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Bhunia S, Ghatak A, Dey A. Second Sphere Effects on Oxygen Reduction and Peroxide Activation by Mononuclear Iron Porphyrins and Related Systems. Chem Rev 2022; 122:12370-12426. [PMID: 35404575 DOI: 10.1021/acs.chemrev.1c01021] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Activation and reduction of O2 and H2O2 by synthetic and biosynthetic iron porphyrin models have proved to be a versatile platform for evaluating second-sphere effects deemed important in naturally occurring heme active sites. Advances in synthetic techniques have made it possible to install different functional groups around the porphyrin ligand, recreating artificial analogues of the proximal and distal sites encountered in the heme proteins. Using judicious choices of these substituents, several of the elegant second-sphere effects that are proposed to be important in the reactivity of key heme proteins have been evaluated under controlled environments, adding fundamental insight into the roles played by these weak interactions in nature. This review presents a detailed description of these efforts and how these have not only demystified these second-sphere effects but also how the knowledge obtained resulted in functional mimics of these heme enzymes.
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Affiliation(s)
- Sarmistha Bhunia
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
| | - Arnab Ghatak
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
| | - Abhishek Dey
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
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2
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Sanyal R, Bhagi-Damodaran A. An enzymatic method for precise oxygen affinity measurements over nanomolar-to-millimolar concentration regime. J Biol Inorg Chem 2020; 25:181-186. [PMID: 31897725 DOI: 10.1007/s00775-019-01750-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 12/03/2019] [Indexed: 10/25/2022]
Abstract
Oxygen affinity is an important property of metalloproteins that helps elucidate their reactivity profile and mechanism. Heretofore, oxygen affinity values were determined either using flash photolysis and polarography techniques that require expensive instrumentation, or using oxygen titration methods which are erroneous at low nanomolar and at high millimolar oxygen concentrations. Here, we describe an inexpensive, easy-to-setup, and a one-pot method for oxygen affinity measurements that uses the enzyme chlorite dismutase (Cld) as a precise in situ oxygen source. Using this method, we measure thermodynamic and kinetic oxygen affinities (Kd and KM) of different classes of heme and non-heme metalloproteins involved in oxygen transport, sensing, and catalysis. The method enables oxygen affinity measurements over a wide concentration range from 10 nM to 5 mM which is unattainable by simply diluting oxygen-saturated buffers. In turn, we were able to precisely measure oxygen affinities of a model set of eight different metalloproteins with affinities ranging from 48 ± 3 nM to 1.18 ± 0.03 mM. Overall, the Cld method is easy and inexpensive to set up, requires significantly lower quantities of protein, enables precise oxygen affinity measurements, and is applicable for proteins exhibiting nanomolar-to-millimolar affinity values.
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Affiliation(s)
- Ria Sanyal
- Department of Chemistry, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA
| | - Ambika Bhagi-Damodaran
- Department of Chemistry, University of Minnesota, Twin Cities, Minneapolis, MN, 55455, USA.
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3
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Shrestha R, Chen X, Ramyar KX, Hayati Z, Carlson EA, Bossmann SH, Song L, Geisbrecht BV, Li P. Identification of Surface-Exposed Protein Radicals and A Substrate Oxidation Site in A-Class Dye-Decolorizing Peroxidase from Thermomonospora curvata. ACS Catal 2016; 6:8036-8047. [PMID: 29308294 DOI: 10.1021/acscatal.6b01952] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dye-decolorizing peroxidases (DyPs) are a family of heme peroxidases, in which a catalytic distal aspartate is involved in H2O2 activation to catalyze oxidations in acidic conditions. They have received much attention due to their potential applications in lignin compound degradation and biofuel production from biomass. However, the mode of oxidation in bacterial DyPs remains unknown. We have recently reported that the bacterial TcDyP from Thermomonospora curvata is among the most active DyPs and shows activity toward phenolic lignin model compounds (J. Biol. Chem.2015, 290, 23447). Based on the X-ray crystal structure solved at 1.75 Å, sigmoidal steady-state kinetics with Reactive Blue 19 (RB19), and formation of compound II-like product in the absence of reducing substrates observed with stopped-flow spectroscopy and electron paramagnetic resonance (EPR), we hypothesized that the TcDyP catalyzes oxidation of large-size substrates via multiple surface-exposed protein radicals. Among 7 tryptophans and 3 tyrosines in TcDyP consisting of 376 residues for the matured protein, W263, W376, and Y332 were identified as surface-exposed protein radicals. Only the W263 was also characterized as one of surface-exposed oxidation sites. SDS-PAGE and size-exclusion chromatography demonstrated that W376 represents an off-pathway destination for electron transfer, resulting in the crosslinking of proteins in the absence of substrates. Mutation of W376 improved compound I stability and overall catalytic efficiency toward RB19. While Y332 is highly conserved across all four classes of DyPs, its catalytic function in A-class TcDyP is minimal possibly due to its extremely small solvent accessible areas. Identification of surface-exposed protein radicals and substrate oxidation sites is important for understanding DyP mechanism and modulating its catalytic functions for improved activity on phenolic lignin.
