title: Investigation of the hydroxylation mechanism of noncoupled copper oxygenases by ab initio molecular dynamics simulations.
abstract: In Nature, the family of copper monooxygenases comprised of peptidylglycine α-hydroxylating monooxygenase (PHM), dopamine β-monooxygenase (DβM), and tyramine β-monooxygenase (TβM) is known to perform dioxygen-dependent hydroxylation of aliphatic C-H bonds by using two uncoupled metal sites. In spite of many investigations, including biochemical, chemical, and computational, details of the C-H bond oxygenation mechanism remain elusive. Herein we report an investigation of the mechanism of hydroxylation by PHM by using hybrid quantum/classical potentials (i.e., QM/MM). Although previous investigations using hybrid QM/MM techniques were restricted to geometry optimizations, we have carried out ab initio molecular dynamics simulations in order to include the intrinsic flexibility of the active sites in the modeling protocol. The major finding of this study is an extremely fast rebound step after the initial hydrogen-abstraction step promoted by the cupric-superoxide adduct. The hydrogen-abstraction/rebound sequence leads to the formation of an alkyl hydroperoxide intermediate. Long-range electron transfer from the remote copper site subsequently triggers its reduction to the hydroxylated substrate. We finally show two reactivity consequences inherent in the new mechanistic proposal, the investigation of which would provide a means to check its validity by experimental means.
authors.affiliation: Departament de Química Física i Analítica, Universitat Jaume I, 12071 Castellón (Spain), Fax: (+34) 964-345654.
authors.forename: Conchín
authors.initials: C
authors.lastname: Meliá
authors.forename: Silvia
authors.initials: S
authors.lastname: Ferrer
authors.forename: Jan
authors.initials: J
authors.lastname: Řezáč
authors.forename: Olivier
authors.initials: O
authors.lastname: Parisel
authors.forename: Olivia
authors.initials: O
authors.lastname: Reinaud
authors.forename: Vicent
authors.initials: V
authors.lastname: Moliner
authors.forename: Aurélien
authors.initials: A
authors.lastname: de la Lande
mesh_terms: D020134:Catalytic Domain; D004299:Dopamine beta-Hydroxylase / Q000737:chemistry / Q000378:metabolism; D004579:Electron Transport; D006859:Hydrogen / Q000737:chemistry / Q000378:metabolism; D006900:Hydroxylation; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D011789:Quantum Theory
chemical_list: D009097:Multienzyme Complexes; D006859:Hydrogen; D006899:Mixed Function Oxygenases; C023205:tyramine beta-hydroxylase; D004299:Dopamine beta-Hydroxylase; C035189:peptidylglycine monooxygenase
keywords: ab initio calculations; copper; electron transfer; enzymes; molecular dynamics; reaction mechanisms