Modélisation du mécanisme catalytique de l'urate oxydase

Abstract : In this work, a theoretical study has been carried our in order to understand the catalytic mechanism of Uox. i) study of the physical and chemical properties of the uric acid and its anions; ii) determination of the intrinsic reactivity of the uric acid and its anions with dioxygen; iii) determination of the urate form bound by the enzyme and its reactivity in an active site model. All these studies were carried out at various levels of quantum mechanics, including semi-empirical, DFT and ab initio (HF and MP2) methods. Our study highlights two significant peculiarities of the catalytic mechanism of urate oxidase; i) the substrate bound to the enzyme is the 3-7 urate dianion form, which is not the most stable dianion form in solution but the second most one; ii) the reaction pathway displays a continuous spin change from the reactive state, a triplet state, to the final state, a single state. This spin change occurs without any photon emission but through a degenerescency between the singlet and the triplet states along the first steps of the reaction.
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Muhannad Altarsha. Modélisation du mécanisme catalytique de l'urate oxydase. Autre. Université Henri Poincaré - Nancy 1, 2005. Français. ⟨NNT : 2005NAN10127⟩. ⟨tel-01747493⟩

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