1
|
Bopp CE, Bernet NM, Kohler HPE, Hofstetter TB. Elucidating the Role of O 2 Uncoupling in the Oxidative Biodegradation of Organic Contaminants by Rieske Non-heme Iron Dioxygenases. ACS ENVIRONMENTAL AU 2022; 2:428-440. [PMID: 36164353 PMCID: PMC9502038 DOI: 10.1021/acsenvironau.2c00023] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Oxygenations of aromatic
soil and water contaminants with molecular
O2 catalyzed by Rieske dioxygenases are frequent initial
steps of biodegradation in natural and engineered environments. Many
of these non-heme ferrous iron enzymes are known to be involved in
contaminant metabolism, but the understanding of enzyme–substrate
interactions that lead to successful biodegradation is still elusive.
Here, we studied the mechanisms of O2 activation and substrate
hydroxylation of two nitroarene dioxygenases to evaluate enzyme- and
substrate-specific factors that determine the efficiency of oxygenated
product formation. Experiments in enzyme assays of 2-nitrotoluene
dioxygenase (2NTDO) and nitrobenzene dioxygenase (NBDO) with methyl-,
fluoro-, chloro-, and hydroxy-substituted nitroaromatic substrates
reveal that typically 20–100% of the enzyme’s activity
involves unproductive paths of O2 activation with generation
of reactive oxygen species through so-called O2 uncoupling.
The 18O and 13C kinetic isotope effects of O2 activation and nitroaromatic substrate hydroxylation, respectively,
suggest that O2 uncoupling occurs after generation of FeIII-(hydro)peroxo species in the catalytic cycle. While 2NTDO
hydroxylates ortho-substituted nitroaromatic substrates
more efficiently, NBDO favors meta-substituted, presumably
due to distinct active site residues of the two enzymes. Our data
implies, however, that the O2 uncoupling and hydroxylation
activity cannot be assessed from simple structure–reactivity
relationships. By quantifying O2 uncoupling by Rieske dioxygenases,
our work provides a mechanistic link between contaminant biodegradation,
the generation of reactive oxygen species, and possible adaptation
strategies of microorganisms to the exposure of new contaminants.
Collapse
Affiliation(s)
- Charlotte E. Bopp
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| | - Nora M. Bernet
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Hans-Peter E. Kohler
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Thomas B. Hofstetter
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| |
Collapse
|
2
|
Managing argon interference during measurements of 18O/ 16O ratios in O 2 by continuous-flow isotope ratio mass spectrometry. Anal Bioanal Chem 2022; 414:6177-6186. [PMID: 35841416 PMCID: PMC9314310 DOI: 10.1007/s00216-022-04184-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 06/08/2022] [Accepted: 06/17/2022] [Indexed: 11/08/2022]
Abstract
Abstract Monitoring changes in stable oxygen isotope ratios in molecular oxygen allows for studying many fundamental processes in bio(geo)chemistry and environmental sciences. While the measurement of \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{18}$$\end{document}18O/\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{16}$$\end{document}16O ratios of \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathrm {O}_{2}$$\end{document}O2 in gaseous samples can be carried out conveniently and from extracting moderately small aqueous samples for analyses by continuous-flow isotope ratio mass spectrometry (CF-IRMS), oxygen isotope signatures, \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\updelta ^{18}$$\end{document}δ18O, could be overestimated by more than 6\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\permille$$\end{document}‱ because of interferences from argon in air. Here, we systematically evaluated the extent of such Ar interferences on \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{18}$$\end{document}18O/\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{16}$$\end{document}16O ratios of \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathrm {O}_{2}$$\end{document}O2 for measurements by gas chromatography/IRMS and GasBench/IRMS and propose simple instrumental modifications for improved Ar and \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathrm {O}_{2}$$\end{document}O2 separation as well as post-measurement correction procedures for obtaining accurate \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\updelta ^{18}$$\end{document}δ18O. We subsequently evaluated the consequences of Ar interferences for the quantification of O isotope fractionation in terms of isotope enrichment factors, \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\upepsilon _{\mathrm {O}}$$\end{document}ϵO, and \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{18}$$\end{document}18O kinetic isotope effects (\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{18}$$\end{document}18O KIEs) in samples where \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathrm {O}_{2}$$\end{document}O2 is consumed and Ar:\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathrm {O}_{2}$$\end{document}O2 ratios increase steadily and substantially over the course of a reaction. We show that the extent of O isotope fractionation is overestimated only slightly and that this effect is typically smaller than uncertainties originating from the precision of \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\updelta ^{18}$$\end{document}δ18O measurements and experimental variability. Ar interferences can become more relevant and bias \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\upepsilon _{\mathrm {O}}$$\end{document}ϵO values by more than \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$2\permille$$\end{document}2‱ in aqueous samples where fractional \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathrm {O}_{2}$$\end{document}O2 conversion exceeds 90%. Practically, however, such samples would typically contain less than 25 \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\upmu$$\end{document}μM of \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$\mathrm {O}_{2}$$\end{document}O2 at ambient temperature, an amount that is close to the method detection limit of \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{18}$$\end{document}18O/\documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$$^{16}$$\end{document}16O ratio measurement by CF-IRMS. Graphical abstract ![]()
Supplementary Information The online version contains supplementary material available at 10.1007/s00216-022-04184-3.
Collapse
|
3
|
Pati SG, Bopp CE, Kohler HPE, Hofstetter TB. Substrate-Specific Coupling of O 2 Activation to Hydroxylations of Aromatic Compounds by Rieske Non-heme Iron Dioxygenases. ACS Catal 2022; 12:6444-6456. [PMID: 35692249 PMCID: PMC9171724 DOI: 10.1021/acscatal.2c00383] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 04/09/2022] [Indexed: 02/07/2023]
Abstract
![]()
Rieske dioxygenases
catalyze the initial steps in the hydroxylation
of aromatic compounds and are critical for the metabolism of xenobiotic
substances. Because substrates do not bind to the mononuclear non-heme
FeII center, elementary steps leading to O2 activation
and substrate hydroxylation are difficult to delineate, thus making
it challenging to rationalize divergent observations on enzyme mechanisms,
reactivity, and substrate specificity. Here, we show for nitrobenzene
dioxygenase, a Rieske dioxygenase capable of transforming nitroarenes
to nitrite and substituted catechols, that unproductive O2 activation with the release of the unreacted substrate and reactive
oxygen species represents an important path in the catalytic cycle.