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Affiliation(s)
| | | | | | - Zahra Hayati
- National
High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
| | | | | | - Likai Song
- National
High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, United States
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4
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Alberti MN, Polyhach Y, Tzirakis MD, Tödtli L, Jeschke G, Diederich F. Exploring the Strength of the H-Bond in Synthetic Models for Heme Proteins: The Importance of the N−H Acidity of the Distal Base. Chemistry 2016; 22:10194-202. [DOI: 10.1002/chem.201601505] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Indexed: 11/10/2022]
Affiliation(s)
- Mariza N. Alberti
- Laboratorium für Organische Chemie; ETH Zurich; Vladimir-Prelog-Weg 3 8093 Zurich Switzerland
| | - Yevhen Polyhach
- Laboratory of Physical Chemistry; ETH Zurich; Vladimir-Prelog-Weg 2 8093 Zurich Switzerland
| | - Manolis D. Tzirakis
- Laboratorium für Organische Chemie; ETH Zurich; Vladimir-Prelog-Weg 3 8093 Zurich Switzerland
| | - Laura Tödtli
- Laboratory of Physical Chemistry; ETH Zurich; Vladimir-Prelog-Weg 2 8093 Zurich Switzerland
| | - Gunnar Jeschke
- Laboratory of Physical Chemistry; ETH Zurich; Vladimir-Prelog-Weg 2 8093 Zurich Switzerland
| | - François Diederich
- Laboratorium für Organische Chemie; ETH Zurich; Vladimir-Prelog-Weg 3 8093 Zurich Switzerland
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5
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Poloznikov AA, Zakharova GS, Chubar TA, Hushpulian DM, Tishkov VI, Gazaryan IG. Site-directed mutagenesis of tobacco anionic peroxidase: Effect of additional aromatic amino acids on stability and activity. Biochimie 2015; 115:71-7. [PMID: 25957835 DOI: 10.1016/j.biochi.2015.04.021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 04/27/2015] [Indexed: 11/19/2022]
Abstract
Tobacco anionic peroxidase (TOP) is known to effectively catalyze luminol oxidation without enhancers, in contrast to horseradish peroxidase (HRP). To pursue structure-activity relationship studies for TOP, two amino acids have been chosen for mutation, namely Thr151, close to the heme plane, and Phe140 at the entrance to the active site pocket. Three mutant forms TOP F140Y, T151W and F140Y/T151W have been expressed in Escherichia coli, and reactivated to yield active enzymes. Single-point mutations introducing additional aromatic amino acid residues at the surface of TOP exhibit a significant effect on the enzyme catalytic activity and stability as judged by the results of steady-state and transient kinetics studies. TOP T151W is up to 4-fold more active towards a number of aromatic substrates including luminol, whereas TOP F140Y is 2-fold more stable against thermal inactivation and 8-fold more stable in the reaction course. These steady-state observations have been rationalized with the help of transient kinetic studies on the enzyme reaction with hydrogen peroxide in a single turnover regime. The stopped-flow data reveal (a) an increased stability of F140Y Compound I towards hydrogen peroxide, and thus, a higher operational stability as compared to the wild-type enzyme, and (b) a lesser leakage of oxidative equivalents from TOP T151W Compound I resulting in the increased catalytic activity. The results obtained show that TOP unique properties can be further improved for practical applications by site-directed mutagenesis.
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Affiliation(s)
- A A Poloznikov
- Chemistry Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia; Innovations and High Technologies MSU Ltd, 109559 Moscow, Russia.
