Marius Réglier

Molecular structure and catechol oxidase activity of a new copper(I) complex with sterically crowded monodentate N-donor ligand

The attempted alkylation of 1,3-bis(2-pyridylimino)isoindoline (indH) by the use of n-BuLi and subsequent alkyl halides led to quaternization of the pyridine nitrogens and the zwitterionic monodentate N-ligand (Me(2)ind)I was formed. By the use of the ligand the copper(I) complex [Cu(I)(Me(2)ind)I(2)] was prepared and its structure determined. It was found to be good catalyst for the oxidation of 3,5-di-tert-butylcatechol (DTBCH(2)) to 3,5-di-tert-butyl-1,2-benzoquinone (DTBQ) and H(2)O(2) by dioxygen. Detailed kinetic studies revealed first-order dependence on the catalyst and dioxygen concentration and saturation type behavior with respect to the substrate.

CHAPTER 20:1-Aminocyclopropane-1-Carboxylic Acid Oxidase

1-Aminocyclopropane carboxylic acid (ACC) oxidase (ACCO) catalyses the final step in ethylene biosynthesis, a key hormone in plant development, stress responses and defence. The substrate, ACC, is converted into ethylene in the presence of dioxygen and a reductant. ACCO also requires carbon dioxide (or bicarbonate) for activity. The crystal structure of ACCO from Petunia hybrida reveals a core folded into a distorted jelly-roll motif (double-stranded β-helix fold) and an active site composed of a single Fe(ii) coordinated by the side chains of two histidines and one aspartate in a 2-His, 1-Asp facial triad. ACCO is related to the 2-oxoglutarate (2OG)-dependent oxygenases although using carbon dioxide and ascorbate rather than 2OG for activity. The present chapter summarizes the advances towards understanding this intriguing enzyme and current hypotheses on the active conformation of the protein, its interaction with substrates and cofactors, the role of CO2/bicarbonate as a cofactor, and its catalytic mechanism.

ACC-Oxidase like activity of a copper (II)–ACC complex in the presence of hydrogen peroxide. Detection of a reaction intermediate at low temperature

A Cu(II)-ACC complex [(Bpy)Cu(ACC)(H2O)]ClO4 (1) was prepared and its treatment with hydrogen peroxide gave rise to ethylene production in an ACC-Oxidase like activity. A brown species that could be a key intermediate in the reaction was detected at low temperature.