Through correlation of O2 uncoupling for a series of substituted
nitroaromatic compounds with 18O and 13C kinetic
isotope effects of dissolved O2 and aromatic substrates,
respectively, we show that O2 uncoupling occurs after the
rate-limiting formation of FeIII-(hydro)peroxo species
from which substrates are hydroxylated. Substituent effects on the
extent of O2 uncoupling suggest that the positioning of
the substrate in the active site rather than the susceptibility of
the substrate for attack by electrophilic oxygen species is responsible
for unproductive O2 uncoupling. The proposed catalytic
cycle provides a mechanistic basis for assessing the very different
efficiencies of substrate hydroxylation vs unproductive O2 activation and generation of reactive oxygen species in reactions
catalyzed by Rieske dioxygenases.
Collapse
Affiliation(s)
- Sarah G. Pati
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| | - Charlotte E. Bopp
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| | - Hans-Peter E. Kohler
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Thomas B. Hofstetter
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, 8092 Zürich, Switzerland
| |
Collapse
|
4
|
Synthesis, characterization and antimicrobial properties of mononuclear copper(II) compounds of N,N′-di(quinolin-8-yl)cyclohexane-1,2-diamine. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2019.119020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
|
5
|
Qiao J, Ma L, Roth J, Li Y, Liu Y. Kinetic basis for the activation of human cyclooxygenase-2 rather than cyclooxygenase-1 by nitric oxide. Org Biomol Chem 2019; 16:765-770. [PMID: 29308820 DOI: 10.1039/c7ob02992f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Numerous studies have shown that nitric oxide (NO) interacts with human cyclooxygenase (COX); however, conflicting results exist with respect to their interactions. Herein, recombinant human COX-1 and COX-2 were prepared and treated with NO donors individually under anaerobic and aerobic conditions. The S-nitrosylation detection and subsequent kinetic investigations into the arachidonic acid (AA) oxidation of COX enzymes indicate that NO S-nitrosylates both COX-1 and COX-2 in an oxygen-dependent manner, but enhances only the dioxygenase activity of COX-2. The solution viscosity, deuterium kinetic isotope effect (KIE), and oxygen-18 KIE experiments further demonstrate that NO activates COX-2 by altering the protein conformation to stimulate substrate association/product release and by accelerating the rate of hydrogen abstraction from AA by catalytic tyrosine radicals. These novel findings provide useful information for designing new drugs with less cardiotoxic effects that can block the interaction between NO and COX.
Collapse
Affiliation(s)
- Jie Qiao
- Hubei Collaborative Innovation Center for Green Transformation of Bio-resources, Hubei Key Laboratory of Industrial Biotechnology, College of Life Science, Hubei University, Wuhan, Hubei 430062, China.
| | | | | | | | | |
Collapse
|
6
|
Gaule TG, Smith MA, Tych KM, Pirrat P, Trinh CH, Pearson AR, Knowles PF, McPherson MJ. Oxygen Activation Switch in the Copper Amine Oxidase of Escherichia coli. Biochemistry 2018; 57:5301-5314. [PMID: 30110143 PMCID: PMC6136094 DOI: 10.1021/acs.biochem.8b00633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Copper amine oxidases (CuAOs) are metalloenzymes that reduce molecular oxygen to hydrogen peroxide during catalytic turnover of primary amines. In addition to Cu2+ in the active site, two peripheral calcium sites, ∼32 Å from the active site, have roles in Escherichia coli amine oxidase (ECAO). The buried Ca2+ (Asp533, Leu534, Asp535, Asp678, and Ala679) is essential for full-length protein production, while the surface Ca2+ (Glu573, Tyr667, Asp670, and Glu672) modulates biogenesis of the 2,4,5-trihydroxyphenylalanine quinone (TPQ) cofactor. The E573Q mutation at the surface site prevents calcium binding and TPQ biogenesis. However, TPQ biogenesis can be restored by a suppressor mutation (I342F) in the proposed oxygen delivery channel to the active site. While supporting TPQ biogenesis (∼60% WTECAO TPQ), I342F/E573Q has almost no amine oxidase activity (∼4.6% WTECAO activity). To understand how these long-range mutations have major effects on TPQ biogenesis and catalysis, we employed ultraviolet-visible spectroscopy, steady-state kinetics, inhibition assays, and X-ray crystallography. We show that the surface metal site controls the equilibrium (disproportionation) of the Cu2+-substrate reduced TPQ (TPQAMQ) Cu+-TPQ semiquinone (TPQSQ) couple. Removal of the calcium ion from this site by chelation or mutagenesis shifts the equilibrium to Cu2+-TPQAMQ or destabilizes Cu+-TPQSQ. Crystal structure analysis shows that TPQ biogenesis is stalled at deprotonation in the Cu2+-tyrosinate state. Our findings support WTECAO using the inner sphere electron transfer mechanism for oxygen reduction during catalysis, and while a Cu+-tyrosyl radical intermediate is not essential for TPQ biogenesis, it is required for efficient biogenesis.