| | - G S Zakharova
- Innovations and High Technologies MSU Ltd, 109559 Moscow, Russia; A.N. Bach Institute of Biochemistry, RAS, 119071 Moscow, Russia
| | - T A Chubar
- Chemistry Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia
| | - D M Hushpulian
- Chemistry Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia; Innovations and High Technologies MSU Ltd, 109559 Moscow, Russia
| | - V I Tishkov
- Chemistry Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia; Innovations and High Technologies MSU Ltd, 109559 Moscow, Russia; A.N. Bach Institute of Biochemistry, RAS, 119071 Moscow, Russia
| | - I G Gazaryan
- Chemistry Faculty, Lomonosov Moscow State University, 119992 Moscow, Russia; Burke Medical Research Institute, Department of Neurology and Neuroscience, Weill Medical College of Cornell University, 785 Mamaroneck Ave, White Plains, NY 10605, USA
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6
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Complexes of ferriheme nitrophorin 4 with low-molecular weight thiol(ate)s occurring in blood plasma. J Inorg Biochem 2013; 122:38-48. [DOI: 10.1016/j.jinorgbio.2013.01.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 01/14/2013] [Accepted: 01/14/2013] [Indexed: 11/17/2022]
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Millett ES, Efimov I, Basran J, Handa S, Mowat CG, Raven EL. Heme-containing dioxygenases involved in tryptophan oxidation. Curr Opin Chem Biol 2012; 16:60-6. [DOI: 10.1016/j.cbpa.2012.01.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2011] [Revised: 01/18/2012] [Accepted: 01/25/2012] [Indexed: 10/28/2022]
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8
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Yi J, Thomas LM, Richter-Addo GB. Distal Pocket Control of Nitrite Binding in Myoglobin. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201200010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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9
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Yi J, Thomas LM, Richter-Addo GB. Distal Pocket Control of Nitrite Binding in Myoglobin. Angew Chem Int Ed Engl 2012; 51:3625-7. [DOI: 10.1002/anie.201200010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2012] [Indexed: 11/09/2022]
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10
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Nitrite reduction by CoII and MnII substituted myoglobins. J Inorg Biochem 2012; 107:47-53. [DOI: 10.1016/j.jinorgbio.2011.10.006] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 09/28/2011] [Accepted: 10/17/2011] [Indexed: 11/22/2022]
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Hayashi T, Sato H, Matsuo T, Matsuda T, Hitomi Y, Hisaeda Y. Enhancement of enzymatic activity for myoglobins by modification of heme-propionate side chains. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424604000246] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The modification of myoglobin is an attractive process not only for understanding its molecular mechanism but also for engineering the protein function. The strategy of myoglobin functionalization can be divided into at least two approaches: site-directed mutagenesis and reconstitution with a non-natural prosthetic group. The former method enables us to mainly modulate the physiological function, while the latter has the advantage of introducing a new function on the protein. Particularly, replacement of the native hemin with an artificially created hemin having hydrophobic moieties at the terminal of the heme-propionate side chains serves as an appropriate substrate-binding site near the heme pocket, and consequently enhances the peroxidase and peroxygenase activities for the reconstituted myoglobin. In addition, the incorporation of the synthetic hemin bearing modified heme-propionates into an appropriate apomyoglobin mutant drastically enhances the peroxidase activity. In contrast, to convert myoglobin into a cytochrome P450 enzyme, a flavin moiety as an electron transfer mediator was introduced at the terminal of the heme-propionate side chain. The flavomyoglobin catalyzes the deformylation of 2-phenylpropanal in the presence of NADH under aerobic conditions through the peroxoanion formation from the oxygenated species. In addition, modification of the heme-propionate side chains has an significant influence on regulating the reactivity of the horseradish peroxidase. Furthermore, the heme-propionate side chain can form a metal binding site with a carboxylate residue in the heme pocket. These studies indicate that modification of the heme-propionate side chains can be a new and effective way to engineer functions for the hemoproteins.
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Affiliation(s)
- Takashi Hayashi
- PRESTO Japan Science and Technology Agency (JST), Japan
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581, Japan
| | - Hideaki Sato
- PRESTO Japan Science and Technology Agency (JST), Japan
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581, Japan
| | - Takashi Matsuo
- PRESTO Japan Science and Technology Agency (JST), Japan
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581, Japan
| | - Takaaki Matsuda
- PRESTO Japan Science and Technology Agency (JST), Japan
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581, Japan
| | - Yutaka Hitomi
- Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan
| | - Yoshio Hisaeda
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581, Japan
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Matsuo T, Hayashi T. Electron transfer and oxidase activities in reconstituted hemoproteins with chemically modified cofactors. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424609001340] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Protoheme IX is a typical iron porphyrin cofactor, showing a variety of reactivities in many hemoproteins under the reaction environments provided by protein matrices. Chemical modification of the protoheme cofactor is expected to be a versatile strategy to design hemoproteins possessing unique functions. This review focuses on the conversion of a hemoprotein, mainly myoglobin (an oxygen-storage hemoprotein), into a protein having different functions from the original ones by replacement of the protoheme cofactor with synthetic cofactors. The myoglobin having anionic patches pended to the heme propionates effectively binds electron-accepting proteins or small cationic organic molecules on the protein surface, resulting in enhanced efficiency of the photoinduced electron transfers from the myoglobin to these electron acceptors. Furthermore, the peroxidase and peroxygenase activities are also enhanced due to the facile substrate accesses. The attachment of the chemically active moiety such as flavin at the heme terminal is also important to give P450-like function to the native myoglobin. The employment of a structural isomer of porphyrin as an artificial cofactor gives rise to remarkably high dioxygen affinity and peroxidase activity in myoglobin, and allows us to easily detect high-valent species of the porphyrin isomer in HRP. These examples provide a clear insight into hemoprotein modifications based on synthetic chemistry as well as genetic amino acid mutations.
