High-throughput kinetics in drug discovery.

The importance of a drug's kinetic profile and interplay of structure-kinetic activity with PK/PD has long been appreciated in drug discovery. However, technical challenges have often limited detailed kinetic characterization of compounds to the latter stages of projects. This review highlights the advances that have been made in recent years in techniques, instrumentation, and data analysis to increase the throughput of detailed kinetic and mechanistic characterization, enabling its application earlier in the drug discovery process.

EnzymeML: seamless data flow and modeling of enzymatic data.

The design of biocatalytic reaction systems is highly complex owing to the dependency of the estimated kinetic parameters on the enzyme, the reaction conditions, and the modeling method. Consequently, reproducibility of enzymatic experiments and reusability of enzymatic data are challenging. We developed the XML-based markup language EnzymeML to enable storage and exchange of enzymatic data such as reaction conditions, the time course of the substrate and the product, kinetic parameters and the kinetic model, thus making enzymatic data findable, accessible, interoperable and reusable (FAIR). The feasibility and usefulness of the EnzymeML toolbox is demonstrated in six scenarios, for which data and metadata of different enzymatic reactions are collected and analyzed. EnzymeML serves as a seamless communication channel between experimental platforms, electronic lab notebooks, tools for modeling of enzyme kinetics, publication platforms and enzymatic reaction databases. EnzymeML is open and transparent, and invites the community to contribute. All documents and codes are freely available at https://enzymeml.org .

interferENZY: A Web-Based Tool for Enzymatic Assay Validation and Standardized Kinetic Analysis.

Enzymatic assays are widely employed to characterize important allosteric and enzyme modulation effects. The high sensitivity of these assays can represent a serious problem if the occurrence of experimental errors surreptitiously affects the reliability of enzyme kinetics results. We have addressed this problem and found that hidden assay interferences can be unveiled by the graphical representation of progress curves in modified reaction coordinates. To render this analysis accessible to users across all levels of expertise, we have developed a webserver, interferENZY, that allows (i) an unprecedented tight quality control of experimental data, (ii) the automated identification of small and major assay interferences, and (iii) the estimation of bias-free kinetic parameters. By eliminating the subjectivity factor in kinetic data reporting, interferENZY will contribute to solving the "reproducibility crisis" that currently challenges experimental molecular biology. The interferENZY webserver is freely available (no login required) at https://interferenzy.i3s.up.pt.

Major Improvements in Robustness and Efficiency during the Screening of Novel Enzyme Effectors by the 3-Point Kinetics Assay.

The throughput level currently reached by automatic liquid handling and assay monitoring techniques is expected to facilitate the discovery of new modulators of enzyme activity. Judicious and dependable ways to interpret vast amounts of information are, however, required to effectively answer this challenge. Here, the 3-point method of kinetic analysis is proposed as a means to significantly increase the hit success rates and decrease the number of falsely identified compounds (false positives). In this post-Michaelis-Menten approach, each screened reaction is probed in three different occasions, none of which necessarily coincide with the initial period of constant velocity. Enzymology principles rather than subjective criteria are applied to identify unwanted outliers such as assay artifacts, and then to accurately distinguish true enzyme modulation effects from false positives. The exclusion and selection criteria are defined based on the 3-point reaction coordinates, whose relative positions along the time-courses may change from well to well or from plate to plate, if necessary. The robustness and efficiency of the new method is illustrated during a small drug repurposing screening of potential modulators of the deubiquinating activity of ataxin-3, a protein implicated in Machado-Joseph disease. Apparently, intractable Z factors are drastically enhanced after (1) eliminating spurious results, (2) improving the normalization method, and (3) increasing the assay resilience to systematic and random variability. Numerical simulations further demonstrate that the 3-point analysis is highly sensitive to specific, catalytic, and slow-onset modulation effects that are particularly difficult to detect by typical endpoint assays.

Protein crystals as a key for deciphering macromolecular crowding effects on biological reactions.

When placed in the same environment, biochemically unrelated macromolecules influence each other's biological function through macromolecular crowding (MC) effects. This has been illustrated in vitro by the effects of inert polymers on protein stability, protein structure, enzyme kinetics and protein aggregation kinetics. While a unified way to quantitatively characterize MC is still lacking, we show that the crystal solubility of lysozyme can be used to predict the influence of crowding agents on the catalytic efficiency of this enzyme. In order to capture general enthalpic effects, as well as hard entropic effects that are specific of large molecules, we tested sucrose and its cross-linked polymer Ficoll-70 as additives. Despite the different conditions of pH and ionic strength adopted, both the crystallization and the enzymatic assays point to an entropic contribution of approximately -1 kcal mol-1 caused by MC. Our results demonstrate that the thermodynamic activity of proteins is markedly increased by the reduction of accessible volume caused by the presence of macromolecular cosolutes. Unlike what is observed in protein folding studies, this MC effect cannot be reproduced using equivalent concentrations of monomeric crowding units. Applicable to any crystallizable protein, the thermodynamic interpretation of MC based on crystal solubility is expected to help in elucidating the full extent and importance of hard-type interactions in the crowded environment of the cell.

A simple linearization method unveils hidden enzymatic assay interferences.

Enzymes are among the most important drug targets in the pharmaceutical industry. The bioassays used to screen enzyme modulators can be affected by unaccounted interferences such as time-dependent inactivation and inhibition effects. Using procaspase-3, caspase-3, and α-thrombin as model enzymes, we show that some of these effects are not eliminated by merely ignoring the reaction phases that follow initial-rate measurements. We thus propose a linearization method (LM) for detecting spurious changes of enzymatic activity based on the representation of progress curves in modified coordinates. This method is highly sensitive to signal readout distortions, thereby allowing rigorous selection of valid kinetic data. The method allows the detection of assay interferences even when their occurrence is not suspected a priori. By knowing the assets and liabilities of the bioassay, enzymology results can be reported with enhanced reproducibility and accuracy. Critical analysis of full progress curves is expected to help discriminating experimental artifacts from true mechanisms of enzymatic inhibition.

A new topical formulation for psoriasis: development of methotrexate-loaded nanostructured lipid carriers.

The aim of the present work was to develop and assess the potential of nanostructured lipid carriers (NLCs) loaded with methotrexate as a new approach for topical therapy of psoriasis. Methotrexate-loaded NLCs were prepared via a modified hot homogenization combined with ultrasonication techniques using either polysorbate 60 (P60) or 80 (P80) as surfactants. The produced NLCs were within the nanosized range (274-298 nm) with relatively low polydispersity index (<0.25) and zeta potential values around -40 mV. NLCs demonstrated storage stability at 25°C up to 28 days. The entrapment efficiency of methotrexate in NLC-P60 and -P80 was ∼65%. Cryo-SEM images showed the spherical shape of the empty and methotrexate-loaded NLCs. FT-IR confirmed methotrexate presence within the NLCs. The in vitro release of methotrexate from the NLCs followed a fast release pattern reaching ∼70% in 2h. In vitro skin penetration study demonstrated that methotrexate-loaded NLCs-P60 had higher skin penetration when compared to free methotrexate, suggesting a significant role of drug-nanocarriers on topical administration. Methotrexate-loaded NLC-P60 provided drug fluxes of 0.88 µg/cm(2)/h, higher (P<0.001) than with the free drug (control, 0.59 µg/cm(2)/h). The results indicate the potential of NLCs for the delivery of methotrexate to topical therapy of psoriasis.