Collapse
Affiliation(s)
- Thembaninkosi G Gaule
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Mark A Smith
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Katarzyna M Tych
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K.,Physik-Department, Lehrstuhl für Biophysik E22 , Technische Universität München , D-85748 Garching , Germany
| | - Pascale Pirrat
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Chi H Trinh
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Arwen R Pearson
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K.,Hamburg Centre of Ultrafast Imaging and Institute for Nanostructure and Solid State Physics , Universität Hamburg , D-22761 Hamburg , Germany
| | - Peter F Knowles
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| | - Michael J McPherson
- Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, Faculty of Biological Sciences , University of Leeds , Leeds LS2 9JT , U.K
| |
Collapse
|
7
|
Spahr S, Cirpka OA, von Gunten U, Hofstetter TB. Formation of N-Nitrosodimethylamine during Chloramination of Secondary and Tertiary Amines: Role of Molecular Oxygen and Radical Intermediates. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:280-290. [PMID: 27958701 DOI: 10.1021/acs.est.6b04780] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
N-Nitrosodimethylamine (NDMA) is a carcinogenic disinfection byproduct from water chloramination. Despite the identification of numerous NDMA precursors, essential parts of the reaction mechanism such as the incorporation of molecular O2 are poorly understood. In laboratory model systems for the chloramination of secondary and tertiary amines, we investigated the kinetics of precursor disappearance and NDMA formation, quantified the stoichiometries of monochloramine (NH2Cl) and aqueous O2 consumption, derived 18O-kinetic isotope effects (18O-KIE) for the reactions of aqueous O2, and studied the impact of radical scavengers on NDMA formation. Although the molar NDMA yields from five N,N-dimethylamine-containing precursors varied between 1.4% and 90%, we observed the stoichiometric removal of one O2 per N,N-dimethylamine group of the precursor indicating that the oxygenation of N atoms did not determine the molar NDMA yield. Small 18O-KIEs between 1.0026 ± 0.0003 and 1.0092 ± 0.0009 found for all precursors as well as completely inhibited NDMA formation in the presence of radical scavengers (ABTS and trolox) imply that O2 reacted with radical species. Our study suggests that aminyl radicals from the oxidation of organic amines by NH2Cl and N-peroxyl radicals from the reaction of aminyl radicals with aqueous O2 are part of the NDMA formation mechanism.
Collapse
Affiliation(s)
- Stephanie Spahr
- Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland
- School of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Federale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
| | - Olaf A Cirpka
- Center for Applied Geoscience, University of Tübingen , D-72074 Tübingen, Germany
| | - Urs von Gunten
- Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland
- School of Architecture, Civil and Environmental Engineering (ENAC), Ecole Polytechnique Federale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich , CH-8092 Zürich, Switzerland
| | - Thomas B Hofstetter
- Eawag, Swiss Federal Institute of Aquatic Science and Technology , CH-8600 Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics, ETH Zürich , CH-8092 Zürich, Switzerland
| |
Collapse
|
8
|
Tcherkez G. The mechanism of Rubisco-catalysed oxygenation. PLANT, CELL & ENVIRONMENT 2016; 39:983-997. [PMID: 26286702 DOI: 10.1111/pce.12629] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/28/2015] [Accepted: 08/09/2015] [Indexed: 06/04/2023]
Abstract
Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the cornerstone of photosynthetic carbon assimilation because it catalyses the fixation of CO2 onto ribulose-1,5-bisphosphate (RuBP). The enzyme also catalyses RuBP oxygenation, thereby evolving phosphoglycolate which is recycled along the photorespiratory pathway. Oxygenation is quantitatively important, because under ordinary gaseous conditions, more than one third of RuBP molecules are oxygenated rather than carboxylated. However, contrary to carboxylation, the chemical mechanism of oxygenation is not well known, and little progress has been made since the early 80s. Here, I review recent experimental data that provide some new insights into the reaction mechanism, and carry out simple calculations of kinetic parameters. Isotope effects suggest that oxygenation is less likely initiated by a redox phenomenon (such as superoxide production) and more likely involves concerted chemical events that imply interactions with protons. A possible energy profile of the reaction is drawn which suggests that the generation of the oxygenated reaction intermediate (peroxide) is irreversible. Possible changes in oxygenation-associated rate constants between Rubisco forms are discussed.
Collapse
Affiliation(s)
- Guillaume Tcherkez
- Research School of Biology, ANU College of Medicine, Biology and Environment, Australian National University, Canberra, 2601, ACT, Australia
| |
Collapse
|
9
|
Pati SG, Bolotin J, Brennwald MS, Kohler HPE, Werner RA, Hofstetter TB. Measurement of oxygen isotope ratios ((18)O/(16)O) of aqueous O2 in small samples by gas chromatography/isotope ratio mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2016; 30:684-690. [PMID: 26864520 DOI: 10.1002/rcm.7481] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 12/11/2015] [Accepted: 12/12/2015] [Indexed: 06/05/2023]
Abstract
RATIONALE Oxygen isotope fractionation of molecular O2 is an important process for the study of aerobic metabolism, photosynthesis, and formation of reactive oxygen species. The latter is of particular interest for investigating the mechanism of enzyme-catalyzed reactions, such as the oxygenation of organic pollutants, which is an important detoxification mechanism. METHODS We developed a simple method to measure the δ(18) O values of dissolved O2 in small samples using automated split injection for gas chromatography coupled to isotope ratio mass spectrometry (GC/IRMS). After creating a N2 headspace, the dissolved O2 partitions from aqueous solution to the headspace, from which it can be injected into the gas chromatograph. RESULTS In aqueous samples of 10 mL and in diluted air samples, we quantified the δ(18) O values at O2 concentrations of 16 μM and 86 μM, respectively. The chromatographic separation of O2 and N2 with a molecular sieve column made it possible to use N2 as the headspace gas for the extraction of dissolved O2 from water. We were therefore able to apply a rigorous δ(18) O blank correction for the quantification of (18) O/(16) O ratios in 20 nmol of injected O2 . CONCLUSIONS The successful quantification of (18) O-kinetic isotope effects associated with enzymatic and chemical reduction of dissolved O2 illustrates how the proposed method can be applied for studying enzymatic O2 activation mechanisms in a variety of (bio)chemical processes.
