Comparing enzyme activity modifier equations through the development of global data fitting templates in Excel

Abstract

The classical way of defining enzyme inhibition has obscured the distinction between inhibitory effect and the inhibitor binding constant. This article examines the relationship between the simple binding curve used to define biomolecular interactions and the standard inhibitory term (1+([I]/Ki)). By understanding how this term relates to binding curves which are ubiquitously used to describe biological processes, a modifier equation which distinguishes between inhibitor binding and the inhibitory effect, is examined. This modifier equation which can describe both activation and inhibition is compared to standard inhibitory equations with the development of global data fitting templates in Excel and via the global fitting of these equations to simulated and previously published datasets. In both cases, this modifier equation was able to match or outperform the other equations by providing superior fits to the datasets. The ability of this single equation to outperform the other equations suggests an over-complication of the field. This equation and the template developed in this article should prove to be useful tools in the study of enzyme inhibition and activation.

Computer-Aided Discovery of Pentapeptide AEYTR as a Potent Acetylcholinesterase Inhibitor

“…The assay to measure AChE activity followed to AChE kit protocol (Cat. #KA1607) [30]. The reaction mixture was prepared in the 96-well microplates, consisted of 5 mL of 3 mM 5,5'-dithio-bis (2-nitrobenzoic acid), 5 mL of 75 mM acetylthiocholine iodide, 110 mL 0.1 M sodium phosphate buffer (pH 7.5) as working reagents and 120 mL of peptide solution as stock samples at different concentrations (25, 50, 100, 250, 500 ppm or 36, 75, 150, 376, 751 μM) and positive control (donepezil).…”

Response to the Article “Enzyme–Inhibitor Interactions and a Simple, Rapid Method for Determining Inhibition Modality”

“…This equation has been tested against the classical equations with real data and has been found to allow for an equivalent or improved fit in all cases. 3–5 The flexibility of this approach also allows the equation to be used to describe activators in addition to inhibitors. Any researchers can also quickly and easily test this approach with their own data and evaluate the fit against the classical models using a freely available Excel template.…”

“…Any researchers can also quickly and easily test this approach with their own data and evaluate the fit against the classical models using a freely available Excel template. 4 Therefore, it is a disservice to the research community for the authors to recommend constraining mechanistic studies to classical inhibition equations with clear mathematical limitations based on mechanistic models the authors concede are not valid.…”