1
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Hoog TG, Pawlak MR, Gaut NJ, Baxter GC, Bethel TA, Adamala KP, Engelhart AE. Emergent ribozyme behaviors in oxychlorine brines indicate a unique niche for molecular evolution on Mars. Nat Commun 2024; 15:3863. [PMID: 38769315 PMCID: PMC11106070 DOI: 10.1038/s41467-024-48037-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Accepted: 04/19/2024] [Indexed: 05/22/2024] Open
Abstract
Mars is a particularly attractive candidate among known astronomical objects to potentially host life. Results from space exploration missions have provided insights into Martian geochemistry that indicate oxychlorine species, particularly perchlorate, are ubiquitous features of the Martian geochemical landscape. Perchlorate presents potential obstacles for known forms of life due to its toxicity. However, it can also provide potential benefits, such as producing brines by deliquescence, like those thought to exist on present-day Mars. Here we show perchlorate brines support folding and catalysis of functional RNAs, while inactivating representative protein enzymes. Additionally, we show perchlorate and other oxychlorine species enable ribozyme functions, including homeostasis-like regulatory behavior and ribozyme-catalyzed chlorination of organic molecules. We suggest nucleic acids are uniquely well-suited to hypersaline Martian environments. Furthermore, Martian near- or subsurface oxychlorine brines, and brines found in potential lifeforms, could provide a unique niche for biomolecular evolution.
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Affiliation(s)
- Tanner G Hoog
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA
| | - Matthew R Pawlak
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 321 Church Street SE, Minneapolis, MN, 55455, USA
| | - Nathaniel J Gaut
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 321 Church Street SE, Minneapolis, MN, 55455, USA
| | - Gloria C Baxter
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA
| | - Thomas A Bethel
- Department of Ecology, Evolution, and Behavior, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Avenue, St. Paul, MN, 55108, USA
| | - Katarzyna P Adamala
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 321 Church Street SE, Minneapolis, MN, 55455, USA
| | - Aaron E Engelhart
- Department of Genetics, Cell Biology, and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, MN, 55455, USA.
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, 321 Church Street SE, Minneapolis, MN, 55455, USA.
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2
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Schmidt D, Falb N, Serra I, Bellei M, Pfanzagl V, Hofbauer S, Van Doorslaer S, Battistuzzi G, Furtmüller PG, Obinger C. Compound I Formation and Reactivity in Dimeric Chlorite Dismutase: Impact of pH and the Dynamics of the Catalytic Arginine. Biochemistry 2023; 62:835-850. [PMID: 36706455 PMCID: PMC9910045 DOI: 10.1021/acs.biochem.2c00696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/02/2023] [Indexed: 01/28/2023]
Abstract
The heme enzyme chlorite dismutase (Cld) catalyzes the degradation of chlorite to chloride and dioxygen. Many questions about the molecular reaction mechanism of this iron protein have remained unanswered, including the electronic nature of the catalytically relevant oxoiron(IV) intermediate and its interaction with the distal, flexible, and catalytically active arginine. Here, we have investigated the dimeric Cld from Cyanothece sp. PCC7425 (CCld) and two variants having the catalytic arginine R127 (i) hydrogen-bonded to glutamine Q74 (wild-type CCld), (ii) arrested in a salt bridge with a glutamate (Q74E), or (iii) being fully flexible (Q74V). Presented stopped-flow spectroscopic studies demonstrate the initial and transient appearance of Compound I in the reaction between CCld and chlorite at pH 5.0 and 7.0 and the dominance of spectral features of an oxoiron(IV) species (418, 528, and 551 nm) during most of the chlorite degradation period at neutral and alkaline pH. Arresting the R127 in a salt bridge delays chlorite decomposition, whereas increased flexibility accelerates the reaction. The dynamics of R127 does not affect the formation of Compound I mediated by hypochlorite but has an influence on Compound I stability, which decreases rapidly with increasing pH. The decrease in activity is accompanied by the formation of protein-based amino acid radicals. Compound I is demonstrated to oxidize iodide, chlorite, and serotonin but not hypochlorite. Serotonin is able to dampen oxidative damage and inactivation of CCld at neutral and alkaline pH. Presented data are discussed with respect to the molecular mechanism of Cld and the pronounced pH dependence of chlorite degradation.