Collapse
Affiliation(s)
- Sarah G Pati
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600, Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, CH-8092, Zürich, Switzerland
| | - Jakov Bolotin
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600, Dübendorf, Switzerland
| | - Matthias S Brennwald
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600, Dübendorf, Switzerland
| | - Hans-Peter E Kohler
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600, Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, CH-8092, Zürich, Switzerland
| | - Roland A Werner
- Institute of Agricultural Sciences, ETH Zürich, CH-8092, Zürich, Switzerland
| | - Thomas B Hofstetter
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600, Dübendorf, Switzerland
- Institute of Biogeochemistry and Pollutant Dynamics (IBP), ETH Zürich, CH-8092, Zürich, Switzerland
| |
Collapse
|
10
|
Zhu H, Peck SC, Bonnot F, van der Donk WA, Klinman JP. Oxygen-18 Kinetic Isotope Effects of Nonheme Iron Enzymes HEPD and MPnS Support Iron(III) Superoxide as the Hydrogen Abstraction Species. J Am Chem Soc 2015; 137:10448-51. [PMID: 26267117 PMCID: PMC4970508 DOI: 10.1021/jacs.5b03907] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Nonheme
iron oxygenases that carry out four-electron oxidations
of substrate have been proposed to employ iron(III) superoxide species
to initiate this reaction [Paria, S.; Que, L.; Paine, T. K. Angew. Chem. Int. Ed.2011, 50, 11129]. Here we report experimental evidence in support of this
proposal. 18O KIEs were measured for two recently discovered
mononuclear nonheme iron oxygenases: hydroxyethylphosphonate dioxygenase
(HEPD) and methylphosphonate synthase (MPnS). Competitive 18O KIEs measured with deuterated substrates are larger than those
measured with unlabeled substrates, which indicates that C–H
cleavage must occur before an irreversible reductive step at molecular
oxygen. A similar observation was previously used to implicate copper(II)
superoxide in the H-abstraction reactions catalyzed by dopamine β-monooxygenase
[Tian, G. C.; Klinman, J. P. J. Am. Chem. Soc.1993, 115, 8891] and peptidylglycine α-hydroxylating
monooxygenase [Francisco, W. A.; Blackburn, N. J.; Klinman, J. P. Biochemistry2003, 42, 1813].
Collapse
Affiliation(s)
| | - Spencer C Peck
- Howard Hughes Medical Institute and Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | | | - Wilfred A van der Donk
- Howard Hughes Medical Institute and Department of Chemistry, University of Illinois at Urbana-Champaign , 600 South Mathews Avenue, Urbana, Illinois 61801, United States.,Institute for Genomic Biology, University of Illinois at Urbana-Champaign , 1206 West Gregory Drive, Urbana, Illinois 61801, United States
| | | |
Collapse
|
11
|
Shepard EM, Dooley DM. Inhibition and oxygen activation in copper amine oxidases. Acc Chem Res 2015; 48:1218-26. [PMID: 25897668 DOI: 10.1021/ar500460z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Copper-containing amine oxidases (CuAOs) use both copper and 2,4,5-trihydroxyphenylalanine quinone (TPQ) to catalyze the oxidative deamination of primary amines. The CuAO active site is highly conserved and comprised of TPQ and a mononuclear type II copper center that exhibits five-coordinate, distorted square pyramidal coordination geometry with histidine ligands and equatorially and axially bound water in the oxidized, resting state. The active site is buried within the protein, and CuAOs from various sources display remarkable diversity with respect to the composition of the active site channel and cofactor accessibility. Structural and mechanistic factors that influence substrate preference and inhibitor sensitivity and selectivity have been defined. This Account summarizes the strategies used to design selective CuAO inhibitors based on active site channel characteristics, leading to either enhanced steric fits or the trapping of reactive electrophilic products. These findings provide a framework to support the future development of candidate molecules aimed at minimizing the negative side effects associated with drugs containing amine functionalities. This is vital given the existence of human diamine oxidase and vascular adhesion protein-1, which have distinct amine substrate preferences and are associated with different metabolic processes. Inhibition of these enzymes by antifungal or antiprotozoal agents, as well as classic monoamine oxidase (MAO) inhibitors, may contribute to the adverse side effects associated with drug treatment. These observations provide a rationale for the limited clinical value associated with certain amine-containing pharmaceuticals and emphasize the need for more selective AO inhibitors. This Account also discusses the novel roles of copper and TPQ in the chemistry of O2 activation and substrate oxidation. Reduced CuAOs exist in a redox equilibrium between the Cu(II)-TPQAMQ (aminoquinol) and Cu(I)-TPQSQ (semiquinone). Elucidating the roles of Cu(I), TPQSQ, and TPQAMQ in O2 activation, for example, distinguishing inner-sphere versus outer-sphere electron transfer mechanisms, has been actively investigated since the discovery of TPQSQ in 1991 and has only recently been clarified. Kinetics and spectroscopic studies encompassing metal substitution, stopped-flow and temperature-jump relaxation methods, and oxygen kinetic isotope experiments have provided strong support for an inner-sphere electron transfer step from Cu(I) to O2. Data for two enzymes support a mechanism wherein O2 prebinds to a three-coordinate Cu(I) site, yielding a [Cu(II)(η(1)-O2(-1))](+) intermediate, with H2O2 generated from ensuing rate-determining proton coupled electron transfer from TPQSQ. While kinetics data from the cobalt-substituted yeast enzyme indicated that O2 is reduced through an outer-sphere process involving TPQAMQ, new findings with a bacterial CuAO demonstrate that both the Cu(II) and Co(II) forms of the enzyme operate via parallel mechanisms involving metal-superoxide intermediates. Structural observations of a coordinated TPQSQ-Cu(I) complex in two CuAOs supports previous indications that Cu(II)/(I) ligand substitution chemistry may be mechanistically relevant. Substantial evidence indicates that rapid and reversible inner-sphere reduction of O2 at a three-coordinate Cu(I) site occurs, but the existence of a coordinated semiquinone in some AOs suggests that, in these enzymes, an outer-sphere reaction between O2 and TPQSQ may also be possible, since this is expected to be energetically favorable compared with outer-sphere electron transfer from TPQAMQ to O2.
Collapse
Affiliation(s)
- Eric M. Shepard
- Department
of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - David M. Dooley
- Office
of the President, University of Rhode Island, Kingston, Rhode Island 02881, United States
| |
Collapse
|
12
|
Saucedo-Vázquez JP, Kroneck PMH, Sosa-Torres ME. The role of molecular oxygen in the iron(iii)-promoted oxidative dehydrogenation of amines. Dalton Trans 2015; 44:5510-9. [DOI: 10.1039/c4dt03606a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mechanistic study is presented of the oxidative dehydrogenation of the iron(iii) complex [FeIIIL3]3+, 1, (L3 = 1,9-bis(2′-pyridyl)-5-[(ethoxy-2′′-pyridyl)methyl]-2,5,8-triazanonane) in ethanol in the presence of molecular oxygen.
