Nouvelles méthodes électrochimiques pour le criblage d’inhibiteurs de transcétolases

Chloé Aymard 1
1 GEMBAS - Génie Enzymatique, Membrane Biomimétique et Assemblages Supramoléculaires
ICBMS - Institut de Chimie et Biochimie Moléculaires et Supramoléculaires
Abstract : This thesis focuses on the development of a new electrochemical method allowing the high throughputscreening of enzyme inhibitors. For this purpose, a target enzyme has been selected for its therapeutic interest,transketolase (TK): this enzyme is involved in many diseases (cancer, neurodegenerative diseases, diabetes ...) and inthe survival of pathogenic parasites. To measure TK activity, two reporter systems have been developed by usingelectrochemical plates, composed of 96 independent electrodes.The first one is based on a bienzymatic system, requiring the use of an auxiliary enzyme, galactose oxidase(GAOx), in its soluble form or immobilized in laponite. This enzyme is able to oxidize TK products and producehydrogen peroxide. The 96-well format allowed to quickly optimize the electrochemical detection of oxidase activityby intermittent pulse amperometry (IPA) of oxidase activity and only 10 minutes are required to perform 96simultaneous measurements. In parallel, in order to harness the 96-well electrochemical system, this detection ofoxidase activity was also carried out in 10 minutes using electrochemiluminescence. This method is more sensitiveand less variable than IPA but is limited to the use of soluble enzymes. However, the reaction conditions are notoptimal for the bienzymatic system (TK-GAOx): long incubation times are required and are poorly adapted for thescreening of TK inhibitors.A second reporter system no longer requiring an auxiliary enzyme and involving only one TK substrate hasbeen optimized. This system relies on the oxidation by ferricyanide of the reactional intermediate resulted of thebinding of the cofactor (thiamine pyrophosphate) and the substrate. This method allows to measure 96 TK activitiesin only 7 minutes and was easily used to screen an in-house chemical library. The screening of 1360 molecules leadto the identification of a new TK inhibitor with an IC50 of 63 μM. This electrochemical system was also used todetermine the mechanism of inhibition (partial non-competitive mechanism) and the associated inhibition constant(3.4 μM). These results are innovative in the field of electrochemistry and offer a wide range of applications forenzymatic activity screening or the screening of enzymes inhibitors
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Chloé Aymard. Nouvelles méthodes électrochimiques pour le criblage d’inhibiteurs de transcétolases. Biochimie, Biologie Moléculaire. Université de Lyon, 2018. Français. ⟨NNT : 2018LYSE1212⟩. ⟨tel-02002371⟩

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