scholarly journals Coevolution of both Thermostability and Activity of Polyphosphate Glucokinase from Thermobifida fusca YX

2018 ◽  
Vol 84 (16) ◽  
Author(s):  
Wei Zhou ◽  
Rui Huang ◽  
Zhiguang Zhu ◽  
Yi-Heng P. Job Zhang
Keyword(s):  
High Activity ◽  
Double Layer ◽  
High Throughput ◽  
High Throughput Screening ◽  
Specific Activity ◽  
Colorimetric Assay ◽  
Petri Dish ◽  
Rapid Identification ◽  
Thermobifida Fusca ◽  
Content Type

ABSTRACT Thermostability and specific activity of enzymes are two of the most important properties for industrial biocatalysts. Here, we developed a petri dish-based double-layer high-throughput screening (HTS) strategy for rapid identification of desired mutants of polyphosphate glucokinase (PPGK) from a thermophilic actinobacterium, Thermobifida fusca YX, with both enhanced thermostability and activity. Escherichia coli colonies representing a PPGK mutant library were grown on the first-layer Phytagel-based plates, which can remain solid for 1 h, even at heat treatment temperatures of more than 100°C. The second layer that was poured on the first layer contained agarose, substrates, glucose 6-phosphate dehydrogenase (G6PDH), the redox dye tetranitroblue tetrazolium (TNBT), and phenazine methosulfate. G6PDH was able to oxidize the product from the PPGK-catalyzed reaction and generate NADH, which can be easily examined by a TNBT-based colorimetric assay. The best mutant obtained after four rounds of directed evolution had a 7,200-fold longer half-life at 55°C, 19.8°C higher midpoint of unfolding temperature (Tm), and a nearly 3-fold enhancement in specific activities compared to those of the wild-type PPGK. The best mutant was used to produce 9.98 g/liter myo-inositol from 10 g/liter glucose, with a theoretical yield of 99.8%, along with two other hyperthermophilic enzymes at 70°C. This PPGK mutant featuring both great thermostability and high activity would be useful for ATP-free production of glucose 6-phosphate or its derived products.IMPORTANCE Polyphosphate glucokinase (PPGK) is an enzyme that transfers a terminal phosphate group from polyphosphate to glucose, producing glucose 6-phosphate. A petri dish-based double-layer high-throughput screening strategy was developed by using ultrathermostable Phytagel as the first layer instead of agar or agarose, followed by a redox dye-based assay for rapid identification of ultrathermostable PPGK mutants. The best mutant featuring both great thermostability and high activity could produce glucose 6-phosphate from glucose and polyphosphate without in vitro ATP regeneration.

scholarly journals Simple Colorimetric Trypanothione Reductase-Based Assay for High-Throughput Screening of Drugs against Leishmania Intracellular Amastigotes

2013 ◽  
Vol 58 (1) ◽  
pp. 527-535 ◽  
Author(s):  
Erika van den Bogaart ◽  
Gerard J. Schoone ◽  
Paul England ◽  
Dorien Faber ◽  
Kristina M. Orrling ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Genetic Recombination ◽  
Colorimetric Assay ◽  
Reference Method ◽  
Published Data ◽  
Content Type ◽  
Intracellular Amastigotes ◽  
Efficient Test ◽  
Enzymatic Reduction

ABSTRACTCritical to the search for new anti-leishmanial drugs is the availability of high-throughput screening (HTS) methods to test chemical compounds against the relevant stage for pathogenesis, the intracellular amastigotes. Recent progress in automated microscopy and genetic recombination has produced powerful tools for drug discovery. Nevertheless, a simple and efficient test for measuring drug activity againstLeishmaniaclinical isolates is lacking. Here we describe a quantitative colorimetric assay in which the activity of aLeishmanianative enzyme is used to assess parasite viability. Enzymatic reduction of disulfide trypanothione, monitored by a microtiter plate reader, was used to quantify the growth ofLeishmaniaparasites. An excellent correlation was found between the optical density at 412 nm and the number of parasites inoculated. Pharmacological validation of the assay was performed against the conventional alamarBlue method for promastigotes and standard microscopy for intracellular amastigotes. The activity of a selected-compound panel, including several anti-leishmanial reference drugs, demonstrated high consistency between the newly developed assay and the reference method and corroborated previously published data. Quality assessment with standard measures confirmed the robustness and reproducibility of the assay, which performed in compliance with HTS requirements. This simple and rapid assay provides a reliable, accurate method for screening anti-leishmanial agents, with high throughput. The basic equipment and manipulation required to perform the assay make it easy to implement, simplifying the method for scoring inhibitor assays.