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Affiliation(s)
- Takashi Matsuo
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
| | - Takashi Hayashi
- Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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Matsuo T, Fukumoto K, Watanabe T, Hayashi T. Precise Design of Artificial Cofactors for Enhancing Peroxidase Activity of Myoglobin: Myoglobin Mutant H64D Reconstituted with a “Single-Winged Cofactor” Is Equivalent to Native Horseradish Peroxidase in Oxidation Activity. Chem Asian J 2011; 6:2491-9. [DOI: 10.1002/asia.201100107] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2011] [Indexed: 11/09/2022]
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14
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Dube H, Kasumaj B, Calle C, Felber B, Saito M, Jeschke G, Diederich F. Probing Hydrogen Bonding to Bound Dioxygen in Synthetic Models for Heme Proteins: The Importance of Precise Geometry. Chemistry 2009; 15:125-35. [DOI: 10.1002/chem.200802077] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Lu H, Rusling JF, Hu N. Protecting peroxidase activity of multilayer enzyme-polyion films using outer catalase layers. J Phys Chem B 2007; 111:14378-86. [PMID: 18052272 PMCID: PMC2546493 DOI: 10.1021/jp076036w] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Films constructed layer-by-layer on electrodes with architecture {protein/hyaluronic acid (HA)}n containing myoglobin (Mb) or horseradish peroxidase (HRP) were protected against protein damage by H2O2 by using outer catalase layers. Peroxidase activity for substrate oxidation requires activation by H2O2, but {protein/HA}n films without outer catalase layers are damaged slowly and irreversibly by H2O2. The rate and extent of damage were decreased dramatically by adding outer catalase layers to decompose H2O2. Comparative studies suggest that protection results from catalase decomposing a fraction of the H2O2 as it enters the film, rather than by an in-film diffusion barrier. The outer catalase layers controlled the rate of H2O2 entry into inner regions of the film, and they biased the system to favor electrocatalytic peroxide reduction over enzyme damage. Catalase-protected {protein/HA}n films had an increased linear concentration range for H2O2 detection. This approach offers an effective way to protect biosensors from damage by H2O2.
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Affiliation(s)
- Haiyun Lu
- Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
| | - James F. Rusling
- Department of Chemistry, University of Connecticut, U-60, Storrs, CT 06269-3060, USA
- Department of Pharmacology, University of Connecticut Health Center, Farmington, CT 06032, USA
| | - Naifei Hu
- Department of Chemistry, Beijing Normal University, Beijing 100875, P. R. China
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Sato H, Hayashi T, Ando T, Hisaeda Y, Ueno T, Watanabe Y. Hybridization of Modified-Heme Reconstitution and Distal Histidine Mutation to Functionalize Sperm Whale Myoglobin. J Am Chem Soc 2003; 126:436-7. [PMID: 14719919 DOI: 10.1021/ja038798k] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To modulate the physiological function of a hemoprotein, most approaches have been demonstrated by site-directed mutagenesis. Replacement of the native heme with an artificial prosthetic group is another way to modify a hemoprotein. However, an alternate method, mutation or heme reconstitution, does not always demonstrate sufficient improvement compared with the native heme enzyme. In the present study, to convert a simple oxygen storage hemoprotein, myoglobin, into an active peroxidase, we applied both methods at the same time. The native heme of myoglobin was replaced with a chemically modified heme 2 having two aromatic rings at the heme-propionate termini. The constructed myoglobins were examined for 2-methoxyphenol (guaiacol) oxidation in the presence of H2O2. Compared with native myoglobin, rMb(H64D.2) showed a 430-fold higher kcat/Km value, which is significantly higher than that of cytochrome c peroxidase and only 3-fold less than that of horseradish peroxidase. In addition, myoglobin-catalyzed degradation of bisphenol A was examined by HPLC analysis. The rMb(H64D.2) showed drastic acceleration (>35-fold) of bisphenol A degradation compared with the native myoglobin. In this system, a highly oxidized heme reactive species is smoothly generated and a substrate is effectively bound in the heme pocket, while native myoglobin only reversibly binds dioxygen. The present results indicate that the combination of a modified-heme reconstitution and an amino acid mutation should offer interesting perspectives toward developing a useful biomolecule catalyst from a hemoprotein.
