Nuclear Resonance Vibrational Spectroscopy Definition of O2 Intermediates in an Extradiol Dioxygenase: Correlation to Crystallography and Reactivity
Year: 2018
Type: article
Abstract: The extradiol dioxygenases are a large subclass of mononuclear nonheme Fe enzymes that catalyze the oxidative cleavage of catechols distal to their OH groups. These enzymes are important in bioremediation, and there has been significant interest in understanding how they activate O 2 . The extradiol dioxygenase homoprotocatechuate 2,3-dioxygenase (HPCD) provides an opportunity to study this process, as two O 2 intermediates have been trapped and crystallographically defined using the slow substrate 4-nitrocatechol (4NC): a side-on Fe–O 2 –4NC species and a Fe–O 2 –4NC peroxy bridged species. Also with 4NC, two solution intermediates have been trapped in the H200N variant, where H200 provides a second-sphere hydrogen bond in the wild-type enzyme. While the electronic structure of these solution intermediates has been defined previously as Fe III -superoxo-catecholate and Fe III -peroxy-semiquinone, their geometric structures are unknown. Nuclear resonance vibrational spectroscopy (NRVS) is an important tool for structural definition of nonheme Fe–O 2 intermediates, as all normal modes with Fe displacement have intensity in the NRVS spectrum. In this study, NRVS is used to define the geometric structure of the H200N–4NC solution intermediates in HPCD as an end-on Fe III -superoxo-catecholate and an end-on Fe III -hydroperoxo-semiquinone. Parallel calculations are performed to define the electronic structures and protonation states of the crystallographically defined wild-type HPCD–4NC intermediates, where the side-on intermediate is found to be a Fe III -hydroperoxo-semiquinone. The assignment of this crystallographic intermediate is validated by correlation to the NRVS data through computational removal of H200. While the side-on hydroperoxo semiquinone intermediate is computationally found to be nonreactive in peroxide bridge formation, it is isoenergetic with a superoxo catecholate species that is competent in performing this reaction. This study provides insight into the relative reactivities of Fe III -superoxo and Fe III -hydroperoxo intermediates in nonheme Fe enzymes and into the role H200 plays in facilitating extradiol catalysis.
DOI: 10.1021/jacs.8b06517
Authors: Kyle D. Sutherlin, Yuko Wasada-Tsutsui, Michael M. Mbughuni, Melanie S. Rogers, Kiyoung Park, Lei V. Liu, Yeonju Kwak, Martin Srnec, Lars H. Böttger, Mathieu Frenette, Yoshitaka Yoda, Yasuhiro Kobayashi, Masayuki Kurokuzu, Makina Saito, Makoto Seto, Michael Hu, Jiyong Zhao, E. Ercan Alp, John D. Lipscomb, Edward I. Solomon
Institutions: Stanford University, Nagoya Institute of Technology, University of Minnesota, Japan Synchrotron Radiation Research Institute, Kyoto University, Institute for Integrated Radiation and Nuclear Science, Kyoto University, Argonne National Laboratory, Advanced Photon Source, SLAC National Accelerator Laboratory
Language: English
Subfield: Inorganic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
Awards: Development of Advanced Moessbauer Spectroscopy for Isotope Specific Analysis of Local State, Intermediates in O2 Activation by Oxygenases at Non-heme Iron Centers, G2311276138, G4200735206, Spectroscopic Characterization of Oxygen Intermediates in Non-heme and Heme Iron Enzymes, G6016713957, G786858590
OpenAlex ID: W2901891071