Collapse
Affiliation(s)
- Juan Pablo Saucedo-Vázquez
- Departamento de Química Inorgánica y Nuclear
- Facultad de Química
- Universidad Nacional Autónoma de México
- Ciudad Universitaria
- México, D.F. 04510
| | | | - Martha Elena Sosa-Torres
- Departamento de Química Inorgánica y Nuclear
- Facultad de Química
- Universidad Nacional Autónoma de México
- Ciudad Universitaria
- México, D.F. 04510
| |
Collapse
|
13
|
Hangasky JA, Gandhi H, Valliere MA, Ostrom NE, Knapp MJ. The rate-limiting step of O2 activation in the α-ketoglutarate oxygenase factor inhibiting hypoxia inducible factor. Biochemistry 2014; 53:8077-84. [PMID: 25423620 PMCID: PMC4283935 DOI: 10.1021/bi501246v] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
![]()
Factor
inhibiting HIF (FIH) is a cellular O2-sensing enzyme, which
hydroxylates the hypoxia inducible factor-1α. Previously reported
inverse solvent kinetic isotope effects indicated that FIH limits
its overall turnover through an O2 activation step (HangaskyJ. A., SabanE.,
and KnappM. J. (2013) Biochemistry52, 1594−160223351038). Here we characterize the rate-limiting step for O2 activation by FIH using a suite of mechanistic probes on
the second order rate constant kcat/KM(O2). Steady-state kinetics showed
that the rate constant for O2 activation was slow (kcat/KM(O2)app = 3500 M–1 s–1) compared with other non-heme iron oxygenases,
and solvent viscosity assays further excluded diffusional encounter
with O2 from being rate limiting on kcat/KM(O2). Competitive
oxygen-18 kinetic isotope effect measurements (18kcat/KM(O2) = 1.0114(5)) indicated that the transition state for O2 activation resembled a cyclic peroxohemiketal, which precedes the
formation of the ferryl intermediate observed in related enzymes.
We interpret this data to indicate that FIH limits its overall activity
at the point of the nucleophilic attack of Fe-bound O2— on the C-2 carbon of αKG. Overall, these results
show that FIH follows the consensus mechanism for αKG oxygenases,
suggesting that FIH may be an ideal enzyme to directly access steps
involved in O2 activation among the broad family of αKG
oxygenases.
Collapse
Affiliation(s)
- John A Hangasky
- Department of Chemistry, University of Massachusetts , Amherst, Massachusetts 01003, United States
| | | | | | | | | |
Collapse
|
14
|
Theodorou V, Skobridis K, Alivertis D, Gerothanassis IP. Synthetic methodologies in organic chemistry involving incorporation of [¹⁷O] and [¹⁸O] isotopes. J Labelled Comp Radiopharm 2014; 57:481-508. [PMID: 24996002 DOI: 10.1002/jlcr.3212] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2014] [Revised: 04/06/2014] [Accepted: 05/15/2014] [Indexed: 11/09/2022]
Abstract
This review is a critical survey of the literature that aims to highlight the most significant developments on synthetic strategies involving stable oxygen isotopes ([(17)O] and [(18)O]). The labeling methodologies are categorized in groups, according to the oxygen-containing functional group.
Collapse
Affiliation(s)
- Vassiliki Theodorou
- Section of Organic Chemistry and Biochemistry, Department of Chemistry, University of Ioannina, Ioannina, GR-451 10, Greece
| | | | | | | |
Collapse
|
15
|
Cheah MH, Millar AH, Myers RC, Day DA, Roth J, Hillier W, Badger MR. Online oxygen kinetic isotope effects using membrane inlet mass spectrometry can differentiate between oxidases for mechanistic studies and calculation of their contributions to oxygen consumption in whole tissues. Anal Chem 2014; 86:5171-8. [PMID: 24786640 DOI: 10.1021/ac501086n] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The reduction chemistry of molecular oxygen underpins the energy metabolism of multicellular organisms, liberating free energy needed to catalyze a plethora of enzymatic reactions. Measuring the isotope signatures of (16)O and (18)O during O2 reduction can provide insights into both kinetic and equilibrium isotope effects. However, current methods to measure O2 isotope signatures are time-consuming and disruptive. This paper describes the application of membrane inlet mass spectrometry to determine the oxygen isotope discrimination of a range of O2-consuming reactions, providing a rapid and convenient method for determining these values. A survey of oxygenase and oxidase reactions provides new insights into previously uncharacterized amino acid oxidase enzymes. Liquid and gas phase measurements show the ease of assays using this approach for purified enzymes, biological extracts and intact tissues.
Collapse
Affiliation(s)
- Mun Hon Cheah
- Division of Plant Science, Research School of Biology, the Australian National University , Canberra ACT 0200, Australia
| | | | | | | | | | | | | |
Collapse
|
16
|
Francis K, Kohen A. Standards for the reporting of kinetic isotope effects in enzymology. ACTA ACUST UNITED AC 2014. [DOI: 10.1016/j.pisc.2014.02.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
17
|
Tano T, Okubo Y, Kunishita A, Kubo M, Sugimoto H, Fujieda N, Ogura T, Itoh S. Redox Properties of a Mononuclear Copper(II)-Superoxide Complex. Inorg Chem 2013; 52:10431-7. [DOI: 10.1021/ic401261z] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Tetsuro Tano
- Department
of Material and Life Science, Division of Advanced Science
and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Yuri Okubo
- Department
of Material and Life Science, Division of Advanced Science
and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Atsushi Kunishita
- Department
of Material and Life Science, Division of Advanced Science
and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Minoru Kubo
- Research
Institute
of Picobiology, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho,
Ako-gun, Hyogo 678-1297, Japan
| | - Hideki Sugimoto
- Department
of Material and Life Science, Division of Advanced Science
and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Nobutaka Fujieda
- Department
of Material and Life Science, Division of Advanced Science
and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Takashi Ogura
- Research
Institute
of Picobiology, Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho,
Ako-gun, Hyogo 678-1297, Japan
| | - Shinobu Itoh
- Department
of Material and Life Science, Division of Advanced Science
and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| |
Collapse
|
18
|
Cheng GJ, Song LJ, Yang YF, Zhang X, Wiest O, Wu YD. Computational Studies on the Mechanism of the Copper-Catalyzed sp3-CH Cross-Dehydrogenative Coupling Reaction. Chempluschem 2013; 78:943-951. [DOI: 10.1002/cplu.201300117] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Indexed: 11/09/2022]
|
19
|
Liu Y, Mukherjee A, Nahumi N, Ozbil M, Brown D, Angeles-Boza AM, Dooley DM, Prabhakar R, Roth JP. Experimental and Computational Evidence of Metal-O2 Activation and Rate-Limiting Proton-Coupled Electron Transfer in a Copper Amine Oxidase. J Phys Chem B 2012; 117:218-29. [DOI: 10.1021/jp3121484] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Yi Liu
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - Arnab Mukherjee
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - Nadav Nahumi
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - Mehmet Ozbil
- Department of Chemistry, University of Miami, 1301 Memorial Drive,
Coral Gables, Florida 33146, United States
| | - Doreen Brown
- Department of Chemistry
and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Alfredo M. Angeles-Boza
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| | - David M. Dooley
- Department of Chemistry
and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Rajeev Prabhakar
- Department of Chemistry, University of Miami, 1301 Memorial Drive,
Coral Gables, Florida 33146, United States
| | - Justine P. Roth
- Department of Chemistry, Johns Hopkins University, 3400 North
Charles Street, Baltimore, Maryland 21218, United States
| |
Collapse
|
20
|
Cooke HA, Peck SC, Evans BS, van der Donk WA. Mechanistic investigation of methylphosphonate synthase, a non-heme iron-dependent oxygenase. J Am Chem Soc 2012; 134:15660-3. [PMID: 22957470 PMCID: PMC3458437 DOI: 10.1021/ja306777w] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Methylphosphonate synthase is a non-heme iron-dependent
oxygenase
that converts 2-hydroxyethylphosphonate (2-HEP) to methylphosphonate.