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Affiliation(s)
- Daniel Schmidt
- Institute
of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190Vienna, Austria
| | - Nikolaus Falb
- Institute
of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190Vienna, Austria
| | - Ilenia Serra
- BIMEF
Laboratory, Department of Chemistry, University
of Antwerp, 2000Antwerp, Belgium
| | - Marzia Bellei
- Department
of Life Sciences, University of Modena and
Reggio Emilia, 41100Modena, Italy
| | - Vera Pfanzagl
- Institute
of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190Vienna, Austria
| | - Stefan Hofbauer
- Institute
of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190Vienna, Austria
| | - Sabine Van Doorslaer
- BIMEF
Laboratory, Department of Chemistry, University
of Antwerp, 2000Antwerp, Belgium
| | - Gianantonio Battistuzzi
- Department
of Chemistry and Geology, University of
Modena and Reggio Emilia, 41100Modena, Italy
| | - Paul G. Furtmüller
- Institute
of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190Vienna, Austria
| | - Christian Obinger
- Institute
of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Muthgasse 18, A-1190Vienna, Austria
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3
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Geeraerts Z, Stiller OR, Lukat-Rodgers GS, Rodgers KR. Roles of High-Valent Hemes and pH Dependence in Halite Decomposition Catalyzed by Chlorite Dismutase from Dechloromonas aromatica. ACS Catal 2022; 12:8641-8657. [DOI: 10.1021/acscatal.2c01428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Zachary Geeraerts
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Olivia R. Stiller
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Gudrun S. Lukat-Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
| | - Kenton R. Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58108, United States
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4
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Püschmann J, Mahor D, de Geus DC, Strampraad MJF, Srour B, Hagen WR, Todorovic S, Hagedoorn PL. Unique Biradical Intermediate in the Mechanism of the Heme Enzyme Chlorite Dismutase. ACS Catal 2021; 11:14533-14544. [PMID: 34888122 PMCID: PMC8650003 DOI: 10.1021/acscatal.1c03432] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 11/04/2021] [Indexed: 11/30/2022]
Abstract
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The heme enzyme chlorite
dismutase (Cld) catalyzes O–O bond
formation as part of the conversion of the toxic chlorite (ClO2–) to chloride (Cl–) and
molecular oxygen (O2). Enzymatic O–O bond formation
is rare in nature, and therefore, the reaction mechanism of Cld is
of great interest. Microsecond timescale pre-steady-state kinetic
experiments employing Cld from Azospira oryzae (AoCld), the natural substrate chlorite, and the
model substrate peracetic acid (PAA) reveal the formation of distinct
intermediates. AoCld forms a complex with PAA rapidly,
which is cleaved heterolytically to yield Compound I, which is sequentially
converted to Compound II. In the presence of chlorite, AoCld forms an initial intermediate with spectroscopic characteristics
of a 6-coordinate high-spin ferric substrate adduct, which subsequently
transforms at kobs = 2–5 ×
104 s–1 to an intermediate 5-coordinated
high-spin ferric species. Microsecond-timescale freeze-hyperquench
experiments uncovered the presence of a transient low-spin ferric
species and a triplet species attributed to two weakly coupled amino
acid cation radicals. The intermediates of the chlorite reaction were
not observed with the model substrate PAA. These findings demonstrate
the nature of physiologically relevant catalytic intermediates and
show that the commonly used model substrate may not behave as expected,
which demands a revision of the currently proposed mechanism of Clds.
The transient triplet-state biradical species that we designate as
Compound T is, to the best of our knowledge, unique in heme enzymology.
The results highlight electron paramagnetic resonance spectroscopic
evidence for transient intermediate formation during the reaction
of AoCld with its natural substrate chlorite. In
the proposed mechanism, the heme iron remains ferric throughout the
catalytic cycle, which may minimize the heme moiety’s reorganization
and thereby maximize the enzyme’s catalytic efficiency.
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Affiliation(s)
- Julia Püschmann
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Durga Mahor
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Daniël C. de Geus
- Janssen Vaccines & Prevention, Archimedesweg 4-6, 2333 CN Leiden, The Netherlands
| | - Marc J. F. Strampraad
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Batoul Srour
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Wilfred R. Hagen
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
| | - Smilja Todorovic
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade NOVA de Lisboa, Av. da República, 2780-157 Oeiras, Portugal
| | - Peter-Leon Hagedoorn
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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5
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Milazzo L, Gabler T, Pühringer D, Jandova Z, Maresch D, Michlits H, Pfanzagl V, Djinović-Carugo K, Oostenbrink C, Furtmüller PG, Obinger C, Smulevich G, Hofbauer S. Redox Cofactor Rotates during Its Stepwise Decarboxylation: Molecular Mechanism of Conversion of Coproheme to Heme b. ACS Catal 2019; 9:6766-6782. [PMID: 31423350 PMCID: PMC6691569 DOI: 10.1021/acscatal.9b00963] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 05/20/2019] [Indexed: 12/24/2022]
Abstract
Coproheme decarboxylase (ChdC) catalyzes the last step in the heme biosynthesis pathway of monoderm bacteria with coproheme acting both as redox cofactor and substrate. Hydrogen peroxide mediates the stepwise decarboxylation of propionates 2 and 4 of coproheme. Here we present the crystal structures of coproheme-loaded ChdC from Listeria monocytogenes (LmChdC) and the three-propionate intermediate, for which the propionate at position 2 (p2) has been converted to a vinyl group and is rotated by 90° compared to the coproheme complex structure. Single, double, and triple mutants of LmChdC, in which H-bonding interactions to propionates 2, 4, 6, and 7 were eliminated, allowed us to obtain the assignment of the coproheme propionates by resonance Raman spectroscopy and to follow the H2O2-mediated conversion of coproheme to heme b. Substitution of H2O2 by chlorite allowed us to monitor compound I formation in the inactive Y147H variant which lacks the catalytically essential Y147. This residue was demonstrated to be oxidized during turnover by using the spin-trap 2-methyl-2-nitrosopropane. Based on these findings and the data derived from molecular dynamics simulations of cofactor structures in distinct poses, we propose a reaction mechanism for the stepwise decarboxylation of coproheme that includes a 90° rotation of the intermediate three-propionate redox cofactor.
