingly, bacterial polyP synthesis has been proposed as a good target for designing novel antivirulence molecules as alternative to conventional antibiotics. In most pathogenic bacteria, polyphosphate kinase 1 (PPK1), in charge of polyP synthesis from ATP, is widely conserved. Current colorimetric and radioactive polyP synthesis enzymatic assays are not suitable for high-throughput screening of PPK1 inhibitors. Given the ability of polyP to modify the excitation-emission spectra of DAPI (4ʹ-6-diamidino-2-phenylindole), a fluorescence assay was previously developed by using a purified recombinant PPK1 enzyme from Escherichia coli. In this work we have developed a suitable methodology for high-throughput measurement of E. coli PPK1 activity. This platform can be used for the screening putative antimicrobial molecules for related enteropathogenic bacteria.

Comparison of specific IgE detection by immunoblotting and fluorescence enzyme assay with in vivo skin prick test

Diagnostic tools to identify allergens that cause allergic symptom is important part in the care of allergic patients. Detection of causative allergen can be performed by in vivo skin prick test (SPT) or in vitro tests for detection serum specific immunoglobulin E (sIgE). The common methods used are fluorescent enzyme assay and immunoblotting assay. We aim to evaluate performance of the two sIgE determination systems, immunoblotting assay (Euroline) and fluorescent enzyme assay (ImmunoCAP) in comparison with SPT. Two hundred and two participants with allergic diseases were enrolled. Sensitization to common allergens was identified using skin prick test and serum specific IgE assays with Euroline and ImmunoCAP. Both systems provide the result in the same unit and the same cut-off value (0.35 kUA/L). The specific IgE levels of 4 aeroallergens, 6 food allergens and 3 food allergen components were analyzed to evaluate the performance of both sIgE assays with SPT. When compared with the result of SPT, ImmunoCAP has 63.9-93.2% agreement and Euroline has 68.4-86.2% agreement for allergen detection. Both sIgE assays have significant correlation in measuring sIgE of almost all allergens (r=0.626-0.901, p< 0.001) except for dog. For food allergen components, both sIgE tests have outstanding correlation and agreement (r=0.816-0.952, p< 0.001; agreement =87.0-92.9%, respectively). The receiver-operating characteristic curve analysis indicated slight discrepancy of both sIgE assays. Both sIgE determination systems demonstrate fair to good performance when compared to SPT depending on type of allergens. The two sIgE determination systems had favorable correlation and agreement.

Novel Aryl‐Modified Benzoylamino‐N‐(5,6‐dimethoxy‐1H‐benzoimidazol‐2‐yl)‐heteroamides as Potent Inhibitors of Vascular Endothelial Growth Factor Receptors 1 and 2

Tumor angiogenesis has become an important target for antitumor therapy, with most current therapies aimed at blocking the vascular endothelial growth factor (VEGF) pathway. The VEGF and its receptors have been implicated as key factors in tumor angiogenesis and are major targets in cancer therapy. A series of aryl‐modified benzoylamino‐N‐(5,6‐dimethoxy‐1H‐benzoimidazol‐2‐yl)‐heteroamides were synthesized from 2‐amino‐5,6‐dimethoxy benzimidazole and aryl‐substituted benzoylamino hetero acids. The new compounds were tested for inhibition of VEGF receptors I and II (VEGFR‐1 and VEGFR‐2). Compound 6e displayed VEGFR‐2 inhibitory activity with a 50% inhibition concentration value as low as 0.020 μM in a homogeneous time‐resolved fluorescence enzymatic assay. VEGFR‐2 active compounds display good activity against VEGFR‐1 as well.

Evaluation of human microtubule affinity-regulating kinase 4 inhibitors: fluorescence binding studies, enzyme, and cell assays

Human microtubule affinity-regulating kinase 4 (MARK4) is considered as an encouraging drug target for the design and development of inhibitors to cure several life-threatening diseases such as Alzheimer disease, cancer, obesity, and type-II diabetes. Recently, we have reported four ligands namely, BX-912, BX-795, PKR-inhibitor, and OTSSP167 (hydrochloride) which bind preferentially to the two different constructs of human MARK4 containing kinase domain. To ensure the role of ubiquitin-associated (UBA) domain in the ligand binding, we made a newer construct of MARK4 which contains both kinase and UBA domains, named as MARK4-F3. We observed that OTSSP167 (hydrochloride) binds to the MARK4-F3 with a binding constant (K) of 3.16 × 106, M−1 (±.21). However, UBA-domain of MARK4-F3 doesn’t show any interaction with ligands directly as predicted by the molecular docking. To validate further, ATPase inhibition assays of all three constructs of MARK4 in the presence of mentioned ligands were carried out. An appreciable correlation between the binding experiments and ATPase inhibition assays of MARK4 was observed. In addition, cell-proliferation inhibition activity for all four ligands on the Human embryonic kidney (HEK-293) and breast cancer cell lines (MCF-7) was performed using MTT assay. IC50 values of OTSSP167 for HEK-293 and MCF-7 were found to be 58.88 (±1.5), and 48.2 (±1.6), respectively. OTSSP167 among all four inhibitors, showed very good enzyme inhibition activity against three constructs of MARK4. Moreover, all four inhibitors showed anti-neuroblastoma activity and anticancer properties. In conclusion, OTSSP167 may be considered as a promising scaffold to discover novel inhibitors of MARK4.

An Enzymatic Method for Methanol Quantification in Methanol/Ethanol Mixtures with a Microtiter Plate Fluorometer

In response to the need for a rapid, high-throughput screening of methanol contamination in spirits, a new microplate-based assay was developed. In this assay, alcohol oxidase first oxidizes methanol to formaldehyde, which is further oxidized to formate by formaldehyde dehydrogenase while reducing NAD+ to NADH. The latter product then reacts with resazurin under catalysis by FerB, a diaphorase-type enzyme, to give the highly fluorescent resorufin. These reactions are run simultaneously in 200 μL final volume in a 96-well plate and quantified using a plate reader and fluorescence detector. It is shown that the rate of fluorescence change is related to methanol and ethanol concentrations according to the rate law for two competing substrates. Quantification of methanol in real samples is carried out by applying the standard additions technique with four different spiking concentrations of the methanol standard; methanol content in the sample is calculated from the x-intercept of the fitted line. The high activity of FerB with resazurin and low rate of further conversion of resorufin to non-fluorescent dihydroresorufin indicate that FerB may be advantageous over commercially available diaphorases for use in fluorescence enzyme assays.