On the basis of experiments with two enantiomers of a substrate analog,
2-hydroxypropylphosphonate, catalysis is proposed to commence with
stereospecific abstraction of the pro-S hydrogen
on C2 of the substrate. Experiments with isotopologues of 2-HEP indicate
stereospecific hydrogen transfer of the pro-R hydrogen
at C2 of the substrate to the methyl group of methylphosphonate. Kinetic
studies with these substrate isotopologues reveal that neither hydrogen
transfer is rate limiting under saturating substrate conditions. A
mechanism is proposed that is consistent with the available data.
Collapse
Affiliation(s)
- Heather A Cooke
- Howard Hughes Medical Institute and Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, United States
| | | | | | | |
Collapse
|
21
|
Kunishita A, Ertem MZ, Okubo Y, Tano T, Sugimoto H, Ohkubo K, Fujieda N, Fukuzumi S, Cramer CJ, Itoh S. Active Site Models for the CuA Site of Peptidylglycine α-Hydroxylating Monooxygenase and Dopamine β-Monooxygenase. Inorg Chem 2012; 51:9465-80. [DOI: 10.1021/ic301272h] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Atsushi Kunishita
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Mehmed Z. Ertem
- Department of Chemistry, Supercomputing
Institute, and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota
55455, United States
| | - Yuri Okubo
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Tetsuro Tano
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Hideki Sugimoto
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Kei Ohkubo
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Nobutaka Fujieda
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Shunichi Fukuzumi
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
- Department
of Bioinspired Science, Ewha Womans University, Seoul 120-750, Korea
| | - Christopher J. Cramer
- Department of Chemistry, Supercomputing
Institute, and Chemical Theory Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota
55455, United States
| | - Shinobu Itoh
- Department of Material and Life
Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| |
Collapse
|
22
|
Ashley DC, Brinkley DW, Roth JP. Oxygen Isotope Effects as Structural and Mechanistic Probes in Inorganic Oxidation Chemistry. Inorg Chem 2010; 49:3661-75. [DOI: 10.1021/ic901778g] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Daniel C. Ashley
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - David W. Brinkley
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Justine P. Roth
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| |
Collapse
|
23
|
Baron R, McCammon JA, Mattevi A. The oxygen-binding vs. oxygen-consuming paradigm in biocatalysis: structural biology and biomolecular simulation. Curr Opin Struct Biol 2009; 19:672-9. [DOI: 10.1016/j.sbi.2009.10.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Accepted: 10/07/2009] [Indexed: 11/28/2022]
|
24
|
McIntyre NR, Lowe EW, Merkler DJ. Imino-oxy acetic acid dealkylation as evidence for an inner-sphere alcohol intermediate in the reaction catalyzed by peptidylglycine alpha-hydroxylating monooxygenase. J Am Chem Soc 2009; 131:10308-19. [PMID: 19569683 DOI: 10.1021/ja902716d] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Peptidylglycine alpha-hydroxylating monooxygenase (PHM, EC 1.14.17.3) catalyzes the stereospecific hydroxylation of a glycyl alpha-carbon in a reaction that requires O(2) and ascorbate. Subsequent dealkylation of the alpha-hydroxyglycine by another enzyme, peptidylamidoglycolate lyase (PAL. EC 4.3.2.5), yields a bioactive amide and glyoxylate. PHM is a noncoupled, type II dicopper monooxygenase which activates O(2) at only a single copper atom, Cu(M). In this study, the PHM mechanism was probed using a non-natural substrate, benzaldehyde imino-oxy acetic acid (BIAA). PHM catalyzes the O-oxidative dealkylation of BIAA to benzaldoxime and glyoxylate with no involvement of PAL. The minimal kinetic mechanism for BIAA was shown to be steady-state ordered using primary deuterium kinetic isotope effects. The (D)(V/K)(APPARENT, BIAA) decreased from 14.7 +/- 1.0 as [O(2)] --> 0 to 1.0 +/- 0.2 as [O(2)] --> infinity suggesting the dissociation rate constant from the PHM x BIAA complex decreases as [O(2)] increases; thereby, reducing the steady-state concentration of [PHM](free). BIAA was further used to differentiate between potential oxidative Cu/O species using a QM/MM reaction coordinate simulation to determine which species could yield product O-dealkylation that matched our experimental data. The results of this study provided compelling evidence for the presence of a covalently linked Cu(II)-alkoxide intermediate with a quartet spin state responsible BIAA oxidation.