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Affiliation(s)
- Lisa Milazzo
- Dipartimento
di Chimica “Ugo Schiff”, Università
di Firenze, Via della
Lastruccia 3-13, I-50019 Sesto Fiorentino (FI), Italy
| | - Thomas Gabler
- Department
of Chemistry, Division of Biochemistry, BOKU−University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Dominic Pühringer
- Department
for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
| | - Zuzana Jandova
- Department
of Material Sciences and Process Engineering, Institute of Molecular
Modeling and Simulation, BOKU−University
of Natural Resources and Life Sciences, A-1190 Vienna, Austria
| | - Daniel Maresch
- Department
of Chemistry, Division of Biochemistry, BOKU−University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Hanna Michlits
- Department
of Chemistry, Division of Biochemistry, BOKU−University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Vera Pfanzagl
- Department
of Chemistry, Division of Biochemistry, BOKU−University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Kristina Djinović-Carugo
- Department
for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
- Department
of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Chris Oostenbrink
- Department
of Material Sciences and Process Engineering, Institute of Molecular
Modeling and Simulation, BOKU−University
of Natural Resources and Life Sciences, A-1190 Vienna, Austria
| | - Paul G. Furtmüller
- Department
of Chemistry, Division of Biochemistry, BOKU−University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Christian Obinger
- Department
of Chemistry, Division of Biochemistry, BOKU−University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Giulietta Smulevich
- Dipartimento
di Chimica “Ugo Schiff”, Università
di Firenze, Via della
Lastruccia 3-13, I-50019 Sesto Fiorentino (FI), Italy
| | - Stefan Hofbauer
- Department
of Chemistry, Division of Biochemistry, BOKU−University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
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6
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Schaffner I, Mlynek G, Flego N, Pühringer D, Libiseller-Egger J, Coates L, Hofbauer S, Bellei M, Furtmüller PG, Battistuzzi G, Smulevich G, Djinović-Carugo K, Obinger C. Molecular Mechanism of Enzymatic Chlorite Detoxification: Insights from Structural and Kinetic Studies. ACS Catal 2017; 7:7962-7976. [PMID: 29142780 PMCID: PMC5678291 DOI: 10.1021/acscatal.7b01749] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Revised: 09/22/2017] [Indexed: 01/19/2023]
Abstract
![]()
The
heme enzyme chlorite dismutase (Cld) catalyzes the degradation
of chlorite to chloride and dioxygen. Although structure and steady-state
kinetics of Clds have been elucidated, many questions remain (e.g.,
the mechanism of chlorite cleavage and the pH dependence of the reaction).
Here, we present high-resolution X-ray crystal structures of a dimeric
Cld at pH 6.5 and 8.5, its fluoride and isothiocyanate complexes and
the neutron structure at pH 9.0 together with the pH dependence of
the Fe(III)/Fe(II) couple, and the UV–vis and resonance Raman
spectral features. We demonstrate that the distal Arg127 cannot act
as proton acceptor and is fully ionized even at pH 9.0 ruling out
its proposed role in dictating the pH dependence of chlorite degradation.
Stopped-flow studies show that (i) Compound I and hypochlorite do
not recombine and (ii) Compound II is the immediately formed redox
intermediate that dominates during turnover. Homolytic cleavage of
chlorite is proposed.