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Affiliation(s)
- Hideaki Sato
- PRESTO, Japan Science and Technology Agency, Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, Fukuoka 812-8581, Japan
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Hayashi T, Dejima H, Matsuo T, Sato H, Murata D, Hisaeda Y. Blue myoglobin reconstituted with an iron porphycene shows extremely high oxygen affinity. J Am Chem Soc 2002; 124:11226-7. [PMID: 12236710 DOI: 10.1021/ja0265052] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Myoglobin will be a good scaffold for engineering a function into proteins. To modulate the physiological function of myoglobin, almost all approaches have been demonstrated by site-directed mutagenesis, however, there are few studies which show a significant improvement in the function. In contrast, we focused on the replacement of heme in the protein with an artificial prosthetic group. Recently, we prepared a novel myoglobin reconstituted with an iron porphycene as a structural isomer of mesoheme. The bluish colored reconstituted myoglobin is relatively stable and the deoxymyoglobin reversibly binds ligands. Interestingly, the O2 affinity of the reconstituted myoglobin, 1.1 x 109 M-1, is a significant 1,400-fold higher than that of the native myoglobin. Furthermore, the unfavorable autoxidation kinetics show 7-fold decrease in rate for the reconstituted myoglobin relative to the native myoglobin, indicating the stable oxy-form against autoxidation. The net results come from the slow dissociation of the O2 ligand in the reconstituted myoglobin, koff = 0.11 s-1, because of the formation of strong hydrogen bond between His64 and negatively charged dioxygen. The present study indicates that the replacement of native heme with an artificially created prosthetic group will give us a unique function into a hemoprotein.
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Affiliation(s)
- Takashi Hayashi
- Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, and PRESTO in Japan Science and Technology Corporation, Fukuoka 812-8581, Japan.
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Witting PK, Mauk AG. Reaction of human myoglobin and H2O2. Electron transfer between tyrosine 103 phenoxyl radical and cysteine 110 yields a protein-thiyl radical. J Biol Chem 2001; 276:16540-7. [PMID: 11278969 DOI: 10.1074/jbc.m011707200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The sequence of human myoglobin (Mb) is similar to that of other species except for a unique cysteine at position 110 (Cys(110)). Adding hydrogen peroxide (H(2)O(2)) to human Mb affords Trp(14)-peroxyl, Tyr(103)-phenoxyl, and Cys(110)-thiyl radicals and coupling of Cys(110)-thiyl radicals yields a homodimer through intermolecular disulfide bond formation (Witting, P. K., Douglas, D. J., and Mauk, A. G. (2000) J. Biol. Chem. 275, 20391-20398). Treating a solution of wild type Mb and H(2)O(2) with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) at DMPO:protein </= 10 mol/mol yields DMPO-Cys(110) adducts as determined by EPR. At DMPO:protein ratios (25-50 mol/mol), both DMPO-Tyr(103) and DMPO-Cys(110) adducts were detected, whereas at DMPO:protein >/= 100 mol/mol only DMPO-Tyr(103) radicals were present. The DMPO-dependent decrease in DMPO-Cys(110) was matched by a near 1:1 stoichiometric increase in DMPO-Tyr(103). In contrast, reaction of the Y103F human Mb with H(2)O(2) gave no DMPO-Cys(110) at DMPO:protein </= 10 mol/mol, and only trace DMPO-Cys(110) at DMPO:protein >/= 100 mol/mol (i.e. conditions that consistently gave DMPO-Tyr(103) in the case of wild type Mb). No detectable homodimer was formed by incubation of the Y103F variant with H(2)O(2). However, the homodimer was detected in a mixture of both the Y103F and C110A variants of human Mb upon treatment with H(2)O(2) (C110A:Y103F:H(2)O(2) 2:1:5 mol/mol/mol); the yield of this homodimer increased with increasing ratios of C110A:Y103F. Together, these data suggest that addition of H(2)O(2) to human Mb can produce Cys(110)-thiyl radicals through an intermolecular electron transfer reaction from Cys(110) to a Tyr(103)-phenoxyl radical.
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Affiliation(s)
- P K Witting
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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