Collapse
Affiliation(s)
- Neil R McIntyre
- Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620, USA
| | | | | |
Collapse
|
25
|
Humphreys KJ, Mirica LM, Wang Y, Klinman JP. Galactose oxidase as a model for reactivity at a copper superoxide center. J Am Chem Soc 2009; 131:4657-63. [PMID: 19290629 PMCID: PMC2683747 DOI: 10.1021/ja807963e] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mononuclear copper enzyme, galactose oxidase, has been investigated under steady-state conditions via O(2)-consumption assays using 1-O-methyl-alpha-D-galactopyranoside as the sugar substrate to produce an aldehyde at the C-6 position. The rate-determining step of the oxidative half-reaction was probed through the measurement of substrate and solvent deuterium and O-18 isotope effects on k(cat)/K(m)(O(2)). The reaction conforms to a ping-pong mechanism with the kinetic parameters for the reductive half, k(cat)/K(m)(S) = 8.3 x 10(3) M(-1) s(-1) at 10 degrees C and pH 7.0, comparing favorably to literature values. The oxidative half-reaction yielded a value of k(cat)/K(m)(O(2)) = 2.5 x 10(6) M(-1) s(-1). A substrate deuterium isotope effect of 32 was measured for the k(cat)/K(m)(S), while a smaller, but significant value of 1.6-1.9 was observed on k(cat)/K(m)(O(2)). O-18 isotope effects of 1.0185 with either protiated or deuterated sugar, together with the absence of any solvent isotope effect, lead to the conclusion that hydrogen atom transfer from reduced cofactor to a Cu(II)-superoxo intermediate is fully rate-determining for k(cat)/K(m)(O(2)). The measured O-18 isotope effects provide corroborative evidence for the reactive superoxo species in the dopamine beta-monooxygenase/peptidylglycine alpha-hydroxylating monooxygenase family, as well as providing a frame of reference for copper-superoxo reactivity. The combination of solvent and substrate deuterium isotope effects rules out solvent deuterium exchange into reduced enzyme as the origin of the relatively small substrate deuterium isotope effect on k(cat)/K(m)(O(2)). These data indicate fundamental differences in the hydrogen transfer step from the carbon of substrate vs the oxygen of reduced cofactor during the reductive and oxidative half-reactions of galactose oxidase.
Collapse
Affiliation(s)
- Kristi J. Humphreys
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Liviu M. Mirica
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Yi Wang
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Judith P. Klinman
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Departments of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA
| |
Collapse
|
26
|
Roth JP. Oxygen isotope effects as probes of electron transfer mechanisms and structures of activated O2. Acc Chem Res 2009; 42:399-408. [PMID: 19195996 DOI: 10.1021/ar800169z] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Competitively determined oxygen ((18)O) isotope effects can be powerful probes of chemical and biological transformations involving molecular oxygen as well as superoxide and hydrogen peroxide. They play a complementary role to crystallography and spectroscopy in the study of activated oxygen intermediates by forging a link between electronic/vibrational structure and the bonding that occurs within ground and transition states along the reaction coordinate. Such analyses can be used to assess the plausibility of intermediates and their catalytic relevance in oxidative processes. This Account describes efforts to advance oxygen kinetic isotope effects ((18)O KIEs) and equilibrium isotope effects ((18)O EIEs) as mechanistic probes of reactive, oxygen-derived species. We focus primarily on transition metal mediated oxidations, outlining both advances over the past five years and current limitations of this approach. Computational methods are now being developed to probe transition states and the accompanying kinetic isotope effects. In particular, we describe the importance of using a full-frequency model to accurately predict the magnitudes as well as the temperature dependence of the isotope effects. Earlier studies have used a "cut-off model," which employs only a few isotopic vibrational modes, and such models tend to overestimate (18)O EIEs. Researchers in mechanistic biological inorganic chemistry would like to differentiate "inner-sphere" from "outer-sphere" reactivity of O(2), a designation that describes the extent of the bonding interaction between metal and oxygen in the transition state. Though this problem remains unsolved, we expect that this isotopic approach will help differentiate these processes. For example, comparisons of (18)O KIEs to (18)O EIEs provide benchmarks that allow us to calibrate computationally derived reaction coordinates. Once the physical origins of heavy atom isotope effects are better understood, researchers will be able to apply the competitive isotope fractionation technique to a wide range of pressing problems in small molecule chemistry and biochemistry.
Collapse
Affiliation(s)
- Justine P. Roth
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| |
Collapse
|
27
|
Smirnov VV, Lanci MP, Roth JP. Computational Modeling of Oxygen Isotope Effects on Metal-Mediated O2 Activation at Varying Temperatures. J Phys Chem A 2009; 113:1934-45. [DOI: 10.1021/jp807796c] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Valeriy V. Smirnov
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Michael P. Lanci
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| | - Justine P. Roth
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218
| |
Collapse
|
28
|
Mirica LM, McCusker KP, Munos JW, Liu HW, Klinman JP. 18O kinetic isotope effects in non-heme iron enzymes: probing the nature of Fe/O2 intermediates. J Am Chem Soc 2008; 130:8122-3. [PMID: 18540575 PMCID: PMC2788235 DOI: 10.1021/ja800265s] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Contrasted here are the competitive 18O/16O kinetic isotope effects (18O KIEs) on kcat/Km(O2) for three non-heme iron enzymes that activate O2 at an iron center coordinated by a 2-His-1-carboxylate facial triad: taurine dioxygenase (TauD), (S)-(2)-hydroxypropylphosphonic acid epoxidase (HppE), and 1-aminocyclopropyl-1-carboxylic acid oxidase (ACCO). Measured 18O KIEs of 1.0102 +/- 0.0002 (TauD), 1.0120 +/- 0.0002 (HppE), and 1.0215 +/- 0.0005 (ACCO) suggest the formation in the rate-limiting step of O2 activation of an FeIII-peroxohemiketal, FeIII-OOH, and FeIV O species, respectively. The comparison of the measured 18O KIEs with calculated or experimental 18O equilibrium isotope effects (18O EIEs) provides new insights into the O2 activation through an inner-sphere mechanism at a non-heme iron center.