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Affiliation(s)
- Irene Schaffner
- Department
of Chemistry, Division of Biochemistry, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Georg Mlynek
- Department
for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Dr.-Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Nicola Flego
- Dipartimento
di Chimica “Ugo Schiff”, Università di Firenze, Via della
Lastruccia 3-13, I-50019 Sesto Fiorentino (FI), Italy
| | - Dominic Pühringer
- Department
for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Dr.-Bohr-Gasse 9, A-1030 Vienna, Austria
| | - Julian Libiseller-Egger
- Department
of Chemistry, Division of Biochemistry, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Leighton Coates
- Biology
and Soft Matter Division, Oak Ridge National Laboratory, 1 Bethel
Valley Road, Oak Ridge, Tennessee 37831, United States
| | - Stefan Hofbauer
- Department
of Chemistry, Division of Biochemistry, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Marzia Bellei
- Department
of Life Sciences, University of Modena and Reggio Emilia, Via Campi
103, 41125 Modena, Italy
| | - Paul G. Furtmüller
- Department
of Chemistry, Division of Biochemistry, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Gianantonio Battistuzzi
- Department
of Chemistry and Geology, University of Modena and Reggio Emilia, Via Campi 103, 41125 Modena, Italy
| | - Giulietta Smulevich
- Dipartimento
di Chimica “Ugo Schiff”, Università di Firenze, Via della
Lastruccia 3-13, I-50019 Sesto Fiorentino (FI), Italy
| | - Kristina Djinović-Carugo
- Department
for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Dr.-Bohr-Gasse 9, A-1030 Vienna, Austria
- Department
of Biochemistry, Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000 Ljubljana, Slovenia
| | - Christian Obinger
- Department
of Chemistry, Division of Biochemistry, BOKU—University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
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7
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Bischin C, Mot A, Stefancu A, Leopold N, Hathazi D, Damian G, Silaghi-Dumitrescu R. Chlorite reactivity with myoglobin: Analogy with peroxide and nitrite chemistry? J Inorg Biochem 2017; 172:122-128. [PMID: 28458145 DOI: 10.1016/j.jinorgbio.2017.04.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 04/19/2017] [Accepted: 04/21/2017] [Indexed: 10/19/2022]
Abstract
Stopped-flow UV-vis data allow for the first time direct spectroscopic detection of a ferryl species during the reaction of met myoglobin (Mb) with chlorite, analogous to what is observed in the reaction with peroxides. Ferryl is also observed in the reaction of oxy Mb+chlorite. A pathway involving Fe-O-O-ClO2 is explored by analogy with the Fe-O-O-NO and Fe-O-O-NO2 previously proposed as intermediates in the reactions of oxy globins with nitric oxide and nitrite, respectively. However, Fe-O-O-ClO2 is not detectable in these stopped-flow experiments and is in fact, unlike its nitrogenous congeners, predicted by density functional theory (DFT) to be impossible for a heme complex. Deoxy Mb reacts with chlorite faster than met - suggesting that, unlike with hydrogen peroxide (with which deoxy Mb reacts slower than met), binding of chlorite to the heme is not a rate-determining step (hence, most likely, an outer-sphere electron transfer mechanism); to correlate this, a Fe-O-Cl-O adduct was not observed experimentally for the met or for the deoxy reactions - even though prior DFT calculations suggest it to be feasible and detectable.
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Affiliation(s)
- Cristina Bischin
- Department of Chemistry, Babes-Bolyai University, 11 Arany Janos Street, Cluj-Napoca 400028, Romania
| | - Augustin Mot
- Department of Chemistry, Babes-Bolyai University, 11 Arany Janos Street, Cluj-Napoca 400028, Romania
| | - Andrei Stefancu
- Department of Physics, Babes-Bolyai University, 11 Arany Janos Street, Cluj-Napoca 400028, Romania
| | - Nicolae Leopold
- Department of Physics, Babes-Bolyai University, 11 Arany Janos Street, Cluj-Napoca 400028, Romania
| | - Denisa Hathazi
- Department of Chemistry, Babes-Bolyai University, 11 Arany Janos Street, Cluj-Napoca 400028, Romania
| | - Grigore Damian
- Department of Physics, Babes-Bolyai University, 11 Arany Janos Street, Cluj-Napoca 400028, Romania
| | - Radu Silaghi-Dumitrescu
- Department of Chemistry, Babes-Bolyai University, 11 Arany Janos Street, Cluj-Napoca 400028, Romania.
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8
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Flemmig J, Schlorke D, Kühne FW, Arnhold J. Inhibition of the heme-induced hemolysis of red blood cells by the chlorite-based drug WF10. Free Radic Res 2016; 50:1386-1395. [DOI: 10.1080/10715762.2016.1252838] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- J. Flemmig
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
| | - D. Schlorke
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
| | - F.-W. Kühne
- OXO Chemie (Thailand) Co., Ltd, Bangkok, Thailand
| | - J. Arnhold
- Institute for Medical Physics and Biophysics, University of Leipzig, Leipzig, Germany
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9
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Reactions of aquacobalamin and cob(II)alamin with chlorite and chlorine dioxide. J Biol Inorg Chem 2016; 22:453-459. [DOI: 10.1007/s00775-016-1417-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 11/14/2016] [Indexed: 10/20/2022]
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10
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Kundrát P, Friedland W. Enhanced release of primary signals may render intercellular signalling ineffective due to spatial aspects. Sci Rep 2016; 6:33214. [PMID: 27645799 PMCID: PMC5028836 DOI: 10.1038/srep33214] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 08/03/2016] [Indexed: 11/30/2022] Open
Abstract
Detailed mechanistic modelling has been performed of the intercellular signalling cascade between precancerous cells and their normal neighbours that leads to a selective removal of the precancerous cells by apoptosis. Two interconnected signalling pathways that were identified experimentally have been modelled, explicitly accounting for temporal and spatial effects. The model predicts highly non-linear behaviour of the signalling. Importantly, under certain conditions, enhanced release of primary signals by precancerous cells renders the signalling ineffective. This counter-intuitive behaviour arises due to spatial aspects of the underlying signalling scheme: Increased primary signalling by precancerous cells does, upon reaction with factors derived from normal cells, produce higher yields of apoptosis-triggering molecules. However, the apoptosis-triggering signals are formed farther from the precancerous cells, so that these are attacked less efficiently. Spatial effects thus may represent a novel analogue of negative feedback mechanisms.
