Electronic and geometric structures of the organophosphate-degrading enzyme from <Emphasis Type="Italic">Agrobacterium radiobacter</Emphasis> (OpdA) |
| |
Authors: | Fernanda Ely Kieran S Hadler Nataša Mitić Lawrence R Gahan David L Ollis Nicholas M Plugis Marie T Russo James A Larrabee Gerhard Schenk |
| |
Institution: | (1) School of Chemistry and Molecular Biosciences, The University of Queensland, St. Lucia, QLD, 4072, Australia;(2) Research School of Chemistry, Australian National University, Canberra, ACT, 0200, Australia;(3) Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT 05753, USA;(4) Department of Chemistry, National University of Ireland, Maynooth, Kildare, Ireland; |
| |
Abstract: | The organophosphate-degrading enzyme from Agrobacterium radiobacter (OpdA) is a highly efficient catalyst for the degradation of pesticides and some nerve agents such as sarin. OpdA requires
two metal ions for catalytic activity, and hydrolysis is initiated by a nucleophilic hydroxide that is bound to one of these
metal ions. The precise location of this nucleophile has been contentious, with both a terminal and a metal-ion-bridging hydroxide
as likely candidates. Here, we employed magnetic circular dichroism to probe the electronic and geometric structures of the
Co(II)-reconstituted dinuclear metal center in OpdA. In the resting state the metal ion in the more secluded α site is five-coordinate,
whereas the Co(II) in the solvent-exposed β site is predominantly six-coordinate with two terminal water ligands. Addition
of the slow substrate diethyl 4-methoxyphenyl phosphate does not affect the α site greatly but lowers the coordination number
of the β site to five. A reduction in the exchange coupling constant indicates that substrate binding also triggers a shift
of the μ-hydroxide into a pseudoterminal position in the coordination sphere of either the α or the β metal ion. Mechanistic
implications of these observations are discussed. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|