Non-heme iron (NHFe) enzymes are ubiquitous in biology and catalyze a wide range of reactions involving dioxygen. These include mono- and dioxygenation, H-atom abstraction for hydroxylation, halogenation and desaturation and electrophilic aromatic attack. The non-heme enzymes can be divided into classes that use a ferrous center to activate dioxygen and classes that use a ferric site to activate substrate for the spin forbidden reaction with dioxygen. The ferrous enzymes include the pterin and ?-ketoglutarate dependent dioxygenases, the Rieske dioxygenases, the extradiol dioxygenases and the anticancer drug Bleomycin. While the natures of the cosubstrate-FeII interactions that activate O2 are not defined, peroxo and high valent oxo intermediates have been trapped in a number of these enzymes and relevant model complexes of these intermediates exist with abiological ligation. The ferric/substrate activating enzymes are the lipoxygenases and the intradiol dioxygenases. Lipoxygenase is thought to activate substrate by H-atom abstraction while for the intradiol dioxygenases substrate activation is thought to occur through direct coordination to the ferric center. No intermediate has been trapped for either enzyme. The non-heme iron enzymes have generally been challenging to study due to their lack of spectral features. The goals of this research project have been to generate new spectroscopic methods and approaches to study the non-heme iron enzymes. These methods are used to experimentally define substrate and cofactor interactions with the iron sites and the natures of the intermediates and their key geometric and electronic contributions to reactivity. Further these experimental results are strongly coupled with density functional theory (DFT) calculations to define structure/function correlations, to understand how the iron site is activated for reaction by substrate or cofactor binding, and to understand their reaction mechanisms on a molecular level. Spectroscopic methods are also being developed to directly probe iron centers in highly covalent porphyrin environments to understand how heme relates to NHFe in oxygen activation and in factors that control reactivity.

Public Health Relevance

The non-heme iron enzymes are involved in antibiotic, collagen and natural product biosynthesis, the synthesis of signaling agents in asthma and atherosclerosis, bioremediation, reactivities related to cancer treatment (hypoxia, DNA repair and cleavage) and their mutations are associated with a range of genetic diseases (phenylketonuria, tyrosinemia, etc.). This research provides definitive insight into NHFe reactivity and the factors that influence this for understanding diseases on a molecular level and to aid in development of new drugs.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM040392-27
Application #
8646921
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Anderson, Vernon
Project Start
1988-07-01
Project End
2015-04-30
Budget Start
2014-05-01
Budget End
2015-04-30
Support Year
27
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Stanford University
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
City
Stanford
State
CA
Country
United States
Zip Code
94304
Iyer, Shyam R; Chaplin, Vanessa D; Knapp, Michael J et al. (2018) O2 Activation by Nonheme FeII ?-Ketoglutarate-Dependent Enzyme Variants: Elucidating the Role of the Facial Triad Carboxylate in FIH. J Am Chem Soc 140:11777-11783
Sutherlin, Kyle D; Wasada-Tsutsui, Yuko; Mbughuni, Michael M et al. (2018) Nuclear Resonance Vibrational Spectroscopy Definition of O2 Intermediates in an Extradiol Dioxygenase: Correlation to Crystallography and Reactivity. J Am Chem Soc :
Goudarzi, Serra; Babicz Jr, Jeffrey T; Kabil, Omer et al. (2018) Spectroscopic and Electronic Structure Study of ETHE1: Elucidating the Factors Influencing Sulfur Oxidation and Oxygenation in Mononuclear Nonheme Iron Enzymes. J Am Chem Soc 140:14887-14902
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Kjær, Kasper S; Zhang, Wenkai; Alonso-Mori, Roberto et al. (2017) Ligand manipulation of charge transfer excited state relaxation and spin crossover in [Fe(2,2'-bipyridine)2(CN)2]. Struct Dyn 4:044030
Titus, Charles J; Baker, Michael L; Lee, Sang Jun et al. (2017) L-edge spectroscopy of dilute, radiation-sensitive systems using a transition-edge-sensor array. J Chem Phys 147:214201
Sharma, Savita K; Schaefer, Andrew W; Lim, Hyeongtaek et al. (2017) A Six-Coordinate Peroxynitrite Low-Spin Iron(III) Porphyrinate Complex-The Product of the Reaction of Nitrogen Monoxide (·NO(g)) with a Ferric-Superoxide Species. J Am Chem Soc 139:17421-17430

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