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Affiliation(s)
- Pavel Kundrát
- Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München-German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - Werner Friedland
- Institute of Radiation Protection, Department of Radiation Sciences, Helmholtz Zentrum München-German Research Center for Environmental Health (GmbH), Neuherberg, Germany
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11
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Maraprygsavan P, Mongkolsuk J, Arnhold J, Kuehne FW. The chlorite-based drug WF10 constantly reduces hemoglobin A1c values and improves glucose control in diabetes patients with severe foot syndrome. JOURNAL OF CLINICAL AND TRANSLATIONAL ENDOCRINOLOGY 2016; 4:53-58. [PMID: 29159131 PMCID: PMC5680448 DOI: 10.1016/j.jcte.2016.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 05/02/2016] [Indexed: 12/22/2022]
Abstract
The chlorite-based drug WF10 improved healing of foot wounds in diabetic patients. Infusion with WF10 markedly reduced HbA1c values in patients with diabetic foot syndrome. After administration of WF10 HbA1c values remained low over at least 8 to 12 weeks. The chlorite component of WF10 is known to inactivate efficiently cytotoxic hemoglobin forms. This treatment prevented below knee amputation in patients with diabetic foot syndrome.
Aims The intravenous application of the chlorite-based drug solution WF10 is known to improve wound healing in patients with diabetic foot syndrome. In this retrospective study, we addressed the question, which effects are caused by this drug in patients with diabetic foot ulcers on the hemoglobin A1c value. Methods Patients received five consecutive daily infusions of WF10. Three patients received a second cycle of WF10, and one patient a third cycle. Results On a group of twelve patients with diabetic foot syndrome, WF10 gradually reduced the HbA1c values from a high-risk range (9.1 ± 1.6% (76 ± 13 mmol/mol)) into a low-risk range in all patients but one. These values remain low over at least 8 to 12 weeks after the administration of WF10. This drug improved also considerably wound healing processes in eleven patients. Conclusions The chlorite component of WF10 is known to inactivate efficiently free cytotoxic hemoglobin forms that might accumulate in peripheral blood after hemolysis and induces the removal of pre-damaged red blood cells from circulation. By these mechanisms WF10 diminished toxic effects of hemolysis, improved microcirculation and glucose consumption in affected tissues, and prevented, thus, below knee amputation.
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Affiliation(s)
| | | | - Juergen Arnhold
- Institute of Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Leipzig, Germany
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12
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Pichert A, Arnhold J. Interaction of the chlorite-based drug WF10 and chlorite with hemoglobin, methemoglobin and ferryl hemoglobin. Arch Biochem Biophys 2015; 585:82-89. [DOI: 10.1016/j.abb.2015.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 09/10/2015] [Accepted: 09/11/2015] [Indexed: 01/06/2023]
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13
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Schaffner I, Hofbauer S, Krutzler M, Pirker KF, Furtmüller PG, Obinger C. Mechanism of chlorite degradation to chloride and dioxygen by the enzyme chlorite dismutase. Arch Biochem Biophys 2015; 574:18-26. [PMID: 25748001 DOI: 10.1016/j.abb.2015.02.031] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Revised: 02/19/2015] [Accepted: 02/25/2015] [Indexed: 11/18/2022]
Abstract
Heme b containing chlorite dismutase (Cld) catalyses the conversion of chlorite to chloride and dioxygen which includes an unusual OO bond formation. This review summarizes our knowledge about the interaction of chlorite with heme enzymes and introduces the biological role, phylogeny and structure of functional chlorite dismutases with differences in overall structure and subunit architecture. The paper sums up the available experimental and computational studies on chlorite degradation by water soluble porphyrin complexes as well as a model based on the active site of Cld. Finally, it reports the available biochemical and biophysical data of Clds from different organisms which allow the presentation of a general reaction mechanism. It includes binding of chlorite to ferric Cld followed by subsequent heterolytic OCl bond cleavage leading to the formation of Compound I and hypochlorite, which finally recombine for production of chloride and O2. The role of the Cld-typical distal arginine in catalysis is discussed together with the pH dependence of the reaction and the role of transiently produced hypochlorite in irreversible inactivation of the enzyme.
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Affiliation(s)
- Irene Schaffner
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Stefan Hofbauer
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria; Department for Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, A-1030 Vienna, Austria
| | - Michael Krutzler
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Katharina F Pirker
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Paul G Furtmüller
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Christian Obinger
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria.
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14
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Abstract
O₂-generating reactions are exceedingly rare in biology and difficult to mimic synthetically. Perchlorate-respiring bacteria enzymatically detoxify chlorite (ClO₂(-) ), the end product of the perchlorate (ClO(4)(-) ) respiratory pathway, by rapidly converting it to dioxygen (O₂) and chloride (Cl(-)). This reaction is catalyzed by a heme-containing protein, called chlorite dismutase (Cld), which bears no structural or sequence relationships with known peroxidases or other heme proteins and is part of a large family of proteins with more than one biochemical function. The original assumptions from the 1990s that perchlorate is not a natural product and that perchlorate respiration might be confined to a taxonomically narrow group of species have been called into question, as have the roles of perchlorate respiration and Cld-mediated reactions in the global biogeochemical cycle of chlorine. In this chapter, the chemistry and biochemistry of Cld-mediated O₂generation, as well as the biological and geochemical context of this extraordinary reaction, are described.