Collapse
Affiliation(s)
- Liviu M. Mirica
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, California 94720
| | - Kevin P. McCusker
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, California 94720
| | - Jeffrey W. Munos
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| | - Hung-wen Liu
- Division of Medicinal Chemistry, College of Pharmacy, and Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, Texas 78712
| | - Judith P. Klinman
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, California 94720
| |
Collapse
|
29
|
Mukherjee A, Smirnov VV, Lanci MP, Brown DE, Shepard EM, Dooley DM, Roth JP. Inner-sphere mechanism for molecular oxygen reduction catalyzed by copper amine oxidases. J Am Chem Soc 2008; 130:9459-73. [PMID: 18582059 DOI: 10.1021/ja801378f] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Copper and topaquinone (TPQ) containing amine oxidases utilize O2 for the metabolism of biogenic amines while concomitantly generating H2O2 for use by the cell. The mechanism of O2 reduction has been the subject of long-standing debate due to the obscuring influence of a proton-coupled electron transfer between the tyrosine-derived TPQ and copper, a rapidly established equilibrium precluding assignment of the enzyme in its reactive form. Here, we show that substrate-reduced pea seedling amine oxidase (PSAO) exists predominantly in the Cu(I), TPQ semiquinone state. A new mechanistic proposal for O2 reduction is advanced on the basis of thermodynamic considerations together with kinetic studies (at varying pH, temperature, and viscosity), the identification of steady-state intermediates, and the analysis of competitive oxygen kinetic isotope effects, (18)O KIEs, [kcat/KM((16,16)O2)]/[kcat/KM((16,18)O2)]. The (18)O KIE = 1.0136 +/- 0.0013 at pH 7.2 is independent of temperature from 5 degrees C to 47 degrees C and insignificantly changed to 1.0122 +/- 0.0020 upon raising the pH to 9, thus indicating the absence of kinetic complexity. Using density functional methods, the effect is found to be precisely in the range expected for reversible O2 binding to Cu(I) to afford a superoxide, [Cu(II)(eta(1)-O2)(-I)](+), intermediate. Electron transfer from the TPQ semiquinone follows in the first irreversible step to form a peroxide, Cu(II)(eta(1)-O2)(-II), intermediate driving the reduction of O2. The similar (18)O KIEs reported for copper amine oxidases from other sources raise the possibility that all enzymes react by related inner-sphere mechanisms although additional experiments are needed to test this proposal.
Collapse
Affiliation(s)
- Arnab Mukherjee
- Department of Chemistry, Johns Hopkins University, 3400 North Charles St., Baltimore, Maryland 21218, USA
| | | | | | | | | | | | | |
Collapse
|
30
|
Izzet G, Zeitouny J, Akdas-Killig H, Frapart Y, Ménage S, Douziech B, Jabin I, Le Mest Y, Reinaud O. Dioxygen Activation at a Mononuclear Cu(I) Center Embedded in the Calix[6]arene-Tren Core. J Am Chem Soc 2008; 130:9514-23. [DOI: 10.1021/ja8019406] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Guillaume Izzet
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Joceline Zeitouny
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Huriye Akdas-Killig
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Yves Frapart
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Stéphane Ménage
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Bénédicte Douziech
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Ivan Jabin
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Yves Le Mest
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| | - Olivia Reinaud
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, UMR CNRS 8601, Université Paris Descartes (Paris 5), 45 rue des Saints Pères, 75006 Paris, France, Laboratoire de Chimie, Electrochimie Moléculaires et Chimie Analytique, UMR CNRS 6521, Université de Bretagne Occidentale, CS 93837, 6 av. Le Gorgeu, 29238 Brest cedex 3, France, Service de Chimie Organique, Université Libre de Bruxelles (U.L.B.), Avenue F. D. Roosevelt 50, CP160/06, B-1050 Brussels, Belgium, and Laboratoire de Chimie et
| |
Collapse
|
31
|
de la Lande A, Parisel O, Gérard H, Moliner V, Reinaud O. Theoretical Exploration of the Oxidative Properties of a [(trenMe1)CuO2]+Adduct Relevant to Copper Monooxygenase Enzymes: Insights into Competitive Dehydrogenation versus Hydroxylation Reaction Pathways. Chemistry 2008; 14:6465-73. [DOI: 10.1002/chem.200701595] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
32
|
Roth JP, Cramer CJ. Direct Examination of H2O2 Activation by a Heme Peroxidase. J Am Chem Soc 2008; 130:7802-3. [DOI: 10.1021/ja802098c] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Justine P. Roth
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore Maryland 21218, and Department of Chemistry and Research Computing Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55410
| | - Christopher J. Cramer
- Department of Chemistry, Johns Hopkins University, 3400 North Charles Street, Baltimore Maryland 21218, and Department of Chemistry and Research Computing Center, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55410
| |
Collapse
|
33
|
The nature of O2 activation by the ethylene-forming enzyme 1-aminocyclopropane-1-carboxylic acid oxidase. Proc Natl Acad Sci U S A 2008; 105:1814-9. [PMID: 18238897 DOI: 10.1073/pnas.0711626105] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ethylene is a plant hormone important in many aspects of plant growth and development such as germination, fruit ripening, and senescence. 1-Aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACCO), an O2-activating ascorbate-dependent nonheme iron enzyme, catalyzes the last step in ethylene biosynthesis. The O2 activation process by ACCO was investigated using steady-state kinetics, solvent isotope effects (SIEs), and competitive oxygen kinetic isotope effects (18O KIEs) to provide insights into the nature of the activated oxygen species formed at the active-site iron center and its dependence on ascorbic acid. The observed large 18O KIE of 1.0215 +/- 0.0005 strongly supports a rate-determining step formation of an Fe(IV) O species, which acts as the reactive intermediate in substrate oxidation. The large SIE on kcat/Km(O2) of 5.0 +/- 0.9 suggests that formation of this Fe(IV) O species is linked to a rate-limiting proton or hydrogen atom transfer step. Based on the observed decrease in SIE and 18O KIE values for ACCO at limiting ascorbate concentrations, ascorbate is proposed to bind in a random manner, depending on its concentration. We conclude that ascorbate is not essential for initial O2 binding and activation but is required for rapid Fe(IV) O formation under catalytic turnover. Similar studies can be performed for other nonheme iron enzymes, with the 18O KIEs providing a kinetic probe into the chemical nature of Fe/O2 intermediates formed in the first irreversible step of the O2 activation.
Collapse
|
34
|
|