scholarly journals Investigating Molecular Mechanisms of Immunotoxicity and the Utility of ToxCast for Immunotoxicity Screening of Chemicals Added to Food

2021 ◽  
Vol 18 (7) ◽  
pp. 3332
Author(s):  
Olga V. Naidenko ◽  
David Q. Andrews ◽  
Alexis M. Temkin ◽  
Tasha Stoiber ◽  
Uloma Igara Uche ◽  
...  
Keyword(s):  
Immune System ◽  
High Throughput ◽  
Environmental Protection Agency ◽  
High Throughput Screening ◽  
Molecular Mechanisms ◽  
Specific Activity ◽  
Laboratory Animals ◽  
In Vitro Assays ◽  
Toxicological Studies

The development of high-throughput screening methodologies may decrease the need for laboratory animals for toxicity testing. Here, we investigate the potential of assessing immunotoxicity with high-throughput screening data from the U.S. Environmental Protection Agency ToxCast program. As case studies, we analyzed the most common chemicals added to food as well as per- and polyfluoroalkyl substances (PFAS) shown to migrate to food from packaging materials or processing equipment. The antioxidant preservative tert-butylhydroquinone (TBHQ) showed activity both in ToxCast assays and in classical immunological assays, suggesting that it may affect the immune response in people. From the PFAS group, we identified eight substances that can migrate from food contact materials and have ToxCast data. In epidemiological and toxicological studies, PFAS suppress the immune system and decrease the response to vaccination. However, most PFAS show weak or no activity in immune-related ToxCast assays. This lack of concordance between toxicological and high-throughput data for common PFAS indicates the current limitations of in vitro screening for analyzing immunotoxicity. High-throughput in vitro assays show promise for providing mechanistic data relevant for immune risk assessment. In contrast, the lack of immune-specific activity in the existing high-throughput assays cannot validate the safety of a chemical for the immune system.

scholarly journals A High-Throughput Approach To Identify Compounds That Impair Envelope Integrity in Escherichia coli

2016 ◽  
Vol 60 (10) ◽  
pp. 5995-6002 ◽  
Author(s):  
Kristin R. Baker ◽  
Bimal Jana ◽  
Henrik Franzyk ◽  
Luca Guardabassi
Keyword(s):  
Escherichia Coli ◽  
High Throughput ◽  
High Throughput Screening ◽  
Gram Negative Bacteria ◽  
Chromogenic Substrate ◽  
Intrinsic Resistance ◽  
Gram Negative ◽  
Content Type ◽  
E Coli ◽  
Screening Platform

ABSTRACTThe envelope of Gram-negative bacteria constitutes an impenetrable barrier to numerous classes of antimicrobials. This intrinsic resistance, coupled with acquired multidrug resistance, has drastically limited the treatment options against Gram-negative pathogens. The aim of the present study was to develop and validate an assay for identifying compounds that increase envelope permeability, thereby conferring antimicrobial susceptibility by weakening of the cell envelope barrier in Gram-negative bacteria. A high-throughput whole-cell screening platform was developed to measureEscherichia colienvelope permeability to a β-galactosidase chromogenic substrate. The signal produced by cytoplasmic β-galactosidase-dependent cleavage of the chromogenic substrate was used to determine the degree of envelope permeabilization. The assay was optimized by using known envelope-permeabilizing compounds andE. coligene deletion mutants with impaired envelope integrity. As a proof of concept, a compound library comprising 36 peptides and 45 peptidomimetics was screened, leading to identification of two peptides that substantially increased envelope permeability. Compound 79 reduced significantly (from 8- to 125-fold) the MICs of erythromycin, fusidic acid, novobiocin and rifampin and displayed synergy (fractional inhibitory concentration index, <0.2) with these antibiotics by checkerboard assays in two genetically distinctE. colistrains, including the high-risk multidrug-resistant, CTX-M-15-producing sequence type 131 clone. Notably, in the presence of 0.25 μM of this peptide, both strains were susceptible to rifampin according to the resistance breakpoints (R> 0.5 μg/ml) for Gram-positive bacterial pathogens. The high-throughput screening platform developed in this study can be applied to accelerate the discovery of antimicrobial helper drug candidates and targets that enhance the delivery of existing antibiotics by impairing envelope integrity in Gram-negative bacteria.

scholarly journals The micro-Petri dish, a million-well growth chip for the culture and high-throughput screening of microorganisms

2007 ◽  
Vol 104 (46) ◽  
pp. 18217-18222 ◽  
Author(s):  
C. J. Ingham ◽  
A. Sprenkels ◽  
J. Bomer ◽  
D. Molenaar ◽  
A. van den Berg ◽  
...  
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Petri Dish

High-throughput screening in the diagnostics industry

2002 ◽  
Vol 30 (4) ◽  
pp. 794-797 ◽  
Author(s):  
S. Wilson ◽  
S. Howell
Keyword(s):  
Product Development ◽  
High Throughput ◽  
High Throughput Screening ◽  
Rapid Identification ◽  
Target Antigen ◽  
Cycle Times ◽  
Development Cycle ◽  
Speed Up ◽  
Product Development Cycle ◽  
Automated Screening

The diagnostics industry is constantly under pressure to bring innovation quicker to market and so the impetus to speed up product-development cycle times becomes greater. There are a number of steps in the product-development cycle where the application of high-throughput screening can help. In the case of lateral-flow immunodiagnostics the selection of antibody reagents is paramount. In particular, rapid identification of antibody pairs that are able to ‘sandwich’ around the target antigen is required. One screen that has been applied successfully is the use of surface plasmon resonance biosensors like Biacore®. Using such a system one can evaluate over 400 antibody pairings in under 5 days. Conventional approaches to screen this number of antibody pairs would take many months. Other automated screening systems like DELFIA® can be used in processing the vast amount of tests required for clinical trials. In addition, the use of robotics to automate routine product testing can be used to shorten the product-development cycle.

Phospholipid/Polydiacetylene Vesicle-Based Colorimetric Assay for High-Throughput Screening of Bacteriocins and Halocins

2016 ◽  
Vol 182 (1) ◽  
pp. 142-154 ◽  
Author(s):  
Manoj Kumar Yadav ◽  
Vijay Kumar ◽  
Bijender Singh ◽  
Santosh Kumar Tiwari
Keyword(s):  
High Throughput ◽  
High Throughput Screening ◽  
Colorimetric Assay

scholarly journals A Fluorescence-Based High-Throughput Screen to Identify Small Compound Inhibitors of the Genotype 3a Hepatitis C Virus RNA Polymerase

2013 ◽  
Vol 18 (9) ◽  
pp. 1027-1034 ◽  
Author(s):  
Auda A. Eltahla ◽  
Kurt Lackovic ◽  
Christopher Marquis ◽  
John-Sebastian Eden ◽  
Peter A. White
Keyword(s):  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Rna Polymerase ◽  
High Throughput ◽  
High Throughput Screening ◽  
De Novo ◽  
Specific Activity ◽  
Hcv Rna ◽  
High Throughput Screen ◽  
Rdrp Activity

The hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) plays an essential role in the replication of HCV and is a key target for novel antiviral therapies. Several RdRp inhibitors are in clinical trials and have increased response rates when combined with current interferon-based therapies for genotype 1 (G1) HCV patients. These inhibitors, however, show poor efficacy against non-G1 genotypes, including G3a, which represents ~20% of HCV cases globally. Here, we used a commercially available fluorescent dye to characterize G3a HCV RdRp in vitro. RdRp activity was assessed via synthesis of double-stranded RNA from the single-stranded RNA poly(C) template. The assay was miniaturized to a 384-well microplate format and a pilot high-throughput screen was conducted using 10,208 “lead-like” compounds, randomly selected to identify inhibitors of HCV G3a RdRp. Of 150 compounds demonstrating greatest inhibition, 10 were confirmed using both fluorescent and radioactive assays. The top two inhibitors (HAC001 and HAC002) demonstrated specific activity, with an IC50 of 12.7 µM and 1.0 µM, respectively. In conclusion, we describe simple, fluorescent-based high-throughput screening (HTS) for the identification of inhibitors of de novo RdRp activity, using HCV G3a RdRp as the target. The HTS system could be used against any positive-sense RNA virus that cannot be cultured.

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