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Affiliation(s)
- Jennifer L DuBois
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717, USA,
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15
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Celis AI, Geeraerts Z, Ngmenterebo D, Machovina MM, Kurker RC, Rajakumar K, Ivancich A, Rodgers KR, Lukat-Rodgers GS, DuBois JL. A dimeric chlorite dismutase exhibits O2-generating activity and acts as a chlorite antioxidant in Klebsiella pneumoniae MGH 78578. Biochemistry 2014; 54:434-46. [PMID: 25437493 PMCID: PMC4303309 DOI: 10.1021/bi501184c] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
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Chlorite
dismutases (Clds) convert chlorite to O2 and
Cl–, stabilizing heme in the presence of strong
oxidants and forming the O=O bond with high efficiency. The
enzyme from the pathogen Klebsiella pneumoniae (KpCld) represents a subfamily of Clds that share most of
their active site structure with efficient O2-producing
Clds, even though they have a truncated monomeric structure, exist
as a dimer rather than a pentamer, and come from Gram-negative bacteria
without a known need to degrade chlorite. We hypothesized that KpCld, like others in its subfamily, should be able to make
O2 and may serve an in vivo antioxidant
function. Here, it is demonstrated that it degrades chlorite with
limited turnovers relative to the respiratory Clds, in part because
of the loss of hypochlorous acid from the active site and destruction
of the heme. The observation of hypochlorous acid, the expected leaving
group accompanying transfer of an oxygen atom to the ferric heme,
is consistent with the more open, solvent-exposed heme environment
predicted by spectroscopic measurements and inferred from the crystal
structures of related proteins. KpCld is more susceptible
to oxidative degradation under turnover conditions than the well-characterized
Clds associated with perchlorate respiration. However, wild-type K. pneumoniae has a significant growth advantage in the
presence of chlorate relative to a Δcld knockout
strain, specifically under nitrate-respiring conditions. This suggests
that a physiological function of KpCld may be detoxification
of endogenously produced chlorite.
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Affiliation(s)
- Arianna I Celis
- Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59715, United States
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16
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Hofbauer S, Gruber C, Pirker KF, Sündermann A, Schaffner I, Jakopitsch C, Oostenbrink C, Furtmüller PG, Obinger C. Transiently produced hypochlorite is responsible for the irreversible inhibition of chlorite dismutase. Biochemistry 2014; 53:3145-57. [PMID: 24754261 PMCID: PMC4029776 DOI: 10.1021/bi500401k] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Chlorite dismutases (Clds) are heme b-containing prokaryotic oxidoreductases that catalyze the reduction of chlorite to chloride with the concomitant release of molecular oxygen. Over time, they are irreversibly inactivated. To elucidate the mechanism of inactivation and investigate the role of the postulated intermediate hypochlorite, the pentameric chlorite dismutase of "Candidatus Nitrospira defluvii" (NdCld) and two variants (having the conserved distal arginine 173 exchanged with alanine and lysine) were recombinantly produced in Escherichia coli. Exchange of the distal arginine boosts the extent of irreversible inactivation. In the presence of the hypochlorite traps methionine, monochlorodimedone, and 2-[6-(4-aminophenoxy)-3-oxo-3H-xanthen-9-yl]benzoic acid, the extent of chlorite degradation and release of molecular oxygen is significantly increased, whereas heme bleaching and oxidative modifications of the protein are suppressed. Among other modifications, hypochlorite-mediated formation of chlorinated tyrosines is demonstrated by mass spectrometry. The data obtained were analyzed with respect to the proposed reaction mechanism for chlorite degradation and its dependence on pH. We discuss the role of distal Arg173 by keeping hypochlorite in the reaction sphere for O-O bond formation.
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Affiliation(s)
- Stefan Hofbauer
- Department of Chemistry, Division of Biochemistry, VIBT-Vienna Institute of BioTechnology, BOKU-University of Natural Resources and Life Sciences , A-1190 Vienna, Austria
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17
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Jakopitsch C, Pirker KF, Flemmig J, Hofbauer S, Schlorke D, Furtmüller PG, Arnhold J, Obinger C. Mechanism of reaction of chlorite with mammalian heme peroxidases. J Inorg Biochem 2014; 135:10-9. [PMID: 24632343 PMCID: PMC4003552 DOI: 10.1016/j.jinorgbio.2014.02.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/19/2014] [Accepted: 02/19/2014] [Indexed: 01/09/2023]
Abstract
This study demonstrates that heme peroxidases from different superfamilies react differently with chlorite. In contrast to plant peroxidases, like horseradish peroxidase (HRP), the mammalian counterparts myeloperoxidase (MPO) and lactoperoxidase (LPO) are rapidly and irreversibly inactivated by chlorite in the micromolar concentration range. Chlorite acts as efficient one-electron donor for Compound I and Compound II of MPO and LPO and reacts with the corresponding ferric resting states in a biphasic manner. The first (rapid) phase is shown to correspond to the formation of a MPO-chlorite high-spin complex, whereas during the second (slower) phase degradation of the prosthetic group was observed. Cyanide, chloride and hydrogen peroxide can block or delay heme bleaching. In contrast to HRP, the MPO/chlorite system does not mediate chlorination of target molecules. Irreversible inactivation is shown to include heme degradation, iron release and decrease in thermal stability. Differences between mammalian peroxidases and HRP are discussed with respect to differences in active site architecture and heme modification.
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Affiliation(s)
- Christa Jakopitsch
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Katharina F Pirker
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Jörg Flemmig
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Härtelstr 16-18, D-04107 Leipzig, Germany; Translational Centre for Regenerative Medicine, University of Leipzig, Philipp-Rosenthal-Strasse 55, D-04103 Leipzig, Germany
| | - Stefan Hofbauer
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Denise Schlorke
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Härtelstr 16-18, D-04107 Leipzig, Germany
| | - Paul G Furtmüller
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Jürgen Arnhold
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Härtelstr 16-18, D-04107 Leipzig, Germany; Translational Centre for Regenerative Medicine, University of Leipzig, Philipp-Rosenthal-Strasse 55, D-04103 Leipzig, Germany
| | - Christian Obinger
- Department of Chemistry, Division of Biochemistry, BOKU - University of Natural Resources and Life Sciences, Muthgasse 18, A-1190 Vienna, Austria.
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18
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Mayfield JA, Blanc B, Rodgers KR, Lukat-Rodgers GS, DuBois JL. Peroxidase-type reactions suggest a heterolytic/nucleophilic O-O joining mechanism in the heme-dependent chlorite dismutase. Biochemistry 2013; 52:6982-94. [PMID: 24001266 DOI: 10.1021/bi4005599] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Heme-containing chlorite dismutases (Clds) catalyze a highly unusual O-O bond-forming reaction. The O-O cleaving reactions of hydrogen peroxide and peracetic acid (PAA) with the Cld from Dechloromonas aromatica (DaCld) were studied to better understand the Cl-O cleavage of the natural substrate and subsequent O-O bond formation. While reactions with H2O2 result in slow destruction of the heme, at acidic pH heterolytic cleavage of the O-O bond of PAA cleanly yields the ferryl porphyrin cation radical (compound I). At alkaline pH, the reaction proceeds more rapidly, and the first observed intermediate is a ferryl heme. Freeze-quench EPR confirmed that the latter has an uncoupled protein-based radical, indicating that compound I is the first intermediate formed at all pH values and that radical migration is faster at alkaline pH. These results suggest by analogy that two-electron Cl-O bond cleavage to yield a ferryl-porphyrin cation radical is the most likely initial step in O-O bond formation from chlorite.
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Affiliation(s)
- Jeffrey A Mayfield
- Department of Chemistry and Biochemistry, University of Notre Dame , Notre Dame, Indiana 46556, United States
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19
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Umile TP, Wang D, Groves JT. Dissection of the Mechanism of Manganese Porphyrin-Catalyzed Chlorine Dioxide Generation. Inorg Chem 2011; 50:10353-62. [DOI: 10.1021/ic201430v] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Thomas P. Umile
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Dong Wang
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - John T. Groves
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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20
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Umile TP, Groves JT. Catalytic generation of chlorine dioxide from chlorite using a water-soluble manganese porphyrin. Angew Chem Int Ed Engl 2010; 50:695-8. [PMID: 21226156 DOI: 10.1002/anie.201004482] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2010] [Revised: 10/22/2010] [Indexed: 11/08/2022]
Affiliation(s)
- Thomas P Umile
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
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21
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Umile TP, Groves JT. Catalytic Generation of Chlorine Dioxide from Chlorite Using a Water-Soluble Manganese Porphyrin. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.201004482] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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22
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Goblirsch BR, Streit BR, DuBois JL, Wilmot CM. Structural features promoting dioxygen production by Dechloromonas aromatica chlorite dismutase. J Biol Inorg Chem 2010; 15:879-88. [PMID: 20386942 PMCID: PMC2909366 DOI: 10.1007/s00775-010-0651-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Accepted: 03/14/2010] [Indexed: 10/19/2022]
Abstract
Chlorite dismutase (Cld) is a heme enzyme capable of rapidly and selectively decomposing chlorite (ClO(2) (-)) to Cl(-) and O(2). The ability of Cld to promote O(2) formation from ClO(2) (-) is unusual. Heme enzymes generally utilize ClO(2) (-) as an oxidant for reactions such as oxygen atom transfer to, or halogenation of, a second substrate. The X-ray crystal structure of Dechloromonas aromatica Cld co-crystallized with the substrate analogue nitrite (NO(2) (-)) was determined to investigate features responsible for this novel reactivity. The enzyme active site contains a single b-type heme coordinated by a proximal histidine residue. Structural analysis identified a glutamate residue hydrogen-bonded to the heme proximal histidine that may stabilize reactive heme species. A solvent-exposed arginine residue likely gates substrate entry to a tightly confined distal pocket. On the basis of the proposed mechanism of Cld, initial reaction of ClO(2) (-) within the distal pocket generates hypochlorite (ClO(-)) and a compound I intermediate. The sterically restrictive distal pocket probably facilitates the rapid rebound of ClO(-) with compound I forming the Cl(-) and O(2) products. Common to other heme enzymes, Cld is inactivated after a finite number of turnovers, potentially via the observed formation of an off-pathway tryptophanyl radical species through electron migration to compound I. Three tryptophan residues of Cld have been identified as candidates for this off-pathway radical. Finally, a juxtaposition of hydrophobic residues between the distal pocket and the enzyme surface suggests O(2) may have a preferential direction for exiting the active site.
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Affiliation(s)
- Brandon R. Goblirsch
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
| | - Bennett R. Streit
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Jennifer L. DuBois
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Carrie M. Wilmot
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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23
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Mechanism of and exquisite selectivity for O-O bond formation by the heme-dependent chlorite dismutase. Proc Natl Acad Sci U S A 2008; 105:15654-9. [PMID: 18840691 DOI: 10.1073/pnas.0804279105] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Chlorite dismutase (Cld) is a heme b-dependent, O-O bond forming enzyme that transforms toxic chlorite (ClO(2)(-)) into innocuous chloride and molecular oxygen. The mechanism and specificity of the reaction with chlorite and alternate oxidants were investigated. Chlorite is the sole source of dioxygen as determined by oxygen-18 labeling studies. Based on ion chromatography and mass spectrometry results, Cld is highly specific for the dismutation of chlorite to chloride and dioxygen with no other side products. Cld does not use chlorite as an oxidant for oxygen atom transfer and halogenation reactions (using cosubstrates guaiacol, thioanisole, and monochlorodimedone, respectively). When peracetic acid or H(2)O(2) was used as an alternative oxidant, oxidation and oxygen atom transfer but not halogenation reactions occurred. Monitoring the reaction of Cld with peracetic acid by rapid-mixing UV-visible spectroscopy, the formation of the high valent compound I intermediate, [(Por(*+))Fe(IV) = O], was observed [k(1) = (1.28 +/- 0.04) x 10(6) M(-1) s(-1)]. Compound I readily decayed to form compound II in a manner that is independent of peracetic acid concentration (k(2) = 170 +/- 20 s(-1)). Both compound I and a compound II-associated tryptophanyl radical that resembles cytochrome c peroxidase (Ccp) compound I were observed by EPR under freeze-quench conditions. The data collectively suggest an O-O bond-forming mechanism involving generation of a compound I intermediate via oxygen atom transfer from chlorite, and subsequent recombination of the resulting hypochlorite and compound I.
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24
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Streit BR, DuBois JL. Chemical and steady-state kinetic analyses of a heterologously expressed heme dependent chlorite dismutase. Biochemistry 2008; 47:5271-80. [PMID: 18422344 DOI: 10.1021/bi800163x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chlorite dismutase carries out the heme-catalyzed decomposition of ClO2- to Cl- and O2, an unusual transformation with biotechnological and bioremediative applications. The enzyme has been successfully overexpressed for the first time in highly functional form in Escherichia coli and its steady state kinetics studied. The purified enzyme is abundant (55 mg/L cell culture), highly active (approximately 4.7 x 10(3) micromol of ClO2- min(-1) mg(-1) subunit) and nearly stoichiometric in heme; further, it shares spectroscopic and physicochemical features with chlorite dismutases previously isolated from three organisms. A careful study of the enzyme's steady state kinetics has been carried out. ClO2- consumption and O2 release rates were measured, yielding comparable values of kcat (4.5 x 10(5) min(-1)), K(m) (approximately 215 microM), and kcat/Km (3.5 x 10(7) M(-1) s(-1) via either method (4 degrees C, pH 6.8; all values referenced per heme-containing subunit). ClO2-:O2 stoichiometry exhibited a 1:1 relationship under all conditions measured. Though the value of kcat/Km indicates near diffusion control of the reaction, viscosogens had no effect on k(cat)/K(m) or V(max). The product O2 did not inhibit the reaction at saturating [O2], but Cl- is a mixed inhibitor with relatively high values of KI (225 mM for enzyme and 95.6 mM for the enzyme-substrate complex), indicating a relatively low affinity of the heme iron for halogen ions. Chlorite irreversibly inactivates the enzyme after approximately 1.7 x 10(4) turnovers (per heme) and with a half-life of 0.39 min, resulting in bleaching of the heme chromophore. The inactivation K(I) (K(inact)) of 166 microM is similar in magnitude to Km, consistent with a common Michaelis complex on the pathway to both reaction and inactivation. The one-electron peroxidase substrate guaiacol offers incomplete protection of the enzyme from inactivation. Mechanisms in keeping with the available data and the properties of other well-described heme enzymes are proposed.
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Affiliation(s)
- Bennett R Streit